Transcript PowerPoint

29/03/2016
http://www.youtube.com
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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 Will use again in: radioactivity
and circuit breakers
PLTS: Team workers – Work collaboratively with others.
Used before in: lesson 3 –
fuses and circuit breakers
Will use again in: radioactivity
Outcomes
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• 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.
Power
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Power is “the rate of doing work”.
The amount of power being used in
is given by:
Power = 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 3
reasons to choose CFLs over normal
bulbs? (what does CFL stand for?)
E
P
t
Electrical Power
Power is “the rate of doing work”.
The amount of electrical power
being used in is given by:
Power = Current x P.D
in W
in J
in V
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P
I
V
Power Questions
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1.
2.
3.
4.
5.
Calculate the power of
Calculate the power of
Calculate the power of
Calculate the power of
Calculate the power of
a television that uses 1200 J of energy in 4 seconds.
a fire that uses 20 000 J of energy in 8 seconds.
a drill that uses 36 000 J of energy in 1 minute.
a radio that uses 144 000 J of energy in 2 hours.
a kettle that uses 7.2 M J of energy in 120 minutes.
6.
7.
8.
9.
10.
How much energy does a light bulb of power 60 W give off in 12 seconds?
How much energy does an electric fire of power 3000 W give off in 1 minute?
How much energy does a shower of power 7 kW give off in 300 seconds?
How much energy does a light bulb of power 40 W give off in 6 hours?
How much energy does a kettle of power 1.5 kW give off in 3 minutes?
11.
energy.
12.
energy.
13.
14.
15.
Calculate the time taken for a television of power 200W to use 1000 J of
Calculate the time taken for a fire of power 3000W to use 60 000 J of
Calculate the time taken for a drill of power 150W to use 25 J of energy.
Calculate the time taken for a radio of power 2W to use 4 kJ of energy.
Calculate the time taken for a kettle of power 2kW to use 1 MJ of energy.
16.
Calculate the power
of 230V.
17.
Calculate the power
voltage of 230V.
18.
Calculate the power
voltage of 230V.
19.
Calculate the power
of 230V.
20.
Calculate the power
voltage of 6V.
of a television that requires a current of 2A for a voltage
of an electric fire that requires a current of 13A for a
of a light bulb that requires a current of 0.5A for a
of a charger that requires a current of 15mA for a voltage
of a torch bulb that requires a current of 200mA for a
Charge (Q)
29/03/2016
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:
Charge = current x time
(in C)
(in A)
Q
(in s)
I
T
Example questions
Charge (C)
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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?
Voltage
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Proving E=VxQ
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
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Quiz
1
2
3
4
5
6
7
29/03/2016
What happens when electric current flows through a wire?
How does a filament lightbulb work?
How does an energy efficient lightbulb work?
What is voltage?
What is electric current?
What is power?
What is electrical power?