Force on a Current-Carrying Conductor Quiz
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5 questions, one answer each
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1. What is the motor effect?
- A. The attraction between two permanent magnets
- B. The force on a current-carrying conductor in a magnetic field
- C. The generation of a current by a moving magnet
- D. The heating effect of a current in a resistor
2. In an electric motor, what is the role of the split-ring commutator?
- A. It increases the strength of the magnetic field
- B. It reverses the current in the coil every half-turn so it keeps spinning one way
- C. It converts a.c. current into d.c. current for the whole circuit
- D. It measures the speed of rotation
3. A wire carrying a current is placed between magnetic poles and experiences an upward force. What happens to the force if only the direction of the current is reversed?
- A. The force stays upward
- B. The force becomes downward
- C. The force disappears entirely
- D. The force becomes sideways, perpendicular to both original directions
4. A student wants to increase the turning effect of a simple electric motor without changing the current or the magnet used. What could they do, and why does it work?
- A. Reduce the number of turns on the coil, because fewer turns spin faster
- B. Increase the number of turns on the coil, because more turns increase the total turning effect for the same current and field
- C. Remove the split-ring commutator, because it slows down rotation
- D. Replace the coil with a straight wire, because straight wires produce a stronger motor effect
5. A beam of negatively charged particles travels through a magnetic field and is observed to curve. Using the same underlying principle as the motor effect, explain why this curving occurs.
- A. The particles slow down due to friction with the field lines
- B. The moving charges constitute a current, and this current experiences a force perpendicular to both its velocity and the magnetic field, causing it to curve
- C. The magnetic field converts the particles' charge from negative to positive, reversing their path
- D. Charged particles are unaffected by magnetic fields unless they are stationary