Lenz’s law in action: When the current in a coil is interrupted and its magnetic field collapses, what is the direction of the induced current relative to the original current?

Introduction / Context:
Lenz’s law governs the polarity of induced emf in inductors and transformers. Understanding the direction of induced current during switching events is vital for selecting snubbers, flyback diodes, and protection components in power electronics and relay/solenoid driving circuits.

Given Data / Assumptions:

• A coil (inductor) carries current that is suddenly reduced or interrupted.
• The magnetic field stored around the inductor collapses.
• No specific circuit is given, but the polarity/direction question is general.

Concept / Approach:
Lenz’s law states that the induced emf always acts to oppose the change in current that produced it. When the source current is removed, the inductor “tries” to keep current flowing in the same direction. Hence the induced current will continue in the original direction for as long as energy remains in the magnetic field, frequently producing a large voltage spike to maintain that current through any available path.

Step-by-Step Solution:
Initial condition: coil carries current I in a given direction.Source is opened → di/dt is negative (current is attempting to drop quickly).Induced emf polarity is such that it sustains current in the same direction to oppose the decrease.Therefore, induced current direction is the same as the original current direction.

Verification / Alternative check:
Observe diode-flyback behavior: with a diode placed across a coil (cathode to positive side), the current freewheels in the same direction through the diode path when the driving switch opens—experimental confirmation of Lenz’s law.

Why Other Options Are Wrong:
Go to zero: current decays but does not instantly drop to zero; the inductor resists instantaneous change.Aid counter emf buildup (without direction): incomplete; the crucial point is the same-direction current to oppose the change.Opposite direction: would accelerate the change rather than oppose it, violating Lenz’s law.

Common Pitfalls:
Confusing steady-state current direction with induced current polarity during transient events. Remember, inductors resist change in current, not current itself.

Final Answer:
be in the same direction