Question

A conducting loop is pulled with a constant velocity towards a region of constant (steady) magnetic field of induction B as shown in the figure. Then the current involved in the loop is (d > r)

• A. Clockwise
• B. Anti-clockwise
• C. Zero
• D. All of these

Answer 1

Answer: (D)

All of these

Answer 2

When the loop is drawn into the magnetic field, the area of the portion of the loop in the magnetic field will increase. That means, the flux linkage increases. Therefore an (anticlockwise) emf is induced in the loop so as to oppose the change, that is to say to oppose the increase in magnetic flux in the loop. Therefore, the current will have to induce in anti-clockwise direction to induce an opposing magnetic field, that is pointing outward of the page. After the complete enter of the loop into the magnetic field, no variation of flux occurs. Therefore it induces no current so long as the loop is completely inside the magnetic field. When it emerges out of the magnetic field, following the previous argument, the direction of induced in it will be eversed (clockwise). Hence (4) is correct.