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Class 10 · Science · Chapter 12: Magnetic Effects of Electric Current

BSEB Class 10 Science Chapter 12: Objective Questions (MCQ) with Answers

Bihar Board · NCERT · CBSE

All 58 objective questions (MCQ) of this chapter — solve first, then tap “Show answer”. Each question shows its source label: «BSEB 2025 · board paper» = verified from the official board paper; «Board-style (practice)» = Study With Me's own practice questions.

← Chapter 12: Magnetic Effects of Electric Current — full notes, video, questions

1Check

What is a compass needle?

  1. (A) An iron nail
  2. (B) A small bar magnet
  3. (C) A fuse
  4. (D) A copper wire
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Correct answer: (B) A small bar magnet

The needle is a small bar magnet. The end toward the north is the north pole.

2Check

What happens between like poles?

  1. (A) They attract
  2. (B) They repel
  3. (C) No force
  4. (D) Only heat
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Correct answer: (B) They repel

Like poles repel. Unlike poles attract.

3Check

Outside a bar magnet, field lines go which way?

  1. (A) South to north
  2. (B) North to south
  3. (C) Only upward
  4. (D) Straight and parallel to a wire
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Correct answer: (B) North to south

Outside, the lines go from the north pole to the south pole. Inside, the direction is from south to north.

4Check

What is the magnetic field near a long straight wire like?

  1. (A) Straight lines parallel to the wire
  2. (B) Straight lines perpendicular to the wire
  3. (C) Radial lines leaving the wire
  4. (D) Concentric circles centred on the wire
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Correct answer: (D) Concentric circles centred on the wire

The field is concentric circles. The circles get larger as the distance grows.

5Check

If the current is from north to south, which way does the north pole of the needle move?

  1. (A) East
  2. (B) West
  3. (C) Up
  4. (D) It does not move
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Correct answer: (A) East

For a current from north to south the north pole moves east. When the current is reversed it moves west.

6Check

How large is the field at the centre of a coil of n turns, compared with one turn?

  1. (A) Half
  2. (B) The same
  3. (C) n times
  4. (D) The inverse of n
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Correct answer: (C) n times

The field of n turns is n times the field of one turn.

7Check

In Activity 12.6, why are iron filings sprinkled?

  1. (A) To heat the coil
  2. (B) To show the pattern of the field
  3. (C) To measure the current
  4. (D) To melt a fuse
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Correct answer: (B) To show the pattern of the field

The iron filings settle in the pattern of the field lines.

8Check

What is the magnetic field inside a long solenoid like?

  1. (A) Zero
  2. (B) It decreases toward the end
  3. (C) It increases toward the end
  4. (D) The same at every point
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Correct answer: (D) The same at every point

The field inside is uniform, the same at every point.

9Check

When is the force on a current-carrying conductor the largest?

  1. (A) When current and field are parallel
  2. (B) When current and field are perpendicular
  3. (C) When the current is zero
  4. (D) When the field is zero
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Correct answer: (B) When current and field are perpendicular

The force is largest when the current is perpendicular to the magnetic field.

10Check

In Fleming left hand, what does the thumb show?

  1. (A) The field
  2. (B) The current
  3. (C) The force or the motion
  4. (D) The induced current
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Correct answer: (C) The force or the motion

The thumb shows the force or the motion. Induced current belongs to the middle finger of the right hand.

11Check

Which rule gives the induced current in a coil rotating in a magnetic field?

  1. (A) Fleming left hand
  2. (B) Fleming right hand
  3. (C) Ohm law alone
  4. (D) The right thumb, with no motion
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Correct answer: (B) Fleming right hand

Fleming right hand gives the direction of the induced current.

12Check

What is the basic idea in a generator?

  1. (A) A coil rotates in a field and a current is induced
  2. (B) A fuse melts
  3. (C) Only a cell is connected
  4. (D) Field lines cross
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Correct answer: (A) A coil rotates in a field and a current is induced

In a generator a coil rotates in a magnetic field and a current is induced.

13Check

In a domestic supply the wire with green insulation is —

  1. (A) Live
  2. (B) Neutral
  3. (C) Earth
  4. (D) Only the fuse
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Correct answer: (C) Earth

The green wire is the earth. It is not live.

14Check

About how much current does a 2 kW oven draw at 220 V?

  1. (A) 0.9 A
  2. (B) 2 A
  3. (C) 9.1 A
  4. (D) 440 A
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Correct answer: (C) 9.1 A

I = 2000/220 = 9.09 A, about 9.1 A. That is above the 5 A rating.

15BSEB 2025 · board paper · Q18 · page 91 mark

Who propounded the «right-hand thumb» rule?

  1. (A) Maxwell
  2. (B) Einstein
  3. (C) Fleming
  4. (D) Oersted
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Correct answer: (A) Maxwell

The right-hand thumb rule for the field of a straight current-carrying wire is also called Maxwell's corkscrew rule. Fleming's rules are for force and induced current; Oersted discovered the magnetic effect of current (lesson 3).

16BSEB model paper 2026 (not the annual exam) · Q21 · page 91 mark

Who discovered the magnetic effect of electric current?

  1. (A) Oersted
  2. (B) Ampere
  3. (C) Bohr
  4. (D) Faraday
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Correct answer: (A) Oersted

Hans Christian Oersted saw in 1820 that a compass needle turns near a current-carrying wire (lesson 1).

17BSEB model paper 2026 (not the annual exam) · Q22 · page 91 mark

The nature of magnetic field lines is—

  1. (A) Imaginary
  2. (B) Real
  3. (C) Both A and B
  4. (D) None of these
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Correct answer: (A) Imaginary

Field lines are an imaginary way to show a field — iron filings only show their pattern (lesson 2).

18BSEB model paper 2026 (not the annual exam) · Q23 · page 91 mark

The device for producing electric current is called—

  1. (A) Generator
  2. (B) Galvanometer
  3. (C) Ammeter
  4. (D) Motor
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Correct answer: (A) Generator

A generator makes current from mechanical energy; a motor does the reverse — electrical to mechanical (lesson 7).

19BSEB model paper 2026 (not the annual exam) · Q24 · page 91 mark

Resistance of the circuit at the time of short circuit—

  1. (A) does not change
  2. (B) decreases considerably
  3. (C) increases very much
  4. (D) none of these
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Correct answer: (B) decreases considerably

In a short circuit the live and neutral wires touch directly, the resistance falls greatly, so the current rises sharply (NCERT exercise 2 asks this current) (lesson 8).

20Book-based · 12.1 · compass1 mark

What is a compass needle actually?

  1. (A) An iron nail
  2. (B) A small bar magnet
  3. (C) A copper wire
  4. (D) An electric cell
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Correct answer: (B) A small bar magnet

The needle is a small bar magnet; the end that points north is the north pole.

21Book-based · 12.1 · field lines1 mark

Outside a magnet, field lines go—

  1. (A) S to N
  2. (B) N to S
  3. (C) only at N
  4. (D) nowhere
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Correct answer: (B) N to S

Outside N to S, inside S to N — closed curves.

22Book-based · 12.1 · strength1 mark

Where is the field stronger?

  1. (A) Where lines are far apart
  2. (B) Where lines are crowded
  3. (C) Outside the lines
  4. (D) Equal everywhere
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Correct answer: (B) Where lines are crowded

Crowded lines = stronger field (at the poles).

23Book-based · 12.2.1 · straight wire1 mark

Field lines around a current-carrying straight wire are—

  1. (A) parallel straight lines
  2. (B) concentric circles
  3. (C) radial lines
  4. (D) ellipses
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Correct answer: (B) concentric circles

Concentric circles centred on the wire (Activity 12.5).

24Book-based · 12.2.1 · distance1 mark

As distance from the wire increases, the magnetic field—

  1. (A) increases
  2. (B) decreases
  3. (C) stays the same
  4. (D) reverses
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Correct answer: (B) decreases

Distance ⬆ → field ⬇.

25Book-based · 12.2.1 · Activity 12.41 mark

If current flows north to south over the needle, its north pole moves—

  1. (A) east
  2. (B) west
  3. (C) north
  4. (D) south
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Correct answer: (A) east

Book: for N → S current the N pole moves east; reverse it and it moves west.

26Book-based · 12.2.3 · loop1 mark

The field of a coil of n turns compared with one turn is—

  1. (A) n times
  2. (B) 1/n times
  3. (C) equal
  4. (D) zero
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Correct answer: (A) n times

Current in each turn is the same way → field n times.

27Book-based · 12.2.4 · solenoid1 mark

The field inside a long current-carrying solenoid is—

  1. (A) zero
  2. (B) decreasing towards the ends
  3. (C) increasing towards the ends
  4. (D) the same at all points
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Correct answer: (D) the same at all points

Parallel straight lines inside → a uniform field.

28Book-based · 12.2.4 · electromagnet1 mark

What is usually placed as the core of an electromagnet?

  1. (A) Copper
  2. (B) Soft iron
  3. (C) Aluminium
  4. (D) Wood
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Correct answer: (B) Soft iron

Soft iron — a magnet only while current flows.

29Book-based · 12.3 · force1 mark

When is the magnetic force on a current-carrying conductor largest?

  1. (A) Current parallel to the field
  2. (B) Current perpendicular to the field
  3. (C) Zero current
  4. (D) Zero field
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Correct answer: (B) Current perpendicular to the field

When I ⟂ B; the force is then perpendicular to both.

30Book-based · 12.3 · Fleming left hand1 mark

In Fleming's left-hand rule the forefinger shows—

  1. (A) current
  2. (B) force
  3. (C) magnetic field
  4. (D) motion
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Correct answer: (C) magnetic field

Forefinger = field, middle = current, thumb = force.

31Book-based · 12.3 · proton1 mark

Which property of a proton moving freely in a magnetic field can change?

  1. (A) Mass
  2. (B) Speed
  3. (C) Velocity
  4. (D) Charge
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Correct answer: (C) Velocity

The force changes direction → velocity (and momentum) change, not speed.

32Book-based · 12.4 · domestic circuit1 mark

The frequency of domestic supply in India is—

  1. (A) 50 Hz
  2. (B) 60 Hz
  3. (C) 220 Hz
  4. (D) 5 Hz
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Correct answer: (A) 50 Hz

220 V, 50 Hz AC.

33Book-based · 12.4 · neutral wire1 mark

The insulation colour of the neutral wire is—

  1. (A) red
  2. (B) black
  3. (C) green
  4. (D) yellow
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Correct answer: (B) black

Red = live, black = neutral, green = earth.

34NCERT in-text question · after 12.2 · Q31 mark

Choose the correct option. The magnetic field inside a long straight solenoid-carrying current

  1. (A) is zero
  2. (B) decreases as we move towards its end
  3. (C) increases as we move towards its end
  4. (D) is the same at all points
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Correct answer: (D) is the same at all points

Parallel straight lines inside → the same at all points (uniform).

35NCERT in-text question · after 12.3 · Q31 mark

A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is

  1. (A) towards south
  2. (B) towards east
  3. (C) downward
  4. (D) upward
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Correct answer: (D) upward

Motion of the positive charge = current (west), force = north. Fleming left hand: middle finger west, thumb north → forefinger upward.

36NCERT exercise · Q11 mark

Which of the following correctly describes the magnetic field near a long straight wire?

  1. (A) The field consists of straight lines perpendicular to the wire
  2. (B) The field consists of straight lines parallel to the wire
  3. (C) The field consists of radial lines originating from the wire
  4. (D) The field consists of concentric circles centred on the wire
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Correct answer: (D) The field consists of concentric circles centred on the wire

(d) — concentric circles centred on the wire.

37NCERT exercise · Q21 mark

At the time of short circuit, the current in the circuit

  1. (A) reduces substantially
  2. (B) does not change
  3. (C) increases heavily
  4. (D) varies continuously
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Correct answer: (C) increases heavily

(c) — resistance nearly zero, current very high.

38Board-style (practice)1 mark

The field near a long straight current-carrying wire is —

  1. (A) Straight lines parallel to the wire
  2. (B) Concentric circles
  3. (C) Radial lines
  4. (D) Only one straight line
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Correct answer: (B) Concentric circles

The field is concentric circles.

39Board-style (practice)1 mark

At a short circuit the current —

  1. (A) Falls heavily
  2. (B) Does not change
  3. (C) Rises heavily
  4. (D) Only changes slowly
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Correct answer: (C) Rises heavily

The current rises suddenly and heavily.

40Board-style (practice)1 mark

In the right-hand thumb rule the fingers show —

  1. (A) Current
  2. (B) The field
  3. (C) The force
  4. (D) The frequency
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Correct answer: (B) The field

The fingers curl along the field lines.

41Board-style (practice)1 mark

Inside a long solenoid the field —

  1. (A) Is zero
  2. (B) Is the same at every point
  3. (C) Always decreases
  4. (D) Crosses itself
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Correct answer: (B) Is the same at every point

The field inside is uniform.

42Board-style (practice)1 mark

In Fleming left hand the forefinger shows —

  1. (A) Force
  2. (B) Induced current
  3. (C) Magnetic field
  4. (D) Frequency
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Correct answer: (C) Magnetic field

The forefinger shows the magnetic field.

43Board-style (practice)1 mark

The colour of the earth wire is —

  1. (A) Red
  2. (B) Black
  3. (C) Green
  4. (D) Yellow only
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Correct answer: (C) Green

Green is earth.

44Board-style (practice)1 mark

The frequency of the home supply is —

  1. (A) 5 Hz
  2. (B) 50 Hz
  3. (C) 220 Hz
  4. (D) 15 Hz
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Correct answer: (B) 50 Hz

The frequency is 50 Hz.

45Board-style (practice)1 mark

The fuse wire melts because of —

  1. (A) Joule heating
  2. (B) Magnetic force alone
  3. (C) Induction
  4. (D) The compass
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Correct answer: (A) Joule heating

Joule heating melts the fuse when the current is too large.

46Board-style (practice)1 mark

Two field lines —

  1. (A) Always cross
  2. (B) Do not cross
  3. (C) Cross only inside
  4. (D) Cross only in AC
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Correct answer: (B) Do not cross

Two lines do not cross.

47Board-style (practice)1 mark

The force is maximum when current and field are —

  1. (A) Parallel
  2. (B) Perpendicular
  3. (C) Zero
  4. (D) In the same wire
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Correct answer: (B) Perpendicular

The force is largest in the perpendicular case.

48Board-style (practice)1 mark

The core of an electromagnet is usually —

  1. (A) Wood
  2. (B) Soft iron
  3. (C) Plastic
  4. (D) Dry paper
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Correct answer: (B) Soft iron

Soft iron becomes the core of an electromagnet.

49Board-style (practice)1 mark

How are appliances connected between live and neutral?

  1. (A) Only in series
  2. (B) In parallel
  3. (C) With no switch
  4. (D) Only to the earth wire
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Correct answer: (B) In parallel

Appliances are connected in parallel.

50Board-style (practice)1 mark

The field of a current coming out of the page is —

  1. (A) Anticlockwise
  2. (B) Always zero
  3. (C) A crossing of lines
  4. (D) Only a straight line
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Correct answer: (A) Anticlockwise

A current out of the page has an anticlockwise field.

51Board-style (practice)1 mark

The 15 A circuit is for which appliances?

  1. (A) Only a torch cell
  2. (B) Heavy appliances such as a geyser and a cooler
  3. (C) Only the compass
  4. (D) Only iron filings
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Correct answer: (B) Heavy appliances such as a geyser and a cooler

Heavy appliances go on the 15 A circuit.

52Board-style (practice)1 mark

The field lines around a straight current-carrying wire are —

  1. (A) Straight and parallel to the wire
  2. (B) Circles with the wire as centre
  3. (C) Only from north to south
  4. (D) Neither inside nor outside the wire
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Correct answer: (B) Circles with the wire as centre

The field lines are circles centred on the wire. The direction comes from the thumb rule.

53Board-style (practice)1 mark

Fleming’s left-hand rule gives —

  1. (A) The direction of the induced current
  2. (B) The direction of the force on a current-carrying wire
  3. (C) The rating of a fuse
  4. (D) Only the earth’s field
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Correct answer: (B) The direction of the force on a current-carrying wire

The left hand gives the force. The right hand gives the induced current.

54BSEB model · practice (not an annual paper)1 mark

Which of the following gives the direction of an induced current?

  1. (A) Fleming left hand
  2. (B) Fleming right hand
  3. (C) Only Joule heating
  4. (D) Only a parallel connection
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Correct answer: (B) Fleming right hand

Fleming right hand gives the induced current.

55BSEB model · practice (not an annual paper)1 mark

One cause of overloading is —

  1. (A) Too many appliances on one socket
  2. (B) Fitting a green wire
  3. (C) Keeping a compass
  4. (D) Sprinkling iron filings
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Correct answer: (A) Too many appliances on one socket

Too many appliances on one socket can overload it.

56BSEB model · practice (not an annual paper)1 mark

To make an electromagnet the wire is wound as —

  1. (A) A straight rod, with no turns
  2. (B) A solenoid on a soft-iron core
  3. (C) Only an open sheet of copper
  4. (D) A glass rod
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Correct answer: (B) A solenoid on a soft-iron core

Wire wound on a soft-iron core makes an electromagnet. The magnetism nearly goes when the current stops.

57Competency-based (not a PYQ)1 mark

A student runs a 2 kW oven on a 220 V, 5 A circuit. The most likely result is —

  1. (A) The current stays about 0.9 A and nothing happens
  2. (B) The current will be about 9.1 A and the fuse will melt
  3. (C) The current will be 220 A
  4. (D) The oven will become DC
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Correct answer: (B) The current will be about 9.1 A and the fuse will melt

I = 2000/220 ≈ 9.1 A, which is above 5 A, so the fuse melts.

58Competency-based (not a PYQ)1 mark

A loop on a table has a current that is anticlockwise as seen from above. The field inside the loop is —

  1. (A) Downward
  2. (B) Upward
  3. (C) Zero
  4. (D) Crossing, parallel to the table
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Correct answer: (B) Upward

For an anticlockwise current the field inside is upward. For clockwise it is downward.

← Chapter 12: Magnetic Effects of Electric Current — full notes, video, questions