4.2.2 Current, 4.2.3 Electromotive Force, 4.2.4 Potential Difference

Question 1

Define Current and state its formula

Answer 1

The rate at which electrical charge passes a point in a circuit

I = Q/t
current = Quantity of Charge / t

Question 2

How does one measure current

Answer 2

An Ammeter is used to measure an electric current. There are two types of ammeters..
- Analogue: It has a needle that moves across a scale. Judgement has to be made for the position of the needle on the scale.
- Digital: Gives a direct read out in figures.
An Ammeter is connected to a circuit in series (in which the current flows in one direction, in positive terminal and out negative terminal).
If the meter is connected the wrong way round it will give negative readings.

Question 3

Unit of Current

Answer 3

Amps / Ampere

Question 3

What is conventional current

Answer 3

a flow of positive charge, moving from positive to negative.

Question 4

What is electron flow

Answer 4

A movement of conduction electrons from negative to positive.

Question 5

Define electromotive force

Answer 5

The energy supplied by the source in driving a unit charge around a circuit
The maximum voltage a cell can produce is called the electromotive force.
Electromotive force (e.m.f) is measured in volts.

Question 6

What is Potential Difference?

Answer 6

It is the work done per unit charge in moving between two points in a circuit.

Formula: 1V = 1J/C

Question 7

How is voltage measured?

Answer 7

Voltage is measured by a voltmeter placed in parallel across the component, which can be analogue or digital.