INDUCTANCE & INDUCTIVE REACTANCE (030201d)

Question 1

How does the counter EMF produced by the changing magnetic field interact with the original circuit characteristics?

Answer 1

It will tend to aid the original current

Question 2

When the armature of an AC operated relay pulls in, then the inductance of the operating coil would ______

Answer 2

Increase

Question 3

If a small core within a coil is replaced with a bigger core, the inductance of the coil would _____

Answer 3

Decrease

Question 4

What is the symbol used to represent inductance?

Answer 4

L

Question 5

Which law states that any induced current will produce a flux that will oppose any change in the original flux

Answer 5

Lenz’s law

Question 6

When using the left-hand rule to determine the polarity of the counter EMF in a coil, the thumb points in the direction of the ______ ______

Answer 6

Relative motion

Question 7

The process by which a voltage is produced by the interaction between a magnetic field, and a conductor is known as _______

Answer 7

Induction

Question 8

If the rate of change of current in a coil increases, then the magnitude of the induced EMF will ______

Answer 8

Increase

Question 9

How many time constants are needed to reach a steady value of current?

Answer 9

5

Question 10

True or false

Whenever a resistor is connected in parallel with a DC operated coil, the purpose of this resistor is to reduce the high induced voltage due to the collapsing magnetic field

Answer 10

True

Question 11

What percentage of the final current is one time constant?

Answer 11

63.2%

Question 12

If the core of an iron core coil is removed, then the inductive reactance of the coil would _____

Answer 12

Decrease

Question 13

Inductive reactants varies directly with _____

Answer 13

Frequency

Question 14

In a purely inductive AC circuit, the current will always _____ the voltage drop due to inductive reactance by 90°

Answer 14

Lag

Question 15

What is the phase relationship between applied voltage and current in a purely inductive AC circuit?

Answer 15

90°

Question 16

True or false

In an AC circuit containing a pure inductor, current will always lead voltage by 90°

Answer 16

False!!!

Current LAGS voltage in a purely inductive circuit

Question 17

What does the symbol Q represent?

Answer 17

Reactive power

Question 18

What is the unit of measurement for reactive power?

Answer 18

VARs

Volt-ampere reactive

Question 19

Decreasing the resistance of the wire used in a coil will ________ the phase angle

Answer 19

Increase

Question 20

If a certain size core is replaced with a smaller core, what happens to the inductance of the coil?

Answer 20

It decreases

Question 21

What symbol is used to represent the unit of measurement for inductance?

Answer 21

H

Question 22

Why is a resistor connected in parallel with a DC operated coil?

Answer 22

To reduce the high induced voltage due to the collapsing magnetic field

Question 23

If the core of an iron core coil is removed, then the inductive reactance of the coil would ______

Answer 23

Decrease

Question 24

When the armature of an AC operated relay pulls in, the inductive reactance of the coil will ______

Answer 24

Increase

Question 25

What is Faraday’s law?

Answer 25

The amount of EMF induced is directly proportional to the rate of change of flux

Question 26

Induced voltage is at ___ when the current it at max

Answer 26

0

Zero

Question 27

What is reactive power?

Answer 27

The rate the energy is stored and returned to the circuit

Vars

Question 28

What is the reactive power formula?

Answer 28

Q= Vx x Ix