1. 19/08/2015 Current, Charge & Power Objectives To apply equations of power, electrical energy and potential difference to different situations. HSW: AF2 – Understanding the applications and implications of science Used before in: lesson 3 – fuses and circuit breakers Will use again in: radioactivity PLTS: Team workers – Work collaboratively with others. Used before in: lesson 3 – fuses and circuit breakers Will use again in: radioactivity http://www.youtube.com /watch?v=b0JLnF9A9P0 &noredirect=1

2. 19/08/2015Outcomes All students should be able to apply the equation of power to different situations and understand that heat is given off by light bulbs and that different lights have different efficiencies. Most students should be able to recall the equation for power and apply the equations of charge and voltage to different situations. Some students may be able to derive the equation for electrical power and apply it.

3. 19/08/2015Power Power is “the rate of doing work”. The amount of power being used in is given by: E tP Power = Energy used ÷ time in W in J in sec How do light-bulbs make light? http://www.youtube.com/watch?v=YnMP1Uj2nz0 http://www.youtube.com/watch?v=YnMP1Uj2nz0 How do energy efficient light bulbs make light? http://www.youtube.com/watch?v=JpkIvyAUHVc http://www.youtube.com/watch?v=JpkIvyAUHVc Now read p248: Can you describe 3 reasons to choose CFLs over normal bulbs? (what does CFL stand for?)

4. 19/08/2015 Electrical Power Power is “the rate of doing work”. The amount of electrical power being used in is given by: P VI Power = Current x P.D in W in J in V

5. Power Questions 19/08/2015 1. Calculate the power of a television that uses 1200 J of energy in 4 seconds. 2. Calculate the power of a fire that uses 20 000 J of energy in 8 seconds. 3. Calculate the power of a drill that uses 36 000 J of energy in 1 minute. 4. Calculate the power of a radio that uses 144 000 J of energy in 2 hours. 5. Calculate the power of a kettle that uses 7.2 M J of energy in 120 minutes. 6.How much energy does a light bulb of power 60 W give off in 12 seconds? 7.How much energy does an electric fire of power 3000 W give off in 1 minute? 8.How much energy does a shower of power 7 kW give off in 300 seconds? 9.How much energy does a light bulb of power 40 W give off in 6 hours? 10.How much energy does a kettle of power 1.5 kW give off in 3 minutes? 11. Calculate the time taken for a television of power 200W to use 1000 J of energy. 12. Calculate the time taken for a fire of power 3000W to use 60 000 J of energy. 13. Calculate the time taken for a drill of power 150W to use 25 J of energy. 14. Calculate the time taken for a radio of power 2W to use 4 kJ of energy. 15. Calculate the time taken for a kettle of power 2kW to use 1 MJ of energy. 16. Calculate the power of a television that requires a current of 2A for a voltage of 230V. 17. Calculate the power of an electric fire that requires a current of 13A for a voltage of 230V. 18. Calculate the power of a light bulb that requires a current of 0.5A for a voltage of 230V. 19. Calculate the power of a charger that requires a current of 15mA for a voltage of 230V. 20. Calculate the power of a torch bulb that requires a current of 200mA for a voltage of 6V.

6. 19/08/2015 Charge (Q) As we said, electricity is when electrons move around a circuit and carry energy with them. Each electron has a negative CHARGE. Charge is measured in Coulombs (C). We can work out how much charge flows in a circuit using the equation: Q TI Charge = current x time (in C) (in A) (in s)

7. 19/08/2015 Example questions Charge (C)Current (A)Time (s) 52 0.41 200.5 50250 360 1)A circuit is switched on for 30s with a current of 3A. How much charge flowed? 2)During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for? 3)A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed?

8. Voltage 19/08/2015

9. Proving E=VxQ 19/08/2015 Charge = current x time (in C) (in A) (in s) Power = Current x P.D in W in J in V Power = Energy used ÷ time in W in J in sec

10. Quiz 19/08/2015 1What happens when electric current flows through a wire? 2How does a filament lightbulb work? 3How does an energy efficient lightbulb work? 4What is voltage? 5What is electric current? 6What is power? 7What is electrical power?