19/04/23

Current, Charge & Current, Charge & PowerPower

ObjectivesTo 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

19/04/23

OutcomesOutcomes• 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.

19/04/23

PowerPower

Power is “the rate of doing work”. The amount of power being used in is given by: E

tPPower = Energy used ÷ time

in W in J in sec

How do light-bulbs make light?http://www.youtube.com/watch?v=YnMP1Uj2nz0

How do energy efficient light bulbs make light? http://www.youtube.com/watch?v=JpkIvyAUHVc

Now read p248: Can you describe 3reasons to choose CFLs over normalbulbs? (what does CFL stand for?)

19/04/23

Electrical PowerElectrical Power

Power is “the rate of doing work”. The amount of electrical power being used in is given by: P

VIPower = Current x P.D

in W in J in V

Power QuestionsPower Questions 19/04/23

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.

19/04/23

Charge (Q)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)

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Example questionsExample questions

Charge (C) Current (A) Time (s)

5 2

0.4 1

20 0.5

50 250

3 60

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?

VoltagVoltagee

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Proving E=VxQProving E=VxQ19/04/23

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

QuizQuiz19/04/23

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