Theory

Question 1

The current flowing in an ac circuit is affected by what three circuit properties?

Answer 1

Resistance
Inductance
Capacitance

Question 2

What makes up iron losses in an ac circuit?

Answer 2

Eddy currents - circulating currents built up in core due to changing magnetic field… Reduced with laminations

Hysteresis - energy lost due to magnetic friction in the core. Silicon steel in the core reduces hysteresis losses.

Question 3

List three factors that affect the amount the voltage produced by a generator.

Answer 3

Flux density
Length of conductor
Speed ( angle)

Question 4

Describe skin effect

Answer 4

It reduces the effective area of a conductor.

Question 5

Molecular friction losses in a material due to the changing magnetic polarities is known as?

Answer 5

Hysteresis

Question 6

This is energy loss due to the distortion of electrons inside the insulation.

Answer 6

Dielectric losses

Question 7

What is impedence

Answer 7

The total opposition to current in an ac circuit

Question 8

What is capacitance?

Answer 8

The opposition to a change in voltage

Question 9

What is inductance?

Answer 9

The opposition to a change in current

Question 10

What is resistance

Answer 10

The opposition to current flow on a molecular level.

Question 11

What is the symbol for impedence and what is it measured in?

Answer 11

The symbol is Z and it is measured in ohms

Question 12

What is the symbol for capacitance and what is it measured in?

Answer 12

Xc and measured in ohms

Question 13

What is a capacitor?

Answer 13

2 conductive poles sandwiching a dielectric material

Question 14

The affect capacitance has on an ac circuit is known as

Answer 14

Capacitive reactance

Question 15

The affect inductance has on an ac circuit is known as.

Answer 15

Inductive reactance

Question 16

What is inductance?

What is its symbol and unit of measurement?

Answer 16

Inductance is opposition to a change in current.
The symbol is ( L )
It is measured in henries (H)

Question 17

Factors that affect inductance

Answer 17

# of turns
Permeability of core
Area of core
Length of the core
L = N^2pA/ length

Question 18

What is lenzs law

Answer 18

A changing magnetic field in a coil will induce a voltage (counter emf) that will cause a current to flow that opposes the current that created it.

Question 19

What are factors that affect counter emf?

Answer 19

Amount of inductance in a coil
The rate at which the current changes

Emf = change in current X Inductance
Change in time

Question 20

What Is faradays law?

Answer 20

The amount of induced emf is directly proportional to the rate at which the lines of force are cut.

Question 21

What is induction?

Answer 21

Move a wire through a magnetic field and a voltage will be induced across it.

Question 22

Describe an inductor

Answer 22

Insulated Wire wound around a core.

Question 23

What are two types of induction?

Answer 23

Mutual induction

Self-induction

Question 24

What is mutual induction?

Answer 24

The generation of an emf in one conductor or circuit by a change of flux around a separate conductor or circuit.

Question 25

What is self induction?

Answer 25

The generation of an emf in a conductor or circuit by a change of flux density around that conductor or circuit.

Question 26

What is the difference between induction and inductance?

Answer 26

Induction is the process by which a voltage is produced by the interaction of a conductor and a magnetic field. Induction is the physical property of a circuit that opposes change in current.

Question 27

What is permeability?

Answer 27

The ability of a magnetic material to support the formation of a magnetic field within it.

Question 28

In a purely resistive circuit, Current lags voltagr by 90

True or false

Answer 28

False
In a purely resistive circuit
Current and voltage are “in phase”

Question 29

What are the 3 main power formulas?

Answer 29

P= I x V
P= I^2 X ohms
P= V^2 / ohms