Transcript Energy Transformed (joules)

Starter
• 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….
6.1 Alternating
Current
5.1 Electric Circuits
• 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.
• What is ac and dc?
• http://www.bbc.co.uk/learningzone/clips/dir
ect-current-vs-alternatingcurrent/4557.html
• Why is ac used?
• http://www.bbc.co.uk/learningzone/clips/ashort-history-of-direct-and-alternatingcurrent/1870.html
Copy
this
page
WhatDirect
about this?
Alternating
What is the peak-to-peak voltage?
How long (in seconds) is it for one complete wave?
Learning Tasks….
1. Silently read pages 184-185
2. 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
6.2 Cables
and Plugs
In pairs devise five questions that
could have the answer:
A 3 pin plug.
6.2 Cables and Plugs
• 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
Copy
this
page
6.2 Cables and Plugs
Blue wire
Brown wire
Green and
yellow stripes
Neutral
Live
Earth
Remember!
BLUE bottom Left
BROWN bottom Right
STRIPED goes Top
6.2 Cables and Plugs
Component Function
Case
Pins
Fuse
Cable Grip
Outer Cable
Inner wire
Material
Copy
this
page
Reason
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.
Why does a three pin plug
have three pins?
Why is one pin longer
than the others?
–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
6.4 Power and
Potential
Difference
Power
Copy
this
page
Power (watts) = Energy Transformed (joules)
Time (seconds)
This means the more powerful something is, the
more energy is transferred every second.
Power
Copy
this
page
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 ÷Time
P = 300 (J) ÷ 3 (s)
P = 100 W
Power in a circuit
Power = Current x Potential Difference
(watts, W) = (ampere, A) x (volts, V)
P=IxV
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=IxV
P = 2.0 (A) x 3.0 (V)
P = 6.0 W
Copy
this
page
6.5 Energy
and Charge
Charge in a circuit
Copy
this
page
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 Time
Charge = 2.0 (A) x 60 (s)
Charge = 120 C
Energy in a circuit
Copy
this
page
Energy Transformed = Potential Difference × Charge
(joules, J)
= (volts, V) x (coulomb, C)
For example:
How much energy is transformed when the p.d. is
30V and the charge is 2.0 C?
Energy = Potential Difference × Charge
Energy = 30 (V) x 2.0 (C)
Energy = 60 J