Question

Two similar circular loops carry equal currents in the same direction. On moving coils further apart, the electric current will

• A. increase in both
• B. decrease in both
• C. remain unchanged
• D. increase in one coil and decrease in second coil

Hint:

The flux through each coil is self plus mutual. Moving them apart reduces the mutual contribution, and Lenz's law then makes the currents rise.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
The flux through each coil is \(\Phi=LI+MI\), because the currents are in the same direction and the fluxes add.

Step 2: Effect of Separation
As the coils move apart, the mutual inductance \(M\) decreases, so the total flux through each coil decreases.

Step 3: Lenz's Law
The induced emf opposes the fall in flux by trying to increase the current in each coil.

Step 4: Compare the options
The current increases in both coils.

Final Answer:
The current increases in both coils. \[ \boxed{\text{(A) }\text{increase in both}} \]