Current transfers energy around circuits. Circuit components have various properties that can be measured and then used to make circuits for control and also circuits for testing other components.

There are different ways to investigate resistor networks. In this required practical activity, it is important to:

- record potential difference and current accurately
- use appropriate apparatus and methods to measure potential difference and current to work out resistance

To compare the total resistance in series and parallel arrangements.

- Set up the circuit as shown in figure 1, turn the power supply on and close the switch.
- Record the voltmeter and ammeter readings and calculate the resistance of the resistor using R = V/I, where R is resistance, V is potential difference and I is current.
- Change the resistor and repeat step two to find the resistance of a second resistor.
- Arrange the two resistors in series as shown in figure 2 and close the switch.
- Record the voltmeter and ammeter readings once again and determine the total resistance of both resistors in series using R = V/I.
- Arrange the two resistors in parallel as shown in figure 3 and close the switch.
- Record the voltmeter and ammeter readings once again and calculate the total resistance of both resistors in parallel.

Here are what the results could look like:

Resistor | Potential difference / V | Current / A | Resitance / Ω |
---|---|---|---|

R_{1} | 4.00 | 0.40 | 10 |

R_{2} | 4.00 | 0.40 | 10 |

In series | 4.00 | 0.20 | 20 |

In parallel | 4.00 | 0.80 | 5 |

- in series, the resistance of the network is equal to the sum of the two individual resistances
- in parallel, the resistance of the network is less than either of the two individual resistances

Placing the resistors in series causes the resistance to be double that of a single resistor because there is only one path for the electrons to follow - the supply must drive current through one resistor and then the other.

Placing the resistors in parallel causes the resistance to be half that of a single resistor.

The outcomes of this experiment are the same using filament lamps, or combinations of resistors and lamps, as the lamps act as resistors.

Hazard | Consequence | Control measures |
---|---|---|

Heating of wires and resistors | Minor burns | Set up circuit before closing the switch |