Deck 14: Magnetic Induction

Question 1

If current is flowing in a circuit containing an inductor and the power switch is opened, the magnetic field surrounding the inductor collapses and induces voltage into the inductor, resulting in a voltage spike.

Answer 1

True

Question 2

Inductors always _______________ a change of current.

Answer 2

oppose

Question 3

What is one device used for spike suppression in either direct or alternating current circuits?

A) metal oxide varistor
B) voltage varistor
C) inductive varistor
D) capacitive varistor

Answer 3

A

Question 4

​Exponential curves are always divided into _____ time constants.

A) ​three
B) ​four
C) ​five
D) ​six

Question 5

If a conductor is moved upward, the polarity of induced voltage is reversed and the current flows in the _______________ direction.

Question 6

When a closed loop of wire cuts through magnetic flux lines, a current is induced into the loop. The current in the loop sets up a magnetic field that is in opposition to the original magnetic flux. This is essentially _____.

A) Coulomb's law
B) Ohm's law
C) Lenz's law
D) Weber's law

Question 7

The magnetic quantity Weber (Wb) is equal to 100,000,000 lines of flux. If a conductor cuts through one Weber per second, then a voltage of _____ volt(s) is induced into the conductor.

A) one
B) four
C) five
D) ten

Question 8

What is the unit of measurement for inductance?

A) farad (F)
B) henry (H)
C) ohm ( Ω )
D) Weber (Wb)

Question 9

When using the left-hand generator rule, the thumb points to the direction of _____.

A) flux
B) thrust
C) current
D) power

Question 10

A coil has an inductance of 3 H and a wire resistance of 15 Ω . How long will it take for the current to reach its full value?

A) 45 seconds
B) 0.2 seconds
C) 1.0 seconds
D) 25 seconds

Question 11

The time required for current in an inductor to reach its full Ohm's law value is called the _____ time constant.

A) R-L
B) R²
C) R-C
D) L-R

Question 12

An induced voltage opposes the motion that causes it according to _____.

A) Ohm's law
B) Lenz's law
C) Coulomb's theory
D) Fleming's rule

Question 13

When using the left-hand generator rule, the center finger points to the direction of _____.

A) thrust
B) flux
C) current
D) power

Question 14

The direction of induced current can be determined by using _____'s left-hand generator rule.

A) Ohm
B) Kirchhoff
C) Fleming
D) Coulomb

Question 15

During the period of time known as the first time constant of an exponential curve, the current will rise to about _____ percent of its full value.

A) 50
B) 31.8
C) 100
D) 63.2

Question 16

A way of determining the relationships of the motion of the conductor, the magnetic field direction, and the direction of the induced current is by using the _____.

A) left-hand generator rule
B) right-hand generator rule
C) left-hand motor rule
D) right-hand motor rule

Question 17

The amount of voltage induced into a conductor depends on the turns of wire, the strength of the magnetic field, and the speed of cutting action.

Question 18

When a conductor cuts magnetic lines of force, a voltage is induced into the conductor. This principle is called _____.

A) electromagnetic inductance
B) electric induction
C) magnetic inductance
D) electromagnetic induction

Question 19

If a voltage is being induced into a conductor by electromagnetic induction, reversing the direction of motion of the conductor will _____.

A) not change anything
B) reverse the polarity of the induced voltage
C) double the induced voltage
D) halve the induced voltage

Question 20

Losses in the core of iron core inductors include _____ and _____ losses.

A) eddy current; hysteresis
B) resistive; inductive
C) reactive; inductive
D) hysteresis; inductive

Question 21

When the current flow through an inductor stops and the current also decreases at an exponential rate, a (n) _______________ occurs.