Both assertion and reason are true and reason is the correct explanation of assertion.
Both assertion and reason are true but reason is not the correct explanation of assertion.
Assertion is true but reason is false.
Assertion is false but reason is true.
1. Assertion AC is more dangerous in use than DC
Reason It is because the peak value of AC is greater than indicated value
2. Assertion Average value of AC over a complete cycle is always zero
Reason average value of AC is always defined over half cycle
3. Assertion The alternating current lags behind the EMF by a phase angle of when AC flows through and inductor
Reason The inductive reactance increases as the frequency of AC source decreases
4. Assertion Capacitor serves as a block for DC and offers an easy path to AC
Reason Capacitive reactance is inversely proportional to frequency
5. Assertion In series LCR resonant circuit the impedance is equal to the ohmic resistance
Reason At resonance the inductive reactance exceeds the capacitive reactance
6. Assertion An alternating current shows magnetic effect
Reason Alternating current varies with time
7. Assertion In series LCR circuit resonance can take place
Reason Resonance takes place in inductance and capacitive reactance are equal and opposite
8. Assertion Power factor correction is must in heavy machinery
Reason A low power factor implies larger power loss in transmission
9. Assertion Choke coil is preferred over a registered to adjust current in an AC circuit
Reason Power factor for inductance is zero
10. Assertion When AC circuit containing resistor only its power is minimum
Reason Power of a circuit is independent of phase angle
11. Assertion A transformer cannot work on DC supply
Reason DC change is neither in magnitude nor in direction
12. Assertion A laminated core is used in transformer to increase eddy currents
Reason The efficiency of a transformer increases with increase in eddy currents
13. Assertion Soft iron is used as a core of transformer
Reason Area of hysteresis loop for soft iron is small
14. Assertion An AC generator is based on the phenomenon of electromagnetic induction
Reason In single coil we consider self induction only
Assertion-Reasoning Based MCQAnswers
1. (1)
AC is more dangerous in use than DC. It is because the peak value of AC is greater than the indicated value.
2. (2)
The mean or average value of alternating current or EMF during half cycle is given by
Im = 0.636 Io Em = 0.6363 Eo
During the next half cycle, the mean value of AC will be equal in magnitude but opposite in direction. For this reason the average value of AC over a complete cycle is always zero. So the average value is always defined over a half cycle of AC.
3. (3)
When AC flows through an inductor current lags behind the EMF, by phase of π/2 inductive reactance
XL = ωL = 2πfL
So, when frequency increases correspondingly inductive reactance also increases.
4. (1)
The capacitive reactance of capacitor is given by
XC = 1/ ωC = 1/2πfC
So this is infinite for DC and has a very small value for AC. Hence, a capacitor blocks DC.
5. (3)
In series resonance circuit inductive reactance is equal to capacitive reactance.
ωL = 1/ωC
Z = R
6. (2)
Like direct current, an AC also produces magnetic field. But the magnitude and direction of the field goes on changing continuously with time.
7. (1)
At resonant frequency,
XL = XC, Z = R (minimum)
8. (2)
A heavy machinery requires a large power.
The average power is given by,
Pav = ErmsIrmscosΦ
The required power can be supplied to the heavy machinery either by supplying larger current or by improving power factor. The first method is costly. Hence, the second one is used.
9. (1)
We can use a capacitor of suitable capacitance as a choke coil, because average power consumed per cycle in an ideal capacitor is zero. Therefore, like a choke coil a condenser can reduce AC without power dissipation.
10. (4)
The power of an AC circuit is given by,
P = EIcosΦ
Where cosΦ is a power factor and is Φ phase angle. In case of circuit containing resistance only, phase angle is zero and power factor is equal to 1. Therefore power is maximum in case of circuit containing resistor only.
11. (1)
Transformer works on AC only AC changes in magnitude as well as in direction and induced EMF.
12. (4)
Large eddy currents are produced in non laminated iron core of the transformer by induced EMF, as the resistance of bulk iron core is very small. By using thin iron sheets are score the resistance is increased. Laminating the core substantially reduces the eddy currents. Eddy currents heat up the core of the transformer. More the eddy current greater the loss of energy and efficiency goes down.
13. (1)
Hysteresis loss in the core of transformer is directly proportional to the hysteresis loop area of the core material. Since soft iron has narrow hysteresis loop area, that is why soft iron core is used in transformer.
14. (2)
According to electromagnetic induction, whenever the magnetic flux changes and EMF will be induced in the coil.
Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses. (a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion. (b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion. (c) If the Assertion is correct but Reason is incorrect. (d) If both the Assertion and Reason are incorrect.
Q.1. Assertion : Induced emf will always occur whenever there is change in magnetic flux. Reason : Current always induces whenever there is change in magnetic flux.
Answer(c) Emf will always induces whenever, there is change in magnetic flux. The current will induced only in closed loop.
Q.2. Assertion : Faraday’s laws are consequence of conservation of energy. Reason : In a purely resistive ac circuit, the current legs behind the emf in phase.
Answer(c) In purely resistive circuit, the current and emf are in the same phase.
Q.3. Assertion : Only a change in magnetic flux will maintain an induced current in the coil. Reason : The presence of large magnetic flux through a coil maintain a current in the coil of the circuit is continuous.
Answer(c)
Q.4. Assertion : Lenz’s law violates the principle of conservation of energy. Reason : Induced emf always opposes the change in magnetic flux responsible for its production.
Answer(a) Lenz’s law (that the direction of induced emf is always such as to oppose the change that cause it) is direct consequence of the law of conservation of energy.
Q.5. Assertion : An induced current has a direction such that the magnetic field due to the current opposes the change in the magnetic flux that induces the current. Reason : Above statement is in accordance with conservation of energy.
Answer(b)
Q.6. Assertion : Acceleration of a magnet falling through a long solenoid decreases. Reason : The induced current produced in a circuit always flow in such direction that it opposes the change to the cause that produced it.
Answer(a)
Q.7. Assertion : Figure shows a horizontal solenoid connected to a battery and a switch. A copper ring is placed on a smooth surface, the axis of the ring being horizontal. As the switch is closed, the ring will move away from the solenoid.
Reason : Induced emf in the ring, e=-dΦ/dt
Answer(a)When switch is closed , the magnetic flux through the ring will increase and so ring will move away form the solenoid so as to compensate this flux. This is according to Lenz’s law.
Q.8. Assertion : An emf can be induced by moving a conductor in a magnetic field. Reason : An emf can be induced by changing the magnetic field.
Answer(b) In both the cases, the magnetic flux will change, and so there is an induced current.
Q.9. Assertion : Figure shows a metallic conductor moving in magnetic field. The induced emf across its ends is zero.
Reason : The induced emf across the ends of a conductor is given by e = Bvℓ sinθ.
Answer(a)
Q.10. Assertion : Eddy currents are produced in any metallic conductor when magnetic flux is changed around it. Reason : Electric potential determines the flow of charge.
Answer(b) Both the statements are independently correct.
Q.11. Assertion : An induced emf appears in any coil in which the current is changing. Reason : Self induction phenomenon obeys Faraday’s law of induction.
Answer(b)
Q.12. Assertion : When number of turns in a coil is doubled, coefficient of self-inductance of the coil becomes 4 times. Reason : This is because L α N2.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true, but reason is not the correct explanation of assertion.
If the assertion is true, but the reason is false.
If the assertion is false, but the reason is true.
1 . Assertion When a magnetic dipole is placed in a non uniform magnetic field, only a torque acts on the dipole.
Reason Force wouldn’t act on dipole if magnetic field were uniform.
2. Assertion Magnetic moment of helium atom is zero.
Reason All the electron are paired in helium atom orbitals.
3. Assertion Gauss theorem is not applicable in magnetism.
Reason Mono magnetic poles do not exist.
4. Assertion The true geographic north direction is found by using a compass needle.
Reason The magnetic meridian of the earth is along the axis of rotation of the earth.
5. Assertion In the northern hemisphere the north pole of the dip needle dips downwards.
Reason The north pole of earth is as a bar magnet lies in the northern hemisphere.
6. Assertion If a compass needle be kept at magnetic north pole of the earth, the compass needle mat stay in any direction.
Reason Dip needle will stay vertical at the north pole of earth.
7. Assertion To protect any instrument from external magnetic field, it is put inside an iron box.
Reason Iron is a magnetic substance.
Assertion-Reasoning Based MCQ Answers
1 . (4)
In a non uniform magnetic field, both a torque and a net force acts on the dipole. If magnetic field were uniform, net force on dipole would be zero.
2. (1)
Helium atom has paired electrons so their electron spin are opposite to each other and hence its net magnetic moment is zero.
3. (1)
The magnetic flux through any closed surface is zero.
4. (4)
The compass needle enables us to locate magnetic north pole. If magnetic declination at that particular place is known, then true geographic north-south direction can be located. Magnetic meridian is the vertical plane passing through magnetic axis. Magnetic axis is inclined at a certain angle θ to geographical axis and earth rotates about geographic axis.
5. (3)
In the northern hemisphere, magnetic needle comes to rest along north-south direction. So, that a greater dip angle is expected in northern hemisphere.
6. (2)
At magnetic poles of the earth, the only vertical component of the earth’s field acts, horizontal component is zero. A compass needle is free to rotate in horizontal plane and is affected by horizontal component only. Thus there will be no effect on the magnetic field on the compass needle. So the needle may stop in any direction. The angle of dip at the magnetic north pole is 90° and therefore the dip needle will become vertical.
7. (2)
Iron is ferromagnetic in nature. Lines of force due to external magnetic field prefer to pass through iron.
Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses.
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion. (b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion. (c) If the Assertion is correct but Reason is incorrect. (d) If both the Assertion and Reason are incorrect.
Q.1. Assertion : We cannot think of a magnetic field configuration with three poles Reason : A bar magnet does exert a torque on itself due to its own field.
Answer-d
Q.2. Assertion : In high latitudes one sees colourful curtains of light hanging down from high altitudes Reason : The high energy charged particles from the sun are deflected to polar regions by the magnetic field of the earth.
Answera
Q.3. Assertion : The true geographic north direction is found by using a compass needle. Reason : The magnetic meridian of the earth is along the axis of rotation of the earth.
Answer-d
Q.4. Assertion : A disc-shaped magnet is deviated above a superconducting material that has been cooled by liquid nitrogen. Reason : Superconductors repel a magnet.
Answer-a
Q.5. Assertion : Magnetic Resonance Imaging (MRI) is a useful diagnostic tool for producing images of various parts of human body. Reason : Protons of various tissues of the human body play a role in MRI.
Answer-a
Q.6. Assertion : Diamagnetic materials can exhibit magnetism. Reason : Diamagnetic materials have permanent magnetic dipole moment.
Answer-c
Q.7. Assertion : Ferro-magnetic substances become paramagnetic above Curie temp. Reason : Domains are destroyed at high temperature.
Answer-a
Q.8. Assertion : If a compass needle be kept at magnetic north pole of the earth the compass needle may stay in any direction. Reason : Dip needle will stay vertical at the north pole of earth
Answer-b
Q.9. Assertion : The ferromagnetic substance do not obey Curie’s law. Reason : At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.
Answer-b
Q.10. Assertion : The ferromagnetic substance do not obey Curie’s law. Reason : At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.
Answer-c
Q.11. Assertion : A paramagnetic sample display greater magnetisation (for the same magnetic field) when cooled. Reason : The magnetisation does not depend on temperature.
Answer-d
Q.12. Assertion : Electromagnetic are made of soft iron. Reason : Coercivity of soft iron is small.
Answer-b
Q.13. Assertion : The sensitivity of a moving coil galvanometer is increased by placing a suitable magnetic material as a core inside the coil. Reason : Soft iron has high magnetic permeability and cannot be easily magnetized or demagnetized.
Answer-c
Q.14. Assertion : The poles of magnet can not be separated by breaking into two pieces. Reason : The magnetic moment will be reduced to half when a magnet is broken into two equal pieces.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true, but reason is not the correct explanation of assertion.
If the assertion is true, but the reason is false.
If the assertion is false, but the reason is true.
1 . Assertion When a test charge moves through the magnetic field, its momentum changes but kinetic energy remains same.
Reason The magnetic force acts as a centripetal force, which is perpendicular to the instantaneous velocity and so does no work.
1 . (1)
Kinetic energy of the charged particle remains same in the circular path while velocity and momentum of the particle changes because of continous change in the direction of motion.
2. Assertion Magnetic field interacts with a moving charge.
Reason A moving charge produces a magnetic field.
2. (1)
A moving charge experience a force in magnetic field. It is because of interaction of two magnetic fields, one which is produced due to the motion of charge and other in which charge is moving.
3. Assertion Free electron always keeps on moving in a conductor even then no magnetic force act on them in magnetic field unless a current is passed through it.
Reason The average velocity of free electron is zero.
3. (1)
In the absence of electric field, the free electron in a conductor are in a state of random motion, like molecules in a gas. Their average velocity is zero, i.e, they do not have any net magnetic force on the free electrons in the magnetic field. On passing the current, the free electrons acquire drift velocity in a definite direction, hence magnetic force acts on them, unless the field has no perpendicular component.
4. Assertion Two beam of electrons traveling in the same direction repel each other.
Reason The electrostatic interaction is less than the magnetic interaction.
4. (3)
Two beams of electron traveling in the same direction repel each other because the electrostatic interaction is more that the magnetic interaction.
5. Assertion If the current in a solenoid is reversed in direction while keeping the same magnitude, the magnetic field energy stored in the solenoid decreases.
Reason Magnetic field energy density is proportional to square of current.
5. (4)
Reversing the direction of the current reverses the direction of magnetic field. However, it has no effect on the magnetic field energy density, which is proportional to the square of the magnitude interaction.
6. Assertion The magnetic field produced by a current carrying solenoid is independent of its length and cross-sectional area.
Reason The magnetic field inside the solenoid is uniform.
6. (2)
The earth’s magnetic field is towards north and the velocity of electron is vertically downward. Applying Fleming’s left hand rule, the direction of force is towards west. Therefore, an electron coming from outer space will be deflected toward west.
7. Assertion If two long wire, hanging freely an connected to a battery in series, they come closer to each other.
Reason Force of attraction acts between the two wires carrying current.
7. (4)
When two long parallel wires, are connected to a battery in series. They carry current in opposite directions, hence they repel each other.
8. Assertion In a shunted galvanometer only 10% current passes through the galvanometer. The resistance of the galvanometer is G. Then resistance of the shunt in G/9.
Reason If S is the resistance of the shunt, then voltage across S and G is same.
8. (2)
IgG = (I-Ig)S
S = (Ig / I – Ig) G
Ig = I / 10
S = G / 9
9. Assertion To convert a galvanometer into an ammeter a small resistance is connected in parallel with it.
Reason The small resistance increases the combined resistance of the combination.
9. (3)
An ammeter should have a low resistance which we get when we connect low resistance in parallel with galvanometer.
10. Assertion An ammeter is always connected in series whereas a voltmeter is connected in parallel.
Reason An ammeter is a low resistance galvanometer while a voltmeter is high resistance galvanometer.
10. (1)
An ammeter is a low resistance device and is connected in series so as the whole circuit current flows through it for an accurate measurement. A voltmeter is a device having a high resistance. So, if we connect it in series, it would hinder the current flow in the circuit hence open circuit results.
Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses. (a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion. (b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion. (c) If the Assertion is correct but Reason is incorrect. (d) If both the Assertion and Reason are incorrect.
Q.1. Assertion : In a simple battery circuit, the point of the lowest potential is positive terminal of the battery. Reason : The current flows towards the point of the higher potential, as it does in such a circuit from the negative to the positive terminal.
Answer-d
Q.2. Assertion : A larger dry cell has higher emf. Reason : The emf of a dry cell is proportional to its size.
Answer-d
Q.3. Assertion : A current continues to flow in superconducting coil even after switch is off. Reason : Superconducting coils show Meissner effect.
Answer-b
Q.4. Assertion : Voltmeter is connected in parallel with the circuit. Reason : Resistance of a voltmeter is very large.
Answer-b
Q.5. Assertion : Ohm’s law is applicable for all conducting elements. Reason : Ohm’s law is a fundamental law.
Answer-c
Q.6. Assertion : An electric bulb becomes dim, when the electric heater in parallel circuit is switched on. Reason : Dimness decreases after sometime.
Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses. (a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion. (b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion. (c) If the Assertion is correct but Reason is incorrect. (d) If both the Assertion and Reason are incorrect.
Q.1. Assertion : If the distance between parallel plates of a capacitor is halved and dielectric constant is three times, then the capacitance becomes 6 times. Reason : Capacity of the capacitor does not depend upon the nature of the material.
Answer-c
Q.2. Assertion : A parallel plate capacitor is connected across battery through a key. A dielectric slab of dielectric constant K is introduced between the plates. The energy which is stored becomes K times. Reason : The surface density of charge on the plate remains constant or unchanged.
Answer-c
Q.3. Assertion : The total charge stored in a capacitor is zero. Reason : The field just outside the capacitor is σ/ε0 . (σ is the charge density).
Answer-c
Q.4. Assertion : The electrostatic force between the plates of a charged isolated capacitor decreases when dielectric fills whole space between plates. Reason : The electric field between the plates of a charged isolated capacitance increases when dielectric fills whole space between plates.
Answer-d
Q.5. Assertion : Two concentric charged shells are given. The potential difference between the shells depends on charge of inner shell. Reason : Potential due to charge of outer shell remains same at every point inside the sphere.
Answer-a
Q.6. Assertion : Two equipotential surfaces cannot cut each other. Reason : Two equipotential surfaces are parallel to each other.
Answer-c
Q.7. Assertion: The potential difference between any two points in an electric field depends only on initial and final position. Reason: Electric field is a conservative field so the work done per unit positive charge does not depend on path followed.
Answer-a
Q.8. Assertion : Electric field inside a conductor is zero. Reason: The potential at all the points inside a conductor is same.
Answer-b
Q.9. Assertion : Electric field is discontinuous across the surface of a spherical charged shell. Reason : Electric potential is continuous across the surface of a spherical charged shell.
Answer-b
Q.10. Assertion : Work done in moving a charge between any two points in an electric field is independent of the path followed by the charge, between these points. Reason: Electrostatic force is a non conservative force.
Answer-c
Q.11. Assertion : Two adjacent conductors of unequal dimensions, carrying the same positive charge have a potential difference between them. Reason : The potential of a conductor depends upon the charge given to it.
Answer-b
Q.12. Assertion : Electric potential and electric potential energy are different quantities. Reason : For a system of positive test charge and point charge electric potential energy = electric potential.
Answer(c) Potential and potential energy are different quantities and cannot be equated.
Q.13. Assertion : For a non-uniformly charged thin circular ring with net charge is zero, the electric field at any point on axis of the ring is zero. Reason : For a non-uniformly charged thin circular ring with net charge zero, the electric potential at each point on axis of the ring is zero.
Answer(d) For a non-uniformly charged thin circular ring with net zero charge, electric potential at each point on its axis is zero. Hence electric field at each point on its axis must be perpendicular to the axis. Therefore Assertion is false and Reason is true.
Q.14. Assertion : For a charged particle moving from point P to point Q, the net work done by an electrostatic field on the particle is independent of the path connecting point P to point Q. Reason : The net work done by a conservative force on an object moving along a closed loop is zero.
Answer-a
Q.15. Assertion : Polar molecules have permanent dipole moment. Reason : In polar molecules, the centres of positive and negative charges coincide even when there is no external field.
Answer-c
Q.16. Assertion : Dielectric polarisation means formation of positive and negative charges inside the dielectric. Reason: Free electrons are formed in this process.
Answer-c
Q.17. Assertion : In the absence of an external electric field, the dipole moment per unit volume of a polar dielectric is zero. Reason : The dipoles of a polar dielectric are randomly oriented.
Answer-a
Q.18. Assertion : For a point charge, concentric spheres centered at a location of the charge are equipotential surfaces. Reason : An equipotential surface is a surface over which potential has zero value.
Answer-c
Q.19. Assertion : Electric energy resides out of the spherical isolated conductor. Reason : The electric field at any point inside the conductor is zero.
Answer(a) As these is no electric field inside the conductor, and so no energy inside it.
Q.20. Assertion : Two equipotential surfaces cannot cut each other. Reason : Two equipotential surfaces are parallel to each other.
Answer(c) Reason is false because the work done in bringing a unit positive charge from infinity to a point in equatorial plane is equal and opposite for the two charges of the dipole.
Q.21. Assertion: Two equipotential surfaces can be orthogonal. Reason: Electric field lines are normal to the equipotential surface.
Answer(d) Two equipotential surfaces never intersect each other so they cannot be orthogonal.
Q.22. Assertion: The equatorial plane of a dipole is an equipotential surface. Reason: The electric potential at any point on equatorial plane is zero.
Answer-b
Q.23. Assertion: The electric potential at any point on the equatorial plane of a dipole is zero. Reason: The work done in bringing a unit positive charge from infinity to a point in equatorial plane is equal for the two charges of the dipole.
Answer-d
Q.24. Assertion : A parallel plate capacitor is connected across battery through a key. A dielectric slab of dielectric constant k is introduced between the plates. The energy stored becomes k times. Reason : The surface density of charge on the plate remains constant.
Answer-c
Q.25. Assertion : Two metal plates having charges Q, –Q face each other at some separation and are dipped into an oil tank. If the oil is pumped out, the electric field between the plates increases. Reason : Electric field between the plates, Emed = Eair/K
Answer-c
Q.26. Assertion : When a dielectric slab is gradually inserted between the plates of an isolated parallel-plate capacitor, the energy of the system decreases. Reason : The force between the plates decreases.
Answer-c
Q.27. Assertion : A dielectric is inserted between the plates of a battery connected capacitor. The energy of the capacitor increases. Reason : Energy of the capacitor, U=CV2/2
Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses. (a) Both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion. (b) Both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion. (c) Assertion is correct, Reason is incorrect (d) Both Assertion and Reason are correct.
Q.1. Assertion: Electron move away from a region of lower potential to a region of higher potential. Reason: An electron has a negative charge.
Answer-a
Q.2. Assertion : A metallic shield in form of a hollow shell may be built to block an electric field. Reason : In a hollow spherical shield, the electric field inside it is zero at every point.
Answer-a
Q.3. Assertion : Electric lines of force never cross each other. Reason : Electric field at a point superimpose to give one resultant electric field.
Answer-b
Q.4.Assertion : The Coulomb force is the dominating force in the universe. Reason : The Coulomb force is weaker than the gravitational force.
Answer-d
Q.5. Assertion : In a cavity within a conductor, the electric field is zero. Reason : Charges in a conductor reside only at its surface.
Answer-a
Q.6. Assertion : When bodies are charged through friction, there is a transfer of electric charge from one body to another, but no creation or destruction of charge. Reason : This follows from conservation of electric charges.
Answer(a) Conservation of electric charge states that the total charge of an isolated system remains unchanged with time
Q.7. Assertion : The tyres of aircraft are slightly conducting. Reason : If a conductor is connected to ground, the extra charge induced on conductor will flow to ground.
Answer(b) Both the statements are independently correct.
Q.8. Assertion : Some charge is put at the centre of a conducting sphere. It will move to the surface of the sphere. Reason : Conducting sphere has no free electrons at the centre.
Answer(a) Because of repulsion, the free electrons will mole to the outer surface.
Q.9. Assertion : Coulomb force and gravitational force follow the same inverse-square law. Reason : Both laws are same in all aspects.
Answer(c) Coulomb force and gravitational force follow the same inverse-square law. But gravitational force has only one sign which is always attractive, while coulomb force can be of both signs which are attractive and repulsive.
Q.10. Assertion : The coulomb force is the dominating force in the universe. Reason : The coulomb force is weaker than the gravitational force.
Answer(d) Gravitational force is the dominating force in nature and not coulomb’s force. Gravitational force is the weakest force. Also, Coulomb’s force > > gravitational force.
Q.11. Assertion : If there exists coulomb attraction between two bodies, both of them may not be charged. Reason : In coulomb attraction two bodies are oppositely charged.
Answer(b) Coulomb attraction exists even when one body is charged, and the other is uncharged.
Q.12. Assertion : A deuteron and an -particle are placed in an electric field. If F1 and F2 be the forces acting on them and a1 and a2 be their accelerations respectively then, a1 = a2. Reason : Forces will be same in electric field.
Answer-c
Q.13. Assertion : The property that the force with which two charges attract or repel each other are not affected by the presence of a third charge. Reason : Force on any charge due to a number of other charge is the vector sum of all the forces on that charge due to other charges, taken one at a time.
Answer(b) Force on any charge due to a number of other charges is the vector sum of all the forces on that charge due to the other charges, taken one at a time. The individual force are unaffected due to the presence of other charges. This is the principle of superposition of charges.
Q.14. Assertion : A metallic shield in form of a hollow shell may be built to block an electric field. Reason : In a hollow spherical shield, the electric field inside it is zero at every point.
Answer(a) The electrostatic shielding is possible by metallic conductor.
Q.15. Assertion : A point charge is brought in an electric field, the field at a nearby point will increase or decrease, depending on the nature of charge. Reason : The electric field is independent of the nature of charge.
Answer(c) The electric field will increase if positive charge is brought in an electric field.
Q.16. Assertion : Consider two identical charges placed distance 2d apart, along x-axis.
The equilibrium of a positive test charge placed at the point O midway between them is stable for displacements along the x-axis. Reason: Force on test charge is zero.
Answer(b) If +ve charge is displaced along x-axis, then net force will always act in a direction opposite to that of displacement and the test charge will always come back to its original position.
Q.17. Assertion : When a conductor is placed in an external electrostatic field, the net electric field inside the conductor becomes zero after a small instant of time. Reason : It is not possible to set up an electric field inside a conductor.
Answer(c) Statement-1 is correct. The induced field cancels the external field. Statement-2 is false. When a current is set up in a conductor, there exists an electric field inside it.
Q.18. Assertion : A uniformly charged disc has a pin hole at its centre. The electric field at the centre of the disc is zero. Reason : Disc can be supposed to be made up of many rings. Also electric field at the centre of uniformly charged ring is zero.
Answer(a) The electric field due to disc is superposition of electric field due to its constituent ring as given in Reason.
Q.19. Assertion : Electric lines of field cross each other. Reason : Electric field at a point superimpose to give one resultant electric field.
AnswerAssertion is Incorrect, Reason is correct. (d) Two field lines never intersect.
Q.20. Assertion : On bringing a positively charged rod near the uncharged conductor, the conductor gets attracted towards the rod. Reason : The electric field lines of the charged rod are perpendicular to the surface of conductor.
Answer(b) Though the net charge on the conductor is still zero but due to induction negatively charged region is nearer to the rod as compared to the positively charged region. That is why the conductor gets attracted towards the rod
Q.21. Assertion : Four point charges q1, q2, q3 and q4 are as shown in figure. The flux over the shown Gaussian surface depends only on charges q1 and q2.
Reason : Electric field at all points on Gaussian surface depends only on charges q1 and q2.
Answer(d) Electric field at any point depends on presence of all charges.
Q.22. Assertion : On disturbing an electric dipole in stable equilibrium in an electric field, it returns back to its stable equilibrium orientation. Reason : A restoring torque acts on the dipole on being disturbed from its stable equilibrium.
Answer(a) The restoring torque brings it back to its stable equilibrium.
Q.23. Assertion : On going away from a point charge or a small electric dipole, electric field decreases at the same rate in both the cases. Reason : Electric field is inversely proportional to square of distance from the charge or an electric dipole.
Answer(d)
Q.24. Assertion : The electric flux of the electric field ∮ E.dA is zero. The electric field is zero everywhere on the surface. Reason : The charge inside the surface is zero.
Answer(d)
Q.25. Assertion : On moving a distance two times the initial distance away from an infinitely long straight uniformly charged wire the electric field reduces to one third of the initial value. Reason : The electric field is inversely proportional to the distance from an infinitely long straight uniformly charged wire.
Answer(a)
Q.26. Assertion (A): No two electric lines of force can intersect each other. Reason (R) : Tangent at any point of electric line of force gives the direction of electric field.
Answer(a)
Q.27. Assertion (A): Electric force acting on a proton and an electron, moving in a uniform electric field is same, where as acceleration of electron is 1836 times that of a proton. Reason (R): Electron is lighter than proton.
Answer(a)
Q.28. Assertion (A): As force is a vector quantity, hence electric field intensity is also a vector quantity Reason (R): The unit of electric field intensity is newton per coulomb.
Answer(b)
Q.29. Assertion (A) : Sharper is the curvature of spot on a charged body lesser will be the surface charge density at that point Reason (R): Electric field is non-zero inside a charged conductor.
Answer(d)
Q.30. Assertion (A): The surface densities of two spherical conductors of different radii are equal. Then the electric field intensities near their surface are also equal. Reason (R) : Surface density is equal to charge per unit area.
Answer(b)
Q.31. Assertion (A): Three equal charges are situated on a circle of radius r such that they form on equilateral triangle, then the electric field intensity at the centre is zero. Reason (R): The force on unit positive charge at the centre, due to the three equal charges are represented by the three sides of a triangle taken in the same order. Therefore, electric field intensity at centre is zero.
Answer(a)
Q.32. Assertion (A): The electric lines of forces diverges from a positive charge and converge at a negative charge. Reason (A): A charged particle free to move in an electric field always move along an electric line of force.Answer(c)
Q.33. Assertion (A): Charging is due to transfer of electrons. Reason (R): Mass of a body decreases slightly when it is negatively charged.
Answer(c)
Q.34. Assertion (A): Range of Coulomb force is infinite. Reason (R): Coulomb force acts between two charged particles.
Answer(b)
Q.35. Assertion (A): A small metal ball is suspended in a uniform electric field with an insulated thread. If high energy X-ray beam falls on the ball, the ball will be deflected in the electric field. Reason (R): X-rays emits photoelectron and metal becomes negatively charged.
Answer(c)
Q.36. Assertion (A): If a point charge be rotated in a circle around a charge, the work done will be zero. Reason (R): Work done is equal to dot product of force and distance
In the questions given below, there are two Statements marked as Assertion (A) and Reason (R). Read the Statements and Choose the correct option: Options are: (A) Both (A) and (R) are true and (R) is the correct explanation of (A). (B) Both (A) and (R) are true but (R) is not the correct explanation of (A). (C) (A) is correct but (R) is wrong. (D) (A) is wrong but (R) is correct.
Q.1. Assertion: Food security exists when all people, at all times, have physical, social, and economic access to sufficient, safe, and nutritious food to meet their dietary needs and food preferences. Reason: Food security is a multi-dimensional concept that involves not only the availability of food but also access to food, utilization of food, and stability of food supply.
➤ Show AnswerAnswer: (A)
Q.2. Assertion: The Green Revolution helped to increase food production in India. Reason: The Green Revolution involved the introduction of high-yielding varieties of crops, modern irrigation techniques, and use of chemical fertilizers and pesticides, which led to increased food production.
➤ Show AnswerAnswer: (A)
Q.3. Assertion: Chronic hunger is a result of food shortages. Reason: Chronic hunger is a result of poverty and inequality, which limit people’s access to food.
➤ Show AnswerAnswer: (D) The assertion is false, but the reason is true. Chronic hunger is not only a result of food shortages but also a result of poverty, inequality, and other factors such as poor health, inadequate sanitation, and lack of education.
Q.4. Assertion: The National Food Security Act (NFSA) aims to provide food security to all people in India. Reason: The NFSA entitles poor households to receive 5 kg of food grains per person per month at subsidized prices under the PDS.
➤ Show AnswerAnswer: (A)
Q5. Assertion (A) : Food security, credit facilities guarantee social protection to the poor.
Reasoning (R) : Leakages in the administrative system perpetuates poverty.
