This is the Multiple Choice Questions (MCQs) in Chapter 8: Magnetism from the book Teach Yourself Electricity and Electronics, 5th edition by Stan Gibilisco. If you are looking for a reviewer in Electronics Engineering this will definitely help you before taking the Board Exam.
Begin the Test
1. The geomagnetic field:
- A. Makes the earth like a huge horseshoe magnet.
- B. Runs exactly through the geographic poles.
- C. Is what makes a compass work.
- D. Is what makes an electromagnet work.
2. Geomagnetic lines of flux:
- A. Are horizontal at the geomagnetic equator.
- B. Are vertical at the geomagnetic equator.
- C. Are always slanted, no matter where you go.
- D. Are exactly symmetrical around the earth, even far out into space.
3. A material that can be permanently magnetized is generally said to be:
- A. Magnetic.
- B. Electromagnetic.
- C. Permanently magnetic.
- D. Ferromagnetic.
4. The force between a magnet and a piece of ferromagnetic metal that has not been magnetized:
- A. Can be either repulsive or attractive.
- B. Is never repulsive.
- C. Gets smaller as the magnet gets closer to the metal.
- D. Depends on the geomagnetic field.
5. Magnetic flux can always be attributed to:
- A. Ferromagnetic materials.
- B. Aligned atoms.
- C. Motion of charged particles.
- D. The geomagnetic field.
6. Lines of magnetic flux are said to originate:
- A. In atoms of ferromagnetic materials.
- B. At a north magnetic pole.
- C. Where the lines converge to a point.
- D. In charge carriers.
7. The magnetic flux around a straight, current-carrying wire:
- A. Gets stronger with increasing distance from the wire.
- B. Is strongest near the wire.
- C. Does not vary in strength with distance from the wire.
- D. Consists of straight lines parallel to the wire.
8. The gauss is a unit of:
- A. Overall magnetic field strength.
- B. Ampere-turns.
- C. Magnetic flux density.
- D. Magnetic power.
9. A unit of overall magnetic field quantity is the:
- A. Maxwell.
- B. Gauss.
- C. Tesla.
- D. Ampere-turn.
10. If a wire coil has 10 turns and carries 500 mA of current, what is the magnetomotive force in ampere-turns?
- A. 5000.
- B. 50.
- C. 5.0.
- D. 0.02.
11. If a wire coil has 100 turns and carries 1.30 A of current, what is the magnetomotive force in gilberts?
- A. 130.
- B. 76.9.
- C. 164.
- D. 61.0.
12. Which of the following is not generally possible in a geomagnetic storm?
- A. Charged particles streaming out from the sun.
- B. Fluctuations in the earth’s magnetic field.
- C. Disruption of electrical power transmission.
- D. Disruption of microwave radio links.
13. An ac electromagnet:
- A. Will attract only other magnetized objects.
- B. Will attract pure, unmagnetized iron.
- C. Will repel other magnetized objects.
- D. Will either attract or repel permanent magnets, depending on the polarity.
14. An advantage of an electromagnet over a permanent magnet is that:
- A. An electromagnet can be switched on and off.
- B. An electromagnet does not have specific polarity.
- C. An electromagnet requires no power source.
- D. Permanent magnets must always be cylindrical.
15. A substance with high retentivity is best suited for making:
- A. An ac electromagnet.
- B. A dc electromagnet.
- C. An electrostatic shield.
- D. A permanent magnet.
16. A relay is connected into a circuit so that a device gets a signal only when the relay coil carries current. The relay is probably:
- A. An ac relay.
- B. A dc relay.
- C. Normally closed.
- D. Normally open.
17. A device that reverses magnetic field polarity to keep a dc motor rotating is:
- A. A solenoid.
- B. An armature coil.
- C. A commutator.
- D. A field coil.
18. A high tape-recorder motor speed is generally used for:
- A. Voices.
- B. Video.
- C. Digital data.
- D. All of the above.
19. An advantage of a magnetic disk, as compared with magnetic tape, for data storage and retrieval is that:
- A. A disk lasts longer.
- B. Data can be stored and retrieved more quickly with disks than with tapes.
- C. Disks look better.
- D. Disks are less susceptible to magnetic fields.
20. A bubble memory is best suited for:
- A. A large computer.
- B. A home video entertainment system.
- C. A portable cassette player.
- D. A magnetic disk.