Class 10 Science · Chapter 12

Magnetic Effects of Electric Current

170 Class 10 Science questions on Magnetic Effects of Electric Current from the NCERT textbook, NCERT Exemplar and CBSE board papers 2023–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 2 of 9

1. Q21 NCERT · Intext Questions (Page 205)
   An electric oven of 2 ​kW ​power rating is operated in a domestic ​electric circuit ($220$ ​V) that has ​a current rating ​of $5$ ​A. What result do you expect? Explain.
   Show answer

   The oven would draw about 9.1 A, more than the 5 A rating, so the fuse melts and the oven does not work.

   The oven would draw a current of $I=P/V=2000/220\approx 9.1$ A, which is far more than the 5 A the circuit is rated for. The circuit is therefore overloaded. The fuse in its live wire, chosen for the 5 A rating, is heated by this large current, melts and breaks the circuit, so the supply to the oven is cut off and the oven does not work. This is the fuse doing its job: without it the wiring, designed for 5 A, would overheat and could cause a fire. The oven should be run instead on the 15 A circuit provided for high-power appliances.

   Step-by-step solution →
2. Q22 NCERT · Intext Questions (Page 205)
   What ​precaution ​should be taken to avoid ​the overloading ​of ​domestic ​electric circuits?
   Show answer

   Avoid too many appliances on one circuit, use circuits and fuses of correct rating, and keep the wiring and its insulation sound.

   To avoid overloading of domestic circuits: (i) Do not connect too many appliances to a single socket or to one circuit, since the currents they draw add up. (ii) Use separate circuits of suitable rating and put each appliance on the right one — high-power appliances such as geysers, air coolers and ovens on the 15 A circuit, and bulbs and fans on the 5 A circuit; never run an appliance on a circuit whose current rating is less than the current it draws. (iii) Fit a fuse or a miniature circuit breaker of the correct rating in series with the live wire of every circuit, and never replace it with one of a higher rating or with a piece of ordinary wire. (iv) Use good-quality wires with proper insulation and adequate current-carrying capacity, and repair damaged insulation and faulty appliances promptly, since the live and neutral wires touching cause a short circuit and a sudden rise of current. (v) Use a voltage stabiliser for sensitive appliances to guard against an accidental hike in the supply voltage, and switch off appliances that are not in use.

   Step-by-step solution →
3. Q23 Exemplar · Multiple Choice Questions
   Choose ​the incorrect ​statement ​from the following regarding magnetic ​lines of field

   1. (a)The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points
   2. (b)Magnetic field lines are closed curves
   3. (c)If magnetic field lines are parallel and equidistant, they represent zero field strength
   4. (d)Relative strength of magnetic field is shown by the degree of closeness of the field lines
   Show answer

   (c) If magnetic field lines are parallel and equidistant, they represent zero field strength

   Step-by-step solution →
4. Q24 Exemplar · Multiple Choice Questions
   If ​the key in ​the arrangement (Figure ​13.1) is taken out ​(the circuit is made open) and magnetic field lines are ​drawn over ​the horizontal plane ABCD, the lines are

   1. (a)concentric circles
   2. (b)elliptical in shape
   3. (c)straight lines parallel to each other
   4. (d)concentric circles near the point O but of elliptical shapes as we go away from it
   Show answer

   (c) straight lines parallel to each other

   Step-by-step solution →
5. Q25 Exemplar · Multiple Choice Questions
   A ​circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as ​seen from points ​A and B (in the plane of paper and on the axis of the coil) is anti clockwise and clockwise respectively. The magnetic ​field lines ​point from B ​to ​A. The N-pole of the resultant magnet is ​on the face close to

   1. (a)A
   2. (b)B
   3. (c)A if the current is small, and B if the current is large
   4. (d)B if the current is small and A if the current is large
   Show answer

   (a) A

   Step-by-step solution →
6. Q26 Exemplar · Multiple Choice Questions
   For a current ​in ​a ​long straight solenoid N- and S-poles are created at the two ends. ​Among the following ​statements, the incorrect ​statement is

   1. (a)The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid
   2. (b)The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil
   3. (c)The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet
   4. (d)The N- and S-poles exchange position when the direction of current through the solenoid is reversed
   Show answer

   (c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet

   Step-by-step solution →
7. Q27 Exemplar · Multiple Choice Questions
   A uniform magnetic field ​exists in the plane of ​paper pointing from left to right as shown in Figure ​13.3. In the field an electron and a proton move as shown. The electron ​and ​the ​proton experience

   1. (a)forces both pointing into the plane of paper
   2. (b)forces both pointing out of the plane of paper
   3. (c)forces pointing into the plane of paper and out of the plane of paper, respectively
   4. (d)force pointing opposite and along the direction of the uniform magnetic field respectively
   Show answer

   (a) forces both pointing into the plane of paper

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8. Q28 Exemplar · Multiple Choice Questions
   Commercial electric motors ​do not ​use

   1. (a)an electromagnet to rotate the armature
   2. (b)effectively large number of turns of conducting wire in the current carrying coil
   3. (c)a permanent magnet to rotate the armature
   4. (d)a soft iron core on which the coil is wound
   Show answer

   (c) a permanent magnet to rotate the armature

   Step-by-step solution →
9. Q29 Exemplar · Multiple Choice Questions
   In ​the arrangement shown in Figure 13.4 there are two coils wound on ​a non-conducting cylindrical rod. Initially the ​key is not inserted. Then the ​key is inserted ​and later removed. Then

   1. (a)the deflection in the galvanometer remains zero throughout
   2. (b)there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed
   3. (c)there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction
   4. (d)there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions
   Show answer

   (d) there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

   Step-by-step solution →
10. Q30 Exemplar · Multiple Choice Questions
    Choose the incorrect statement

    1. (a)Fleming's right-hand rule is a simple rule to know the direction of induced current
    2. (b)The right-hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors
    3. (c)The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically
    4. (d)In India, the AC changes direction after every $\frac{1}{50}$ second
    Show answer

    (d) In India, the AC changes direction after every $\frac{1}{50}$ second

    Step-by-step solution →
11. Q31 Exemplar · Multiple Choice Questions
    A constant current flows in a ​horizontal wire in the plane of the ​paper ​from ​east to west as shown in Figure 13.5. The direction ​of magnetic field ​at a point will be ​North ​to South

    1. (a)directly above the wire
    2. (b)directly below the wire
    3. (c)at a point located in the plane of the paper, on the north side of the wire
    4. (d)at a point located in the plane of the paper, on the south side of the wire
    Show answer

    (b) directly below the wire

    Step-by-step solution →
12. Q32 Exemplar · Multiple Choice Questions
    The strength of magnetic ​field ​inside a ​long ​current ​carrying straight solenoid ​is

    1. (a)more at the ends than at the centre
    2. (b)minimum in the middle
    3. (c)same at all points
    4. (d)found to increase from one end to the other
    Show answer

    (c) same at all points

    Step-by-step solution →
13. Q33 Exemplar · Multiple Choice Questions
    To convert ​an ​AC generator ​into ​DC ​generator

    1. (a)split-ring type commutator must be used
    2. (b)slip rings and brushes must be used
    3. (c)a stronger magnetic field has to be used
    4. (d)a rectangular wire loop has to be used
    Show answer

    (a) split-ring type commutator must be used

    Step-by-step solution →
14. Q34 Exemplar · Multiple Choice Questions
    The most important ​safety ​method used for protecting home ​appliances from ​short circuiting ​or overloading is

    1. (a)earthing
    2. (b)use of fuse
    3. (c)use of stabilizers
    4. (d)use of electric meter
    Show answer

    (b) use of fuse

    Step-by-step solution →
15. Q35 Exemplar · Short Answer Questions
    A magnetic ​compass ​needle is placed in the plane of ​paper ​near ​point A as shown in Figure 13.6. ​In which plane should a straight current carrying conductor be placed so that it passes through A ​and there is no change in the deflection of the compass? Under ​what condition is the deflection maximum and why?

    Show answer

    The conductor must lie in the plane of the paper for no change; the deflection is maximum when it is perpendicular to the paper.

    The conductor must be placed in the plane of the paper, that is, in the same plane as the compass needle. Its field at the needle is then perpendicular to the paper, and a needle free to swing only within the paper feels no turning effect from it, so the deflection is unchanged. The deflection is maximum when the conductor is placed perpendicular to the plane of the paper through A, because the circular field lines then lie in the paper itself and the whole of the field acts in the plane in which the needle turns. Since $B\propto I/r$, the deflection grows further if the current is increased or the compass is brought nearer to the conductor.

    Step-by-step solution →
16. Q36 Exemplar · Short Answer Questions
    Under ​what conditions permanent electromagnet is obtained if a current carrying ​solenoid is used? Support ​your answer ​with the help ​of ​a labelled circuit diagram.
    Show answer

    Use a steel core, pass a steady direct current, and make the field strong with many close turns and a large current.

    Two conditions must be met together. First, the rod placed inside the solenoid must be of a hard magnetic material such as steel rather than soft iron, because steel keeps its magnetism after the magnetising field is removed while soft iron loses nearly all of it. Second, the solenoid must carry a steady direct current, supplied by a battery, so that the magnetising field keeps one direction and definite N and S poles are established; with alternating current the field would reverse a hundred times a second and no settled poles would be left. The field must also be strong enough, which is why the solenoid is wound with a large number of close turns and carries a sufficiently large current. The circuit is the solenoid, wound on the steel rod, joined in series with a battery and a plug key, as drawn in the labelled diagram.

    Step-by-step solution →
17. Q37 Exemplar · Short Answer Questions
    AB ​is ​a current carrying ​conductor in the plane of the paper as ​shown in Figure 13.7. What ​are the directions of magnetic ​fields produced by it at points P and Q? Given $r_1>r_2$, where will the strength of the magnetic ​field be ​larger?

    Show answer

    At P the field is into the paper, at Q out of the paper; the field is stronger at Q, the nearer point.

    The current flows upwards, as the arrow on the conductor shows. At P, which lies to the right of the conductor, the magnetic field is directed into the plane of the paper; at Q, which lies to the left of it, the field is directed out of the plane of the paper. Since $B\propto 1/r$ for a straight conductor and $r_2<r_1$, the strength of the magnetic field is larger at Q.

    Step-by-step solution →
18. Q38 Exemplar · Short Answer Questions
    A ​magnetic compass shows a deflection when placed near ​a current carrying wire. How will the deflection of the compass get ​affected if ​the ​current in the wire is increased? ​Support ​your answer with a reason.
    Show answer

    The deflection increases, because the wire's field at the compass is proportional to the current.

    The deflection increases. The compass is not moved, so its distance from the wire is unchanged, and the field of a straight conductor at a fixed distance is directly proportional to the current, $B\propto I/r$. The needle rests along the resultant of that field and the earth's horizontal field. Raising the current lengthens the wire's contribution while the earth's field stays exactly as it was, so the resultant turns further away from the north-south direction and the needle deflects more. In the usual arrangement, in which the wire's field at the needle is at right angles to the earth's field, $\tan \theta =B/B_H$, so the tangent of the deflection grows in proportion to the current and the deflection itself approaches, but never reaches, a right angle.

    Step-by-step solution →
19. Q39 Exemplar · Short Answer Questions
    It is established that an electric current through ​a metallic conductor produces a magnetic ​field around ​it. Is ​there a similar magnetic field produced around ​a thin beam of moving

    1. (i)alpha particles, ​
    2. (ii)​neutrons? Justify your answer.
    Show answer

    Yes for alpha particles, because moving charge forms a current; no for neutrons, which carry no charge.

    (i) Yes. An alpha particle carries a charge of $+2e$, so a thin beam of moving alpha particles is a stream of moving charge, which is an electric current even though no wire is involved. A magnetic field is therefore produced around the beam, its lines forming circles that encircle the beam; since the particles are positive the conventional current is along the beam, and the right-hand thumb rule with the thumb pointing along the beam gives the sense of those circles. (ii) No. A neutron carries no charge at all, so however fast and however intense the beam is, no charge passes any point of it and it constitutes no current. With no current there is no magnetic field of this kind around a neutron beam.

    Step-by-step solution →
20. Q40 Exemplar · Short Answer Questions
    What ​does the ​direction of thumb ​indicate in ​the right-hand thumb rule. In ​what ​way this ​rule is different ​from Fleming's left-hand rule?
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    The thumb shows the direction of the current; the thumb rule gives the field produced by a current, Fleming's rule the force on it.

    In the right-hand thumb rule the direction of the thumb indicates the direction of the **current** in the straight conductor; the curled fingers then give the direction in which the magnetic field lines encircle it. The rule differs from Fleming's left-hand rule in four ways. It uses the right hand, while Fleming's rule uses the left. It involves only two directions, the current and the field, while Fleming's rule involves three mutually perpendicular directions, the field on the forefinger, the current on the centre finger and the force on the thumb. The thumb stands for the current in the first rule but for the force in the second. Most importantly, the right-hand thumb rule gives the magnetic field that a current **produces** around itself, whereas Fleming's left-hand rule gives the force that a current-carrying conductor **experiences** when it is placed in an external magnetic field.

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