Electromotive Force And Potential Difference

Question 1

Potential difference

Answer 1

The potential difference (p.d.) (aka voltage) between two points in a circuit is the energy lost by one coulomb as it moves from one point to the other.

• the unit of potential difference is the joule per coulomb (J C^-1) which is also called the volt (V)
• to measure potential difference we use a voltmeter

The potential difference between two points in a circuit is the amount of energy converted from electrical to other forms between the two points when 1 coulomb of charge passes any point of that circuit.

Question 2

Voltages in series

Answer 2

The potential difference across two (or more) consecutive parts of a series circuit is equal to the sum of the potential differences across each part

V = V1 + V2 + V3

Question 3

Voltages in parallel

Answer 3

The potential difference across each of a number of conductors connected in parallel with each other is the same

p.d across path 1 = p.d across path 2 = p.d across path 3

V1 = V2 = V3

Question 4

Voltemeter

Answer 4

• to measure potential difference we use a voltmeter

A voltmeter is always connected in parallel with the part of the circuit across which the p.d. is to be measured

Question 5

Electromotive force (emf)

Answer 5

A voltage when applied to a circuit is called an emf

• the symbol for emf is E
• its unit is obviously the volt

Question 6

Some sources of electromotive force (emf)

Answer 6

• electric cells
• a simple cell
• primary and secondary cells
• the thermocouple
• the mains

Question 7

Battery

Answer 7

A number of cells connected in series

Question 8

Primary cell

Answer 8

A cell that cannot be recharged

Question 9

Secondary cell

Answer 9

A cell that can be recharged

Also called an accumulator

Question 10

Mains electricity

Answer 10

The electricity supplied to your home