According to Lenz’s law, as a magnetic field collapses in a coil, what is the polarity of the induced voltage relative to the original cause (the force creating the field)?

Introduction / Context:
Lenz’s law is the sign convention of electromagnetic induction. It dictates how induced voltages and currents oppose the changes that produced them. This principle explains flyback voltages, back-EMF in motors, and the self-protective behavior of inductors.

Given Data / Assumptions:

• A magnetic field linked to a coil is collapsing (flux decreasing).
• The original “force” is the cause of the field (source current or magnetizing action).
• We are considering the polarity of the induced voltage.

Concept / Approach:
Faraday’s law says induced EMF is proportional to the negative rate of change of flux linkage. Lenz’s law interprets the negative sign: the induced voltage drives a current whose magnetic field opposes the change in original flux. During collapse, the induced voltage polarity acts to keep current flowing in the same direction, thereby opposing the decrease in flux.

Step-by-Step Solution:
Original field decreases → coil responds with induced EMF.By Lenz’s law, this EMF produces a magnetic effect opposing the decrease.Therefore, the induced voltage polarity is opposite to the cause that created the field.Practically, this appears as a “kick” of opposite polarity when current is interrupted.

Verification / Alternative check:
Observe a relay coil without a flyback diode: interrupting current produces a high-voltage spike of opposite polarity across the coil, consistent with opposition to the change.

Why Other Options Are Wrong:
Independence or randomness contradicts Faraday–Lenz law.

“Identical” would reinforce the change, violating energy conservation.

“Only if stationary” is irrelevant; induction arises from changing flux.

Common Pitfalls:
Confusing “opposes the change” with “opposes the original quantity.” The induced effect tries to keep flux from changing, not always to cancel the original field steady value.

Final Answer:
opposite to the force creating it