Question

Induced EMF's are always in such a direction as to ______ the change that generated them

• A. oppose
• B. against
• C. favor
• D. unfavour

Hint:

Lenz's law: induced emf always opposes the change in magnetic flux that produces it.

Answer 1

The Correct Option is A

Concept:
This question is based on Lenz's law. Lenz's law states that the direction of induced emf or induced current is such that it opposes the change in magnetic flux that produced it. This law follows the principle of conservation of energy.

Step 1: Understand induced emf.
Induced emf is produced when there is a change in magnetic flux linked with a circuit. Magnetic flux can change due to: \[ \text{change in magnetic field} \] \[ \text{change in area} \] \[ \text{change in orientation} \] \[ \text{relative motion between magnet and coil} \]

Step 2: Apply Lenz's law.
According to Lenz's law, the induced emf never supports the change that produces it. Instead, it acts in a direction that opposes the cause of induction. So: \[ \text{Induced emf opposes the change producing it} \]

Step 3: Understand why it opposes.
If induced current favored the change, energy would be created continuously without external work. That would violate conservation of energy. So opposition is necessary.

Step 4: Check the options.
Option (A) oppose is correct.
Option (B) against is grammatically similar but the standard word used in Lenz's law is oppose.
Option (C) favor is incorrect because induced emf does not support the change.
Option (D) unfavour is not the standard scientific term. Hence, the correct answer is: \[ \boxed{(A)\ \text{oppose}} \]