8.05 Potential difference

Question 1

What is the scientific name for voltage?

Answer 1

The scientific name for voltage is potential difference (p.d.)

Question 2

How can p.d. be measured?

Answer 2

P.d. can be measured using a voltmeter across the terminals of the cell.

Question 3

What is the SI unit of p.d.?

Answer 3

The SI unit of p.d. is the volt (V).

Question 4

What are volts in terms of joules and coulombs?

Answer 4

If the p.d. across a cell is 1 volt, then 1 joule of potential energy is given to each coulomb of charge. In other words, 1 volt means 1 joule per coulomb.

Question 5

What is e.m.f.?

Answer 5

A cell produces its highest p.d. when not in circuit and not supplying current. This maximum p.d. is called electromotive force (e.m.f.) of the cell. When the current is being supplied, the p.d. drops because of energy wastage inside the cell.

Question 6

Cells in series

Answer 6

To produce a higher p.d., several cells can be connected in series (in line).

Question 7

What does battery mean?

Answer 7

The word battery means a collection of joined cells, although it is commonly used for a single cell as well.

Question 8

P.d.s around a circuit

Answer 8

Moving around a circuit, from one battery terminal to the other, the sum of the p.d.s across the components is equal to the p.d. across the battery.

Question 9

Definition of electromotive force.

Answer 9

The e.m.f. of a cell or other source is work done per unit of charge by the cell in driving charge round a complete circuit.

Question 10

P.d. definition

Answer 10

The potential difference across a component is the work done per unit of charge in driving the charge through the component.

Question 11

Current

Answer 11

Current is measured in amperes using an ammeter. If 1 ampere flows for 1 second, the charge passing is 1 C.