Assertion-Reasoning Based MCQ
Code
- 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.
Answer-b
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