Circuit Devices and Types of Circuit

Pages 45-50

Explain how the resistance of an LDR varies with light intensity

In darkness, the resistance is the highest

What happens to the resistance of a thermistor as it gets colder

In cool conditions, the resistance goes up

True or false? Potential difference is shared between components in a series circuit

True

True or false? The current is constant in a series circuit

True - the current is the same everywhere

True or false? The potential difference across each component in parallel is different

False - the potential difference is the same across all components

Explain why adding resistors in parallel decreases the total resistance of a circuit, but adding them in a series increases the total resistance

• Both resistors have the same potential difference

• The pushing force is the same as the source potential difference for each resistor added

• By adding another loop, the current has more than one direction to go in

• This increases the total current that can flow around the circuit

• An increase in current means a decrease in total resistance

Describe an experiment that could be carried out to investigate how adding resistors in series and parallel affects the total resistance of a circuit

Series:

1. You need 4 identical resistors

2. Build the simple circuit shown and make a note of the potential difference of the battery

3. Measure the current through the circuit

4. Use this to calculate the resistance (R=V/I)

5. Add another resistor in series with the first

6. Measure the current again

7. Repeat steps 4 and 5 until you run out of resistors

8. Plot a graph

Parallel

1. Build the same circuit with the same equipment

2. Measure the current and calculate the resistance

3. Add another resistor in parallel with the first

4. Measure total current and calculate the resistance again

5. Repeat steps 3 and 4 until you run out of resistors

6. Plot a graph