3.3 - Electrical Terminology

Question 1

What is the unit of potential difference?

Answer 1

volt

Question 2

What is the unit of Electromotive Force (EMF)?

Answer 2

volt

Question 3

What are the main sources of EMF?

Answer 3

1. When electrodes of dissimilar materials are immersed in an electrolyte, as in primary and secondary cells
2. The relative movement of a conductor and a magnetic flux such as electric generators and transformers
3. The difference of temperature between junctions of dissimilar metals, as in thermocouples

Question 4

What is voltage?

Answer 4

Voltage is the pressure from an electrical circuit’s power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light or driving an electric motor.

Voltage is the measure of EMF or Potential Difference.

Question 5

What is one volt is equivalent to?

Answer 5

One volt is the magnitude of EMF that will cause one unit of energy to move one coulomb of charge from one point to another.

Question 6

If a potential difference exists between two bodies a current will flow when they are joined by a _______

While that current is flowing _____ energy is being generated

Answer 6

Conductor

Heat

Question 7

What is the unit of power

Answer 7

Watt

Question 8

What is one coulomb equal to?

Answer 8

6.28 x 10 ^18

Question 9

Does the size of an electrical current depend on the:

(a) rate of flow of electrons
(b) number of electrons

How can the equation be written?

Answer 9

(a)

The size of an electrical current is dependent on the rate of flow of electrons.

Question 10

What is current measured in and what is it equivalent to in coulombs?

Answer 10

Current is measured in Amperes

1 Ampere = 1 coulomb / second

Question 11

What is the most important factor in determining the resistance of a material and what are the other factors?

Answer 11

Resistivity factors:

Material (copper, aluminium, silver, gold) = most important

Other factors:

Length

C.S.A

Temperature

Question 12

What is the formula for calculating resistance?

Answer 12

Question 13

What symbol is used to represent resistivity?

Answer 13

Question 14

Most materials an increase in temperature causes an ______ in resistance

This is referred to as

Answer 14

increase

Positive temperature coefficient

PTC - metals usually have this property

Question 15

Some substances, such as _____ have a negative temperature coefficient. This means that their resistance ______ as temperature increases

Answer 15

Carbon

decreases

Question 16

What is the mathematical formula for Conductance?

Answer 16

Conductance is the recripocal of resistance.

Question 17

Which way is the direction of conventional current flow?

Answer 17

Question 18

Which way is the direction of electron flow?

Answer 18