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Question:

A conducting loop in the shape of a right-angled isosceles triangle of height 10 cm is kept such that the 90° vertex is very close to an infinitely long conducting wire (see the figure). The wire is electrically insulated from the loop. The hypotenuse of the triangle is parallel to the wire. The current in the triangular loop is in the counter-clockwise direction and increased at a constant rate of 10 A/s. Which of the following statement(s) is (are) true?

There is a repulsive force between the wire and the loop

If the loop is rotated at a constant angular speed about the wire, an additional emf of (μ₀π) volt is induced in the wire

The induced current in the wire is in the opposite direction to the current along the hypotenuse

The magnitude of induced emf in the wire is (μ₀π) volt

Solution:

Coefficient of mutual inductance M = μ₀l₀π
emf = -MdI/dt = μ₀l₀π(10) = μ₀π volt
As per Lenz's law, the loop must move away. Hence there must be a repulsive force. Answer is option A and C.