NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current includes answers of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. It is important for the students to go through these NCERT solutions to get knowledge of the type of question asked on Chemical reactions and equations chapter.
Page No: 224
1. Why does a compass needle get deflected when brought near a bar magnet?
Answer
The needle of a compass is a small magnet. That’s why when a compass needle is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet. Hence, a compass needle gets deflected.
Page No: 228
Answer
Magnetic field lines of a bar magnet emerge from the north pole and terminate at the south pole. Inside the magnet, the field lines emerge from the south pole and terminate at the north pole, as shown in the given figure.
2. List the properties of magnetic lines of force.
Answer
The properties of magnetic lines of force are as follows.
→ Magnetic field lines emerge from the north pole.
→ They merge at the south pole.
→ The direction of field lines inside the magnet is from the south pole to the north pole.
→ Magnetic lines do not intersect with each other.
3. Why don’t two magnetic lines of force intersect each other?
Answer
The two magnetic field lines do not intersect each other because if they do it means at the point of intersect the compass needle is showing two different directions which is not possible.
Page No: 229
1. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Inside the loop = Pierce inside the table
Outside the loop = Appear to emerge out from the table
For downward direction of current flowing in the circular loop, the direction of magnetic field lines will be as if they are emerging from the table outside the loop and merging in the table inside the loop. Similarly, for upward direction of current flowing in the circular loop, the direction of magnetic field lines will be as if they are emerging from the table outside the loop and merging in the table inside the loop, as shown in the given figure.
2. The magnetic field in a given region is uniform. Draw a diagram to represent it.
(b) decreases as we move towards its end
(c) increases as we move towards its end
(d) is the same at all points
(a) mass
(b) speed
(c) velocity
(d) momentum
Answer
The displacement of rod AB is increased due to magnetic force exerted on it, if :
(i) If the current in the rod is increased then rod will be deflected with greater force.
(ii) If a stronger horse-shoe magnet is used then also rod will be deflected with greater force due to the increase in magnetic field.
(iii) If the length of the rod AB is increased.
(a) towards south
(b) towards east
(c) downward
(d) upward
Fleming’s left hand rule states that if we arrange the thumb, the centre finger, and the forefinger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the centre finger gives the direction of current, and the forefinger points in the direction of magnetic field.
2. What is the principle of an electric motor?
Answer
The principle of an electric motor is based on the magnetic effect of electric current. A current-carrying loop experiences a force and rotates when placed in a magnetic field. The direction of rotation of the loop is according to the Fleming’s left-hand rule.
3. What is the role of the split ring in an electric motor?
Page No: 236
1. Explain different ways to induce current in a coil.
Answer
The different ways to induce current in a coil are as follows:
→ If a coil is moved rapidly between the two poles of a horse-shoe magnet, then an electric current is induced in the coil.
→ If a magnet is moved relative to a coil, then an electric current is induced in the coil.
Page No: 237
1. State the principle of an electric generator.
Answer
Electric generator works on the principle of electromagnetic induction. Electricity is generated by rotating a coil inside magnetic field.
2. Name some sources of direct current.
Answer
Some sources of direct current are cell, DC generator, etc.
3. Which sources produce alternating current?
Answer
AC generators, power plants, etc., produce alternating current.
4. Choose the correct option.
(b) one revolution
(c) half revolution
(d) one-fourth revolution
► (c) half revolution
Page No: 238
1. Name two safety measures commonly used in electric circuits and appliances.
Answer
Two safety measures commonly used in electric circuits and appliances are
→ Electric Fuse: An electric fuse is connected in series it protects the circuit from overloading and prevents it from short circuiting.
→ Proper earthing of all electric circuit in which any leakage of current in an electric appliance is transferred to the ground and people using the appliance do not get the shock.
P = VI
Current = I
Power of the oven, P = 2 kW = 2000 W
Voltage supplied, V = 220 V
Hence, the current drawn by the electric oven is 9.09 A, which exceeds the safe limit of the circuit. Fuse element of the electric fuse will melt and break the circuit.
3. What precaution should be taken to avoid the overloading of domestic electric circuits?
Answer
The precautions that should be taken to avoid the overloading of domestic circuits are as follows:
→ Too many appliances should not be connected to a single socket.
→ Too many appliances should not be used at the same time.
→ Faulty appliances should not be connected in the circuit.
→ Fuse should be connected in the circuit.
1. Which of the following correctly describes the magnetic field near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire
(b) The field consists of straight lines parallel to the wire
(c) The field consists of radial lines originating from the wire
(d) The field consists of concentric circles centred on the wire
► (d) The field consists of concentric circles centred on the wire
2. The phenomenon of electromagnetic induction is
(a) the process of charging a body
(b) the process of generating magnetic field due to a current passing through a coil
(c) producing induced current in a coil due to relative motion between a magnet and the coil
(d) the process of rotating a coil of an electric motor
► (c) producing induced current in a coil due to relative motion between a magnet and the coil
3. The device used for producing electric current is called a
(a) generator
(b) galvanometer
(c) ammeter
(d) motor
► (a) generator
4. The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
► (d) AC generator has slip rings while the DC generator has a commutator.
5. At the time of short circuit, the current in the circuit
(a) reduces substantially
(b) does not change
(c) increases heavily
(d) vary continuously
► (c) increases heavily
6. State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
► False
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of an electric supply.
Live wire has red insulation cover, whereas earth wire has green insulation colour in the domestic circuits.
7. List three sources of magnetic fields.
Answer
→ Current-carrying conductors
→ Permanent magnets
→ Electromagnets
Page No: 241
8. How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Answer
A solenoid is a long coil of circular loops of insulated copper wire. Magnetic field lines are produced around the solenoid when a current is allowed to flow through it. The magnetic field produced by it is similar to the magnetic field of a bar magnet. The field lines produced in a current-carrying solenoid is shown in the following figure.
Answer
The force experienced by a current-currying conductor is the maximum when the direction of current is perpendicular to the direction of the magnetic field.
10. Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
Answer
The direction of the magnetic field is vertically downwards. The direction of current is from the front wall to the back wall because negatively charged electrons are moving from back wall to the front wall. The direction of magnetic force is rightward. Hence, using Fleming’s left hand rule, it can be concluded that the direction of magnetic field inside the chamber is downward.
11. Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
Answer
After half a rotation, the position of MN and ST interchange. The half-ring D comes in contact with brush A and half-ring C comes in contact with brush B. Hence, the direction of current in the coil MNST gets reversed.
The current flows through the coil in the direction TSNM. The reversal of current through the coil MNST repeats after each half rotation. As a result, the coil rotates unidirectional.
Answer
Some devices in which electric motors are Water pumps, Electric fans, Electric mixers and Washing machines.
13. A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?
Answer
(i) The needle of the galvanometer shows a momentary deflection in a particular direction.
(ii) The needle of the galvanometer shows a momentarily in the opposite direction.
(iii) The needle of the galvanometer shows no deflection.
14. Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
Answer
Two circular coils A and B are placed close to each other. When the current in coil A is changed, the magnetic field associated with it also changes. As a result, the magnetic field around coil B also changes. This change in magnetic field lines around coil B induces an electric current in it. This is called electromagnetic induction.
15. State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.
Answer
(i) Maxwell’s right hand thumb rule
(ii) Fleming’s left hand rule
(iii) Fleming’s right hand rule
16. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
Answer
Principle: An electric generator works on the principle of electromagnetic induction phenomenon. According to it, whenever a coil is rotated between the poles of a magnet, an induced current is set up in the coil, whose direction is given by Fleming’s right hand rule.
After half a rotation, arm AB starts moving down and the arm CD upward. Therefore, directions of induced currents in these arms change. Thus net induced current now becomes in the direction DCBA. In the external circuit now current flows from B1 to B2. Thus after every half rotation current changes its direction and an alternating current is obtained from the generator.
Function of Brushes: Brushes are kept pressed on the two slip rings separately. Outer ends of the brushes are connected to the galvanometer (or the external load). Thus brushes help in transferring current from the coil ABCD to the external circuit.
17. When does an electric short circuit occur?
Answer
If the insulation of the wires used in the circuit is damaged or the appliance used is faulty due to which the live wire and the neutral wire comes in direct contact as a result current in the circuit rises and the short circuit occurs.
18. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Answer
The metallic body of electric appliances is connected to the earth by means of earth wire so that any leakage of electric current is transferred to the ground. This prevents any electric shock to the user. That is why earthing of the electrical appliances is necessary.
Important Links
Quick Revision Notes – Chapter 13 Magnetic Effects of Electric Current
Most Important Questions- Chapter 13 Magnetic Effects of Electric Current
Important MCQs- Chapter 13 Magnetic Effects of Electric Current
Discover more from EduGrown School
Subscribe to get the latest posts sent to your email.