Magnetic Effect of a Current Quiz
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5 questions, one answer each
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1. What causes a magnetic field to appear around a wire?
- A. The wire being made of a magnetic material
- B. An electric current flowing through the wire
- C. The wire being placed near a permanent magnet
- D. The wire being heated
2. What shape does the magnetic field take around a long straight current-carrying wire?
- A. Straight lines parallel to the wire
- B. Concentric circles around the wire
- C. A pattern identical to a bar magnet
- D. No consistent pattern
3. A student reverses the direction of current flow in a solenoid. What happens to the magnetic field?
- A. It disappears completely
- B. Its strength doubles
- C. Its direction reverses
- D. Nothing changes
4. A technician wants to use a low-power switch to safely control a high-current motor circuit. Which device, based on the magnetic effect of a current, should they use, and how does it work?
- A. A loudspeaker, because it can convert current to motion
- B. A relay, because a small current in its coil creates a magnetic field that closes contacts in a separate higher-current circuit
- C. A solenoid alone, because it always increases current automatically
- D. A capacitor, because it stores charge to boost the current
5. Two identical straight wires each carry a current, but wire A carries twice the current of wire B. A plotting compass is placed the same distance from each wire. Compare the deflection of the compass near each wire, and explain the underlying factor.
- A. The compass near wire B deflects more, because lower current always produces a stronger field
- B. The compass near wire A deflects more, because a larger current produces a stronger magnetic field at a given distance
- C. Both compasses deflect equally, because current size does not affect field strength
- D. Neither compass deflects, because a single wire cannot produce a detectable field