Transcript Transmission of electricity 2

Transmission of Electricity
Learning Outcomes
• Explain in terms of energy efficiency and safety, why electricity
is transmitted at high voltages but used at low voltages.
• Investigate the operation of ‘step up’ and ‘step down’
transformers.
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• Select and use the equation Power = Voltage x Current (P=V x I)
Transmission of Electricity
Key Words:
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• Power: The rate of flow of energy
Transmission of Electricity
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What do you remember
from last lesson?
Transmission of Electricity
Power = Voltage x Current
When we send electricity through a step up transformer, it increases the
voltage and decreases the current
This means that the power
always stays the same
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We want to send electricity at as low a current as possible because this
means less energy will be lost in the power lines as heat.
Power (Watts)
Voltage (Volts)
Current (Amps)
6
6
1
6
3
2
6
2
3
6
1
6
6
0.5
12
Transmission of Electricity
Why do we need step down transformers?
Step down transformers lower the voltage and raise the current
(the power stays the same)
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We need to use low voltages for safety!
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Transmission of Electricity
Transmission of Electricity
Power = Voltage x Current
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P=VxI
P
=
V
x
I
V=P
I
I=P
V
Transmission of Electricity
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Example 1:
My laptop has a power rating of 76W, it uses 4A of current.
What Voltage does my laptop require?
Transmission of Electricity
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Example 2:
The average home uses around 1000W of electricity. Houses use
electricity at 240V. What is the current used by the house?
Transmission of Electricity
Today, you guys are going to be the teachers.
A select few of you will come to the front, sum up the lesson,
and then question the class!
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Who’s brave enough to take up the challenge?