1. Resistance
WALT: Describe the relationship between resistance and current and explain how different components can change resistance Starter: Draw the symbol of a variable resistor and explain one use it has

2. LDR (Light Dependent Resistor)
Has low resistance in bright light
and high resistance in low light
Used in security alarm
Draw a sketch of a graph to show the relationship between resistance and light intensity with an LDR

3. Thermistors
Thermistors detect temperature and are designed to decrease the resistance in a circuit as temperature increases
They are used in fire alarms
Draw a sketch of a graph to show the relationship between temperature and resistance with a thermistor

4. You have 2 minutes to quickly set up a circuit using a variable resistor, a bulb and an ammeter
Adjust the variable resistor and observe the changes in the bulb and ammeter, then sit down

5. Design an experiment to test the resistance of different lengths of wire
Now (before you start), write down:
1. Equipment needed
2. The circuit diagram
3. Prediction
4. Method
5. Results table

6. When finished: Write a conclusion
Investigate an LDR– Set up a circuit to test your theory that LDRs have low resistance in bright light. Use a torch (or light bulbs) and an ammeter. Draw the circuit diagram and explain what you observed.
PREP: Draw a graph of your results for length of wire against current

7. Plenary – Discuss in pairs what you have found out this lesson
As resistance increases, current decreases
Resistance increases as:
Length of wire increases
Thickness of wire decreases
Different types of wire have different levels of resistance
An electric current flows when electrons move through a conductor, such as a metal wire. The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance.
The resistance of a long wire is greater than the resistance of a short wire because electrons collide with ions more often.
The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current.