NCERT Class 10 Science — Chapter 4: Magnetic Effects of Electric Current

mcqmedium

Assertion (A): The magnetic field is stronger near the poles of a magnet. Reason (R): The magnetic field lines are widely spaced near the poles.

Official previous-year question

Verified 1 Aug 2026.

Options

ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is NOT the correct explanation of A
CA is true but R is false
DA is false but R is true

Did you get this right?

Solution

The correct option is

A is true but R is false

Explanation

The relative strength of a magnetic field is represented by the degree of closeness of the magnetic field lines. The density of these lines is directly proportional to the intensity of the magnetic field in that region.

Assertion (A) is Correct: The magnetic field is indeed strongest near the poles of a magnet. This is the region where the magnetic force exerted on magnetic materials is maximum.
Reason (R) is Incorrect: Magnetic field lines are crowded (closely packed) near the poles, not widely spaced. The crowding of field lines indicates a strong magnetic field. Conversely, widely spaced field lines represent a weak magnetic field. Therefore, the statement that lines are widely spaced near the poles contradicts the property of a strong magnetic field.

Key Takeaway: Magnetic field lines are densest where the magnetic field is strongest (at the poles) and sparse where the field is weak.

Your note

More from Chapter 4: Magnetic Effects of Electric Current

With reference to magnetic field lines, consider the following statements: 1. Outside a magnet, they are taken to originate from the north pole and terminate at the south pole. 2. Inside a magnet, they run from the south pole to the north pole. 3. The closeness of lines is independent of the relative strength of the field. 4. Two magnetic field lines can intersect at a point. Which of the statements given above is/are correct?

medium

Assertion (A): Magnetic field is a vector quantity. Reason (R): Magnetic field lines are closer together where the magnetic field is strong.

hard

Which of the following changes will increase the displacement of a current-carrying rod in a uniform magnetic field? 1. Increasing the current reduces the displacement of the rod. 2. Using a stronger magnet. 3. Increasing the effective length within the field has no effect on displacement. Which of the statements given above is/are correct?

medium

Which medical imaging technique relies on strong magnetic fields and radio waves?

easy

Assertion (A): The metallic body of an electric appliance is connected to the earth wire. Reason (R): The earth wire provides a high resistance path for the current.

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Keep practising Chapter 4: Magnetic Effects of Electric Current

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The correct option is

A is true but R is false

Explanation

Assertion (A) is Correct: The magnetic field is indeed strongest near the poles of a magnet. This is the region where the magnetic force exerted on magnetic materials is maximum.
Reason (R) is Incorrect: Magnetic field lines are crowded (closely packed) near the poles, not widely spaced. The crowding of field lines indicates a strong magnetic field. Conversely, widely spaced field lines represent a weak magnetic field. Therefore, the statement that lines are widely spaced near the poles contradicts the property of a strong magnetic field.

Key Takeaway: Magnetic field lines are densest where the magnetic field is strongest (at the poles) and sparse where the field is weak.