Question

What will happen, if an open circuit is used in place of the closed loop (in figure below $CD$ is open circuit)?

• A. emf is induced across the open ends with $C$ positive
• B. emf is not induced across the open ends of the circuit
• C. emf is induced across ends with $C$ negative
• D. emf is induced with both $C,D$ positive and mid-point negative

Answer 1

Answer: (A)

An emf is induced across the open ends of the circuit. The direction of the induced emf can be found using Lenz's law. For conductor $CD,C$ is at positive potential. We shall use lenz's law to find polarity.
When S-role of magnet goes away from coil it induces $N$-pole at $C$ and $S$-pole at $D$ so that movement of magnet is prevents.
Creation of $N$-pole at $C$ induces anti cloclewise current at $C$ or $+ve$ polarity at $C$. It $c$ and $c$ are foiled lay wire current will flow from $C$ to $D$ through the wire.

North polarity creats anti-clock wise current