Question

electric motors convert electrical energy to mechanical energy. when the current - carrying coil is placed between the magnetic poles, a force acts on it that causes it to rotate. the image below shows a simple electric motor.
the motor is used to lift metal boxes. how can the motor be changed to be able to lift a heavier box?
a. decrease the size of the magnets
b. change the polarity of the magnet
c. add more loops of wire between the magnets
d. rotate the coil in a counter - clockwise direction

Explanation:

To lift a heavier box, the motor needs more force. The force on a current - carrying coil in a magnetic field is related to the number of wire loops (more loops mean more force as each loop contributes to the force). Option A: Decreasing magnet size reduces the magnetic field, so force decreases. Option B: Changing magnet polarity only changes the direction of force, not its magnitude. Option D: Changing the rotation direction (clockwise to counter - clockwise) doesn't change the force's ability to lift a heavier load, just the rotation direction. So adding more wire loops (Option C) increases the force, allowing lifting a heavier box.

Answer:

C. add more loops of wire between the magnets