- #1
blooperkin
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Homework Statement
The armature of a simple motor consists of a square coil and carries a current of 0.55 A just before it starts to move. The coil is positioned perpendicular to a magnetic field. Explain briefly why the current falls below 0.55A once the coil of the motor is rotating.
Homework Equations
Lenz' Law
Faraday's Law
The Attempt at a Solution
My answer: When the coil rotates, there is a rate of change of cutting of magnetic flux linking the coil, so by Faraday's Law, an induced emf and thus current is induced. By Lenz' Law, the current acts in a direction to oppose the change that is producing it, and thus flows in a direction opposite to the initial current, resulting in a net loss of current flowing in the original direction.
However, I wasn't awarded the mark as my teacher said the induced emf acts in an opposite direction, not the induced current. However, I'm confused as I've always thought current can flow in different directions. Is it because a current is a scalar quantity and emf is a vector quantity?