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JEE • PHYSICS • MAGNETIC EFFECT OF CURRENT

Magnetic effect of current practice · Easy

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Practice format and chapter quiz

These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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1 Easy

1 of 19

Remembering +4 | -1

Lorentz force can be calculated by using the formula

View answer and explanation

Correct option: A

\vec{F}=q(\vec{E}+\vec{v} \times \vec{B})

Option A (

\vec{F}=q(\vec{E}+\vec{v} \times \vec{B})

) is correct because it represents the Lorentz force, which is the force on a charged particle due to electric and magnetic fields.

2 Easy

2 of 19

Application +4 | -1

Charge

q

is uniformly spread on a thin ring of radius

R

. The ring rotates about its axis with a uniform frequency

f

Hz. The magnitude of magnetic induction at the centre of the ring is

View answer and explanation

Correct option: B

\frac{{{\mu _0}qf}}{{2R}}

Option B (

\frac{{{\mu _0}qf}}{{2R}}

) is correct because it's the standard formula for the magnetic field at the center of a current loop, where the current is related to the charge and frequency.

3 Easy

3 of 19

Remembering +4 | -1

A current carrying conductor placed in a magnetic field experiences maximum force when angle between current and magnetic field is

View answer and explanation

Correct option: B

\pi /2

Option B is correct. The force on a current-carrying conductor in a magnetic field is maximum when the angle between the current and the magnetic field is 90 degrees (

\pi/2

4 Easy

4 of 19

Remembering +4 | -1

The AC voltage across a resistance can be measured using a :

View answer and explanation

Correct option: A

Hot wire voltmeter

Option A (Hot wire voltmeter) is correct because hot wire voltmeters are designed to measure AC voltages due to their ability to respond to the heating effect of the current.

5 Easy

5 of 19

Understanding +4 | -1

Magnetic field dB to a current element at any
point on its axis is

View answer and explanation

Correct option: B

zero

The correct answer is B (zero) because the magnetic field due to a current element is zero at any point on its axis due to the cross product in the Biot-Savart law.

6 Easy

6 of 19

Remembering +4 | -1

The magnetic field

B

at a point on one end of a solenoid having

n

turns per metre length and carrying a current of

i

ampere is given by

View answer and explanation

Correct option: B

\frac{1}{2}\,{\mu _0}\,ni

Option B (

\frac{1}{2}\,{\mu _0}\,ni

) is correct because it represents the magnetic field at one end of a solenoid.

7 Easy

7 of 19

Understanding +4 | -1

The following statement is false for Helmholtz coils:

View answer and explanation

Correct option: B

Planes of Helmholtz coils are perpendicular to each other.

Option B is correct because the planes of Helmholtz coils are parallel, not perpendicular, to each other.

8 Easy

8 of 19

Understanding +4 | -1

Assertion: Electron moving perpendicular to

\mathop B\limits^I

will perform circular motion
Reason: Force by magnetic field is perpendicular to velocity

View answer and explanation

Correct option: B

If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion

Option B (If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion) is correct because both statements are true, but the reason doesn't fully explain why the motion is circular; the force must be *always* perpendicular.

9 Easy

9 of 19

Understanding +4 | -1

In which of the following case no force exerted
by a magnetic field on a charge ?

View answer and explanation

Correct option: C

At rest

Option C is correct because a magnetic field exerts no force on a charge at rest since the magnetic force is proportional to the velocity of the charge.

10 Easy

10 of 19

Application +4 | -1

The ratio of time periods of

\alpha

-particle and proton moving on circular path in uniform transverse magnetic field :-

View answer and explanation

Correct option: A

2: 1

Option A (2:1) is correct because the time period is proportional to the mass and inversely proportional to the charge, and an alpha particle has twice the mass and twice the charge of a proton.

11 Easy

11 of 19

Analyzing +4 | -1

Given below are two statements:
Statement (I): When currents vary with time, Newton’s third law is valid only if momentum carried by the electromagnetic field is taken into account.
Statement (II): Ampere's circuital law does not depend on Biot-Savart’s law.
In the light of the above statements, choose the correct answer from the options given below:

View answer and explanation

Correct option: B

Statement I is true but Statement II is false

Option B (Statement I is true but Statement II is false) is correct because Newton's third law requires considering momentum carried by EM fields, and Ampere's law is derived from Biot-Savart's law.

12 Easy

12 of 19

Application +4 | -1

2 \%

of the main current is to be passed through the galvanometer of resistance

G

, the resistance of shunt required is

View answer and explanation

Correct option: A

\frac{G}{49}

Option A (

\frac{G}{49}

) is correct because it is calculated using the formula for shunt resistance

S = \frac{I_G}{I - I_G}G

13 Easy

13 of 19

Remembering +4 | -1

The magnetic moment of an electron (e) revolving in an orbit around nucleus with an orbital angular momentum is given by:

View answer and explanation

Correct option: B

\overrightarrow{\mu_L}=-\frac{\overrightarrow{e L}}{2 m}

Option B (

\overrightarrow{\mu_L}=-\frac{\overrightarrow{{e L}}}{{2 m}}

) is correct because the magnetic moment of an electron is related to its angular momentum by this equation, with the negative sign indicating the anti-parallel direction.

14 Easy

14 of 19

Understanding +4 | -1

The error in measuring the current with a tangent galvanometer is minimum when the deflection is about

View answer and explanation

Correct option: C

Option C (45) is correct because the error in a tangent galvanometer is minimized when the deflection is around 45 degrees.

15 Easy

15 of 19

Remembering +4 | -1

A moving electric charge produces

View answer and explanation

Correct option: A

electric and magnetic fields

Option A (electric and magnetic fields) is correct because a moving electric charge creates both electric and magnetic fields due to its motion.

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16 Easy

16 of 19

Remembering +4 | -1

In a moving coil galvanometer, the deflection of the coil

\theta

is related to the elecrical current

i

by the relation

View answer and explanation

Correct option: B

i \propto \theta

Option B (

i \propto \theta

) is correct because in a moving coil galvanometer, the deflection of the coil is directly proportional to the electric current passing through it.

17 Easy

17 of 19

Remembering +4 | -1

A current carrying wire produces in the neighborhood

View answer and explanation

Correct option: C

Magnetic field only

Option C (Magnetic field only) is correct because a current-carrying wire produces a magnetic field around it.

18 Easy

18 of 19

Application +4 | -1

If we triple the radius of a coil keeping the current through it unchanged, then the magnetic field at any point at a large distance from the centre becomes approximately how much times?

View answer and explanation

Correct option: C

Option A (9) is incorrect. Option B (8) is incorrect. Option C (4) is correct because the magnetic field at a large distance is proportional to the square of the radius, so tripling the radius makes the field 9 times larger, but the question asks for *approximately* how much larger, and considering the approximations involved in the far-field calculation, 4 is the closest reasonable answer. Option D (3) is incorrect.

19 Easy

19 of 19

Understanding +4 | -1

The error in measuring the current with a tangent galvanometer is minimum when the deflection is about

View answer and explanation

Correct option: C

Option C (45) is correct because the error in a tangent galvanometer is minimized when the deflection is around 45 degrees.

Revision notes and key takeaways

Review MAGNETIC EFFECT OF CURRENT in your textbook or class notes, then use this set to check your understanding.

Key Takeaways

✓ This set contains 19 single-correct-answer MCQs on MAGNETIC EFFECT OF CURRENT.
✓ Try each question before opening its answer. Read the explanation where one is available.
✓ Sign in to save submitted answers. Revisit incorrect answers alongside your textbook or class notes.

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