Physics for IGCSE & O level - Magnets And Currents (Section 12)

• 1

  Which device uses an electromagnet to open and close a circuit?

  回答

  (B)

  A relay
• 2

  In a step-down transformer, the number of turns in the primary coil is:

  回答

  (B)

  More than the secondary coil.
• 3

  The equation that relates voltage, current, and power is:

  回答

  (A)

  P = VI
• 4

  How is the strength of an electromagnet increased?

  回答

  A

  B

  C
• 5

  How does a relay work?

  回答

  (A)

  By using a small current to control a much larger current.
• 6

  What is the term for a coil of wire that is free to rotate in a magnetic field in an electric motor?

  回答

  (B)

  Armature
• 7

  Which of the following is a component of a simple electric motor?

  回答

  (B)

  An electromagnet