what does d.c. stand for? what does a.c. stand for? what do you currently know about the electricity...
TRANSCRIPT
• What does d.c. stand for?
• What does a.c. stand for?
• What do you currently know about the electricity you get from a household plug? Voltage, frequency etc….
Starter
• By the end of today:– You should know what is meant by
direct and alternating current.
– You should be able to recall the frequency of mains electricity.
– Most will be able to describe in detail how an oscilloscope can be used to measure the frequency.
5.1 Electric Circuits
• What is ac and dc?• http://www.bbc.co.uk/learningzone/clips/
direct-current-vs-alternating-current/4557.html
• Why is ac used?• http://www.bbc.co.uk/learningzone/clips/a-
short-history-of-direct-and-alternating-current/1870.html
Learning Tasks….1. Silently read pages 184-1852. Define, as fully as possible:
• Frequency• Live Wire• Neutral Wire• Oscilloscope• Y gain control• Time base control
3. What is the frequency and voltage of a mains circuit?
4. Summary questions 1 and 2 page 185
• By the end of today:– You will be able to name all the parts of
a plug and describe their function.
– You will be able to explain why they are made of certain materials.
– You will have had a go at wiring a plug
6.2 Cables and Plugs
6.2 Cables and Plugs
Blue wire NeutralBrown wire LiveGreen and Earthyellow stripes
Remember!
BLUE bottom Left
BROWN bottom Right
STRIPED goes Top
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page
Component Function Material Reason
Case
Pins
Fuse
Cable Grip
Outer Cable
Inner wire
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page 6.2 Cables and Plugs
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/mainselecact.shtml
By the end of this lesson (or finished for homework)
Produce a guide for the
incompetent on ‘how to
wire a plug’.
You choose how
to present your
work.
–Pages 188-189–What is a fuse used for? How does it work?
Draw a quick diagram with your explanation.
–What is a circuit breaker used for? How does this work?
–Why do we ‘earth’ large electrical devices?–SQ 1 and 2
Power Power (watts) = Energy Transformed (joules)
Time (seconds)
This means the more powerful something is, the more energy is transferred every second.
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Power Power (watts) = Energy Transformed (joules)
Time (seconds)
For example:
If a bulb transforms 300 J of electrical energy into light in 3 second, the power is:
P = Energy Transformed ÷TimeP = 300 (J) ÷ 3 (s)P = 100 W
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Power in a circuit Power = Current x Potential Difference
(watts, W) = (ampere, A) x (volts, V)
P = I x V
For example:
If a bulb has a p.d. across it of 3.0V, and a current flowing through it of 2.0A then the power is:
P = I x VP = 2.0 (A) x 3.0 (V)P = 6.0 W
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Charge in a circuit Charge = Current x Time
(coulomb, C) = (ampere, A) x (seconds, s)
For example:
How much charge flows if a current of 2.0 A flows for 60 seconds?
Charge = Current x TimeCharge = 2.0 (A) x 60 (s)Charge = 120 C
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