Chapter 21, Problem 10Q

To determine

To Explain: The counter torque in generator opposes motion.

Explanation of Solution

Introduction:

In the upper armature segment, the induced current points into the page. The right-hand rule can be used to understand this. The charges in the top armature segment move in the direction of the velocity representedby the green arrow, and these charges move in a magnetic field represented by the blue arrows (to the right). As per right-hand rule, the charges experience a force into the page generating the induced current.

As per right-hand rule, a wire carrying current, the current moving into the page (as in the upper armature segment) in a magnetic field directed to the right, would experience a force in a downward direction. This force exerts a counter-clockwise torque on the armature when it rotates in a clockwise direction. The back emf opposesthe armature’s motionwhileit isin operation.