Practical electrical and electronic circuits

Series circuits

This is a series circuit.

Circuit with a cell, switch, and two lamps in series.

In a series circuit there is only one path for the current and the current is the same at all points.

Current in series circuits

We measure current using an ammeter.

An ammeter must be connected in series with other components in a circuit. This means we need to break into the circuit when we add an ammeter.

Simple circuit with a cell, switch, lamp and ammeter connected in series

The current in a series circuit is the same at all places in the circuit.

Circuit with a cell, closed switch and two lamps connected in series. An ammeter between the cell and switch is labelled 'Is = 3 A'; an ammeter after the first lamp is labelled 'I1 = 3 A'; and an ammeter after the second lamp is labelled 'I2 = 3 A'. Circuit with a cell, closed switch and two lamps connected in a series

We can write this current relationship as:

{I_s} = {I_1} = {I_2} = {I_3} =  ...

Question

Look at the series circuit below - what is the reading at?

Position one: more than 0.1A, 0.1A or less than 0.1A

Position two: more than 0.1A, 0.1A or less than 0.1A

Position three: more than 0.1A, 0.1A or less than 0.1A

Circuit with a cell, switch, ammeter and two lamps in series. Point 1 is between the switch and first lamp, point 2 is between the two lamps and point 3 is between the second lamp and the cell. The ammeter reads 0.1 A when the switch is closed.

Position 1 = 0.1A

Position 2 = 0.1A

Position 3 = 0.1A

Remember that the charge moves all the way around the circuit.