Quiz 2 Flashcards Preview

Electrical theory > Quiz 2 > Flashcards

Flashcards in Quiz 2 Deck (72)
Loading flashcards...
0

Important date to remember?

Hans Christian Oersted, 1819

1

What is an electromagnet?

A non magnetic material that takes on the characteristics of a magnet whenever electrical current is passed through

2

Left hand rule?

Point the thumb in the direction of electron flow and the fingers will wrap in the orientation of flow

3

Why are the lines of flux of a single conductor not useful?

They have no polarity and are too weak to be useful.

4

What are the two ways flux strength can be increased?

Increasing the current through the conductor, increasing the density of the lines of flux.

5

Flux density can be increased in what two ways?

By wrapping conductor in a coil, inserting a highly permeable core

6

what are the advantages to forming a coil?

The strength of the flux is increased , and gives the flux polarity

7

Left hand rule for coils?

Wrap the fingers of the left hand around the coil in the direction of electron flow, the thumb will point to the North Pole

8

In what two ways can the polarity of a coil be reversed?

Reverse the current flow through the conductor, reverse the direction of the wraps.

9

Measurements of flux?

Gilbert and amp turn

10

What is the advantage to having an electromagnet?

It has the characteristics of a natural magnet which can be controlled, both strength and polarity

11

Uses for electromagnets?

Relays, solenoids, generators, alternators, motors

12

Difference between a relay and a solenoid?

Relay uses a non movable core

13

What is a relay/solenoid?

An electrical switch which is operated by an electromagnet

14

What is the purpose of a relay?

To use a small amount of current to control a large amount of current

15

What is a generator/alternator?

A device which uses an electromagnet to generate electricity

16

Difference between a generator and an alternator?

In a generator the electromagnet does not spin

17

What is a motor?

A device in which two electromagnets with fields that repel each other and cause one of them to spin

18

What are the sources of electricity?

Magnetism, chemical, heat, pressure, light.

19

Example of magnetic power?

Alternator, generator

20

Example of chemical power?

Batteries

21

Example of thermal power?

Thermocouples

22

Example of pressure power?

Record needle

23

Example of light power?

Solar panels

24

What is the definition of a complete circuit?

An electrical circuit where there is a complete path from the source, to the load, and back to the source.

25

What is a source?

The part of the circuit that provides the potential for electron transfer.

26

What is a conductor?

The path by which electrons flow from the source, to the load , and back to the source.

27

What is the major consideration for choosing a material for a conductor?

Weight versus resistance

28

What are factors effecting resistance?

Resistivity, positive temperature coefficient of resistance, dimension of the conductor.

29

What is the cross sectional area of a conductor given in?

Circular mils.