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Difficulty: HardElectromagnetism and Induction

When the direct current flowing through an inductor decreases, the self-induced electromotive force (counter-EMF) acts in the same direction as the original current to oppose the reduction in current flow.

Answer: Answer

Answer

True
The statement is true because Lenz's law dictates that self-induced voltage opposes the change in current rather than the absolute direction of current flow. When circuit current decreases, the collapsing magnetic field induces a voltage of such polarity that it acts in the same direction as the original current to sustain the flow.

Step-by-Step Solution

1
Analyze the fundamental principle of electromagnetic induction and Lenz's law for inductors.
Lenz's law states that the polarity of an induced electromotive force (EMF) always opposes the specific change in magnetic flux or current that creates it (e=−LΔIΔte = -L \frac{\Delta I}{\Delta t}).
Inductors store energy within their magnetic field and oppose instantaneous changes in current magnitude.
2
Evaluate the behavior of the magnetic field when current decreases.
As current decreases, the magnetic field around the inductor collapses across the coil windings, inducing an electromotive force.
A changing magnetic flux through a conductor induces an electric potential.
3
Determine the direction and polarity of the induced EMF relative to the original current.
To oppose the reduction in current (ΔI/Δt<0\Delta I / \Delta t < 0), the induced EMF acts as an aiding voltage source in the same direction as the original current flow.
Opposing a decay in current requires supplying voltage to keep current moving in the original direction.
4
Conclude the truth value of the statement.
The statement correctly describes the directional behavior of self-induced counter-EMF during current decay, confirming the statement is True.
Counter-EMF opposes the direction of current only when current is increasing; during current decrease, it reinforces the original current direction.

Key Concept

Lenz's Law and Self-Induction in Inductors
Estimated Time:45s
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Topics

Electromagnetism and Induction

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