1. Additional Physics – Forces L/O :- To be able to recognise potential difference – current graphs Potential difference – current graph Exam Date -

2. L/O :- To be able to recognise potential difference – current graphs Potential difference – current graph Answers in the back of your books 1.How can you work out resistance in a circuit? 2.What affects the resistance in a wire? 3.What is the equation for working out current? 4.Does current split down branches of a parallel circuit? 5.Does voltage split down branches of a parallel circuit?

3. L/O :- To be able to recognise potential difference – current graphs Potential difference – current graph True or false: 1.The shorter the wire the lower the resistance. 2.The thicker the wire the lower the resistance. 3.The material of the wire can affect the resistance in the wire. 4.The hotter the wire the higher the resistance. 5.The straighter the wire the lower the resistance.

4. Quick quiz 1.What 2 factors affects your momentum? 2.How can you work out resistance in a circuit? 3.What affects the resistance in a circuit? 4.What is acceleration measured in? 5.What is the equation for work done and what is it measured in? 6.What is the equation for working out current? 7.Name 3 things which can affect stopping distance Time limit 5 minutes

5. Graph paper Plot the results of your resistance experiment.

6. Resistance in different materials Vid clip

7. Ohm’s law Ohm’s Law The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor In other words; The current goes up at a constant rate with the voltage {only under same temperature}

8. Resistance and Ohms Law Video clip

9. Current (A)00.050.10.150.20.25 Potential Difference (V)00.511.522.5 Potential Difference (V) 0 0.5 1 1.5 2 2.5 Current (A) 0.25 0.2 0.15 0.05 What does this graph tell you about the relationship between potential difference and voltage in a resistor at a constant temperature? REMEMBER - Ohm’s Law The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor You will need to be able to recognise this graph! This resistor supports Ohm’s Law.

10. What do these graphs tell you about each component? Get in pairs and write down what you can tell from each graph? Filament BulbDiode

11. What do these graphs tell you about each component? REMEMBER – The flatter the graph the higher the resistance Filament BulbDiode

12. What do these graphs tell you about each component? REMEMBER – you must be able to recognise these graphs Filament BulbDiode The filament bulb follows ohms law at low temperatures. At higher currents the temperature increases, so it doesn’t follow Ohms law. The diode has a high resistance in one direction. So it resists the flow of electrons in that direction.

13. Diodes are electronic components that can be used to regulate the potential difference in circuits Light-emitting diodes (LEDs) give off light and are often used for indicator lights in electrical equipment The diode has a very high resistance in one direction – this means that current can only flow in one direction The filament lamp is a common type of light bulb (it contains a thin coil of wire called the filament) The filament heats up when an electric current passes through it, and produces light as a result The filament lamp does not follow Ohm’s Law – its resistance increases as the temperature of its filament increases. As voltage increases the bulb gets hotter, and its resistance increases

14. What have you learnt? What do these graphs represent?