AQA GCSE Resistors
A resistor is an electrical circuit component that can affect the size of the current in a circuit.
All components in a circuit have resistance, so any component could be a resistor.
Resistors are either ohmic resistors, so they follow Ohm’s law, or non ohmic resistors so they do not follow Ohm’s law.
Ohm’s Law
Ohm’s law state that the current which flows through a resistor (component) is directly proportional to the potential difference across the resistor, providing that the temperature is constant. As shown in the graph.
Testing resistors to find out if they are ohmic conductors.
This is a practical that can be used to find out if a conductor is an ohmic conductor. The component under test could be a wire, filament bulb, or diode.
1.Variable resistor is used to set a range of resistance values.
2. At each resistance value, the switch is closed to complete the circuit.
3. The current through the component and potential difference across the component are recorded
4. Once readings are recorded, switch is opened to prevent wire overheating
5. A current-potential difference graph is then drawn, if it shows a directly proportional relationship, as shown in the graph above, then the conductor is an ohmic conductor.
The graphs below show the results for a length of wire, bulb and diode
Practice Questions
1.State Ohm’s Law
2. Draw a data table to collect the data for the testing resistors experiment above
3. Describe and explain the current-potential difference graph for a length of wire
4.Describe and explain the current-potential difference graph for a bulb
5. Describe and explain the current-potential difference graph for a diode.