A uniform magnetic field of 2 x 10-3 T acts along positive Y-direction. A rectangular loop of sides 20 cm and 10 cm with current of 5 A is Y-Z plane. The current is in anticlockwise sense with reference to negative X axis. Magnitude and direction of the torque is :

The area vector A is perpendicular to the plane of the loop. According to the right-hand rule, an anticlockwise current observed from the negative X-axis means the area vector points in the negative X-direction. Area of the loop, A = 0.2 m x 0.1 m = 0.02 m2 Magnetic moment vector: The magnetic field is B = 2 x 10-3 j T. Torque on the loop: The -k direction corresponds to the negative Z-direction. Magnitude is 2 x 10-4 N-m. Identify the plane of the loop to get the possible normal vectors. Since the loop is in the Y-Z plane, A must be pmi. 'Anticlockwise from -X' fixes it as -i. Simply apply cross product -i x j = -k. Class 12 Physics: Moving Charges and Magnetism

A uniform magnetic field of 2 x 10-3 T acts along positive Y-direction. A rectangular loop of sides 20 cm and 10 cm with current of 5 A is Y-Z plane. The current is in anticlockwise sense with referen

The area vector A is perpendicular to the plane of the loop. According to the right-hand rule, an anticlockwise current observed from the negative X-axis means the area vector points in the negative X-direction. Area of the loop, A = 0.2 m x 0.1 m = 0.02 m2 Magnetic moment vector: The magnetic field is B = 2 x 10-3 j T. Torque on the loop: The -k direction corresponds to the negative Z-direction. Magnitude is 2 x 10-4 N-m. Identify the plane of the loop to get the possible normal vectors. Since

A uniform magnetic field of 2 x 10-3 T acts along positive Y-direction. A rectangular loop of sides 20 cm and 10 cm with current of 5 A is Y-Z plane. The current is in anticlockwise sense with reference to negative X axis. Magnitude and direction of the torque is :

The area vector A is perpendicular to the plane of the loop. According to the right-hand rule, an anticlockwise current observed from the negative X-axis means the area vector points in the negative X-direction. Area of the loop, A = 0.2 m x 0.1 m = 0.02 m2 Magnetic moment vector: The magnetic field is B = 2 x 10-3 j T. Torque on the loop: The -k direction corresponds to the negative Z-direction. Magnitude is 2 x 10-4 N-m. Identify the plane of the loop to get the possible normal vectors. Since the loop is in the Y-Z plane, A must be pmi. 'Anticlockwise from -X' fixes it as -i. Simply apply cross product -i x j = -k. Class 12 Physics: Moving Charges and Magnetism

A uniform magnetic field of 2 x 10-3 T acts along positive Y-direction. A rectangular loop of sides 20 cm and 10 cm with current of 5 A is Y-Z plane. The current is in anticlockwise sense with referen

The area vector A is perpendicular to the plane of the loop. According to the right-hand rule, an anticlockwise current observed from the negative X-axis means the area vector points in the negative X-direction. Area of the loop, A = 0.2 m x 0.1 m = 0.02 m2 Magnetic moment vector: The magnetic field is B = 2 x 10-3 j T. Torque on the loop: The -k direction corresponds to the negative Z-direction. Magnitude is 2 x 10-4 N-m. Identify the plane of the loop to get the possible normal vectors. Since

A uniform magnetic field of 2 x 10-3 T acts along positive Y-direction. A rectangular loop of sides 20 cm and 10 cm…

Year	2026	2025	2024	Total
Questions	9	18	15	42

Year

2026

2025

2024

Total

Questions

Solution & Explanation

Related Formula

M = i A

τ = M \times B

Core Logic

The area vector $A$ $\vec{A}$ is perpendicular to the plane of the loop. According to the right-hand rule, an anticlockwise current observed from the negative X-axis means the area vector points in the negative X-direction.

Torque on a Current Loop diagram for Q32 - JEE Main 2024 Evening

Step 1: Calculating Magnetic Moment

Area of the loop, $A = 0.2 m \times 0.1 m = 0.02 m²$

Magnetic moment vector:

M = i A

M = 5 \times (0.2) \times (0.1) (- i)

M = 0.1(- i) A m²

Step 2: Calculating Torque

The magnetic field is $B = 2 \times 10⁻³ j T$ .

Torque on the loop:

τ = M \times B

τ = 0.1(- i) \times (2 \times 10⁻³ j)

τ = 2 \times 10⁻⁴ (- k) N-m

Step 3: Final Direction

The $- k$ $-\hat{k}$ direction corresponds to the negative Z-direction. Magnitude is $2 \times 10⁻⁴ N-m$ $2 \times 10^{-4} \text{ N-m}$.

Pattern Recognition

Identify the plane of the loop to get the possible normal vectors. Since the loop is in the Y-Z plane, $A$ $\vec{A}$ must be $\pm i$ $\pm\hat{i}$. 'Anticlockwise from -X' fixes it as $- i$ $-\hat{i}$. Simply apply cross product $- i \times j = - k$ $-\hat{i} \times \hat{j} = -\hat{k}$.

Chapter Mix

Class 12 Physics: Moving Charges and Magnetism

More Moving Charges and Magnetism Previous-Year Questions — Page 9

Q jee_main_2024_31_jan_morning Magnetic Force On Wire

A rigid wire consists of a semicircular portion of radius

R

and two straight sections. The wire is partially immersed in a perpendicular magnetic field

B = B₀ j

as shown in figure. The magnetic force on the wire if it has a current

i

is:

Magnetic Force On Wire diagram for Q35 - JEE Main 2024 Morning — A U-shaped current wire is placed in a uniform magnetic field with outward field lines.

A. $-iBR j$ $-iBR \hat{j}$
B. $2iBR j$ $2iBR \hat{j}$
C. $iBR j$ $iBR \hat{j}$
D. $-2iBR j$ $-2iBR \hat{j}$