Question

If a rectangular loop carrying a current I and area ab is placed such that a uniform magnetic field B is in the plane of the loop, then the magnitude of torque on it is

• A. \(I B a b\)
• B. \(I B a b / 2\)
• C. \(I B\)
• D. \(I B / 2\)
• E. \(2 I B a b\)

Hint:

Maximum torque occurs when plane of loop is parallel to magnetic field.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Torque on a current loop: \(\tau = I A B \sin \theta\), where \(\theta\) is angle between \(B\) and normal to plane.

Step 2: Detailed Explanation:
If \(B\) is in the plane of the loop, normal is perpendicular to \(B\), so \(\theta = 90^{\circ}\), \(\sin 90^{\circ} = 1\).
\(\tau = I (ab) B \cdot 1 = I B a b\)

Step 3: Final Answer:
Torque = \(I B a b\).