Key Topic 2: Magnetism

Question 1

3-2A1: What determines the strength of the magnetic field around a conductor?

A. The resistance divided by the current.
B. The ratio of the current to the resistance.
C. The diameter of the conductor.
D. The amount of current.

Answer 1

D. The amount of current.

Question 2

3-2A2: What will produce a magnetic field?

A. A DC source not connected to a circuit.
B. The presence of a voltage across a capacitor.
C. A current flowing through a conductor.
D. The force that drives current through a resistor.

Answer 2

C. A current flowing through a conductor.

Question 3

3-2A3: When induced currents produce expanding magnetic fields around conductors in a direction that opposes the original magnetic field, this is known as:

A. Lenz’s law.
B. Gilbert’s law.
C. Maxwell’s law.
D. Norton’s law.

Answer 3

A. Lenz’s law.

Question 4

3-2A4: The opposition to the creation of magnetic lines of force in a magnetic circuit is known as:

A. Eddy currents.
B. Hysteresis.
C. Permeability.
D. Reluctance.

Answer 4

D. Reluctance.

Question 5

3-2A5: What is meant by the term “back EMF”?

A. A current equal to the applied EMF.
B. An opposing EMF equal to R times C (RC) percent of the applied EMF.
C. A voltage that opposes the applied EMF.
D. A current that opposes the applied EMF.

Answer 5

C. A voltage that opposes the applied EMF.

Question 6

3-2A6: Permeability is defined as:

A. The magnetic field created by a conductor wound on a laminated core and carrying current.

B. The ratio of magnetic flux density in a substance to the magnetizing force that produces it.

C. Polarized molecular alignment in a ferromagnetic material while under the influence of a magnetizing force.

D. None of these.

Answer 6

B. The ratio of magnetic flux density in a substance to the magnetizing force that produces it.