Download KS4 Electricty - Resistance, Power and Energy

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Valve RF amplifier wikipedia , lookup

Operational amplifier wikipedia , lookup

Nanofluidic circuitry wikipedia , lookup

CMOS wikipedia , lookup

Power electronics wikipedia , lookup

Josephson voltage standard wikipedia , lookup

TRIAC wikipedia , lookup

Lumped element model wikipedia , lookup

Switched-mode power supply wikipedia , lookup

Wilson current mirror wikipedia , lookup

Surge protector wikipedia , lookup

Opto-isolator wikipedia , lookup

Negative resistance wikipedia , lookup

Two-port network wikipedia , lookup

Multimeter wikipedia , lookup

Power MOSFET wikipedia , lookup

Rectiverter wikipedia , lookup

Resistive opto-isolator wikipedia , lookup

Electrical ballast wikipedia , lookup

Current source wikipedia , lookup

Network analysis (electrical circuits) wikipedia , lookup

Current mirror wikipedia , lookup

Ohm's law wikipedia , lookup

Transcript
KS4 Electricity – Resistance
© Boardworks Ltd 2003
Teacher’s Notes
A slide contains teacher’s notes wherever this icon is
displayed -
To access these notes go to ‘Notes Page View’
(PowerPoint 97) or ‘Normal View’ (PowerPoint 2000).
Notes Page View
Normal View
Flash Files
A flash file has been embedded into the PowerPoint
slide wherever this icon is displayed –
These files are not editable.
© Boardworks Ltd 2003
Use a textbook or other resource to fill in the table below:
Component
Circuit symbol
Diode
Variable Resistor
Thermistor
Light Dependent
Resistor
© Boardworks Ltd 2003
How are current and voltage related for a
resistor?
Set up the circuit as shown below:
Slowly move the variable resistor and for
each setting record the current in amps
and the voltage in volts.
Plot a graph of your results.
A
V
P.D.
(V)
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
I
(A)
0
0.6
1.1
1.8
2.5
3.0
3.5
4.2
© Boardworks Ltd 2003
Current and voltage
x
x
x
x
x
x
x
x
Potential difference / V
Draw
adoes
line
of
best
fit
for
Plot
your
points
on
the
graph.
If you
get
a your
straight
line
it means
What
graph
look
like?
your
graph.
that the
two quantities current
and voltage are proportional.
What does proportional mean?
If you double the voltage
then the current doubles.
This fact was put into a law:
Ohm’s Law:
The current flowing through a wire is proportional to the
potential difference (voltage) across it provided the
temperature remains constant. Georg Ohm 1826
© Boardworks Ltd 2003
Electron flow and Resistance
Electricity in wires is a flow of electrons along the wire. As the electrons
move along the wire they collide with the metal atoms. These collision
make the atoms vibrate more…which makes the metal hotter.
Resistance is a measure of how much a material tries to stop
electricity passing through it.
© Boardworks Ltd 2003
V=IR
We can express Ohm’s Law mathematically using the equation:
Voltage = Current x Resistance
V=IR
Voltage measured in Volts (V)
Current measured in Amps (A)
Resistance measured in Ohms ()
© Boardworks Ltd 2003
Formula triangles
Formula triangles help you to rearrange formula, the
triangle for the Ohm’s Law is shown below:
Whatever quantity you are trying to find cover it up
and it will leave you with the calculation required.
So if you were
trying to find
current, I…..
…you would
cover I up…
…and you are left
with the sum…

V
I
R

I = V
R
x
© Boardworks Ltd 2003
Formula triangles
© Boardworks Ltd 2003
Resistance for a bulb
If you have a filament bulb and it has a current of
20A running through it, with a potential difference of
100V across it, what is the resistance of the bulb?
V = IR
R = V/I
R = 100V/20A
R =5
© Boardworks Ltd 2003
Current for a diode
A diode has a current of 5A running through it, and a
resistance of 5. What is the potential difference
across the diode?
V = IR
V = 5A x 5
V = 25V
© Boardworks Ltd 2003
Resistors in series
Total resistance = R1 + R2
4
2
What is the total resistance for the circuit shown?
Total resistance = R1 + R2
Total resistance = 4  + 2 
Total resistance = 6 
© Boardworks Ltd 2003
Resistors in series
What is the total resistance for the circuit shown?
6
34
Total resistance = R1 + R2
Total resistance = 6  + 34 
Total resistance = 40 
© Boardworks Ltd 2003
Resistors in parallel
Total resistance = R1xR2
R1+ R2
4
2
What is the total resistance for the circuit shown?
Total resistance = 4 x 2
4 + 2
= 1.33
© Boardworks Ltd 2003
Resistors in parallel
What is the total resistance for the circuit shown?
8
6
Total resistance = 8 x 6
8 + 6
= 3.4
© Boardworks Ltd 2003
Voltage/current graphs
I
1
I
2
V
I
3
V
V

4
V

1. A wire or resistor.
2. A filament lamp.
3. Wires of different materials.
4. A diode.
..partly
x
I

Which of the components obeys Ohms Law?
© Boardworks Ltd 2003
P=IV
We can express the relationship between current,
voltage and power mathematically using the equation:
Power = Current x Voltage
P=IV
Voltage measured in Volts (V)
Current measured in Amps (A)
Power measured in Watts (W)
© Boardworks Ltd 2003
Formula triangles
Formula triangles help you to rearrange formula, the
triangle for the Power Law is shown below:
Whatever quantity you are trying to find cover it up
and it will leave you with the calculation required.
So if you were
trying to find
current, I…..
…you would
cover I up…
…and you are left
with the sum…

P
I
V

I = P
V
x
© Boardworks Ltd 2003
Power calculations
If you have a filament bulb and it has a potential
difference of 200V across it and a current of 0.2A running
through it. At what power is the bulb operating at?
P = IV
P = 0.2A x 200V
P = 40W
© Boardworks Ltd 2003
Power calculations
If you have a filament bulb and it operates at a power of
60W and it has a potential difference of 240V across it,
what is the current running through the bulb?
P = IV
I
= P/V
I
= 60W / 240V
I
= 0.25A
© Boardworks Ltd 2003
kV, kJ, kW
1 kV = 1000 V
1 kJ = 1000 J
1 kW = 1000 W
How many Volts in 6kV?
6 000 V
_________
How many Joules in 12.3kJ?
12 300 J
_________
How many Watts in 0.6kW?
600
_________
W
© Boardworks Ltd 2003
kV, kJ, kW
1 kV = 1000 V
1 kJ = 1000 J
1 kW = 1000 W
How many kiloVolts in 9 000V?
9.0
_________
kV
23.5
How many kiloJoules in 23 500J? _________
kJ
How many kiloWatts in 325W?
0.325 kW
_________
© Boardworks Ltd 2003
What are the units of resistance?
A. Amps
B. Ohms

C. Volts
D. Watts
© Boardworks Ltd 2003
What does the circuit symbol shown represent?
A. Voltmeter
B. Variable resistor
C. Light dependent resistor
D. Thermistor

© Boardworks Ltd 2003
What causes resistance?
A. Inertia
B. Friction

C. Buoyancy
D. Viscosity
© Boardworks Ltd 2003
If two resistors of 6  and 4  are placed in
parallel, what is their total resistance in the
circuit?
A. 10 
B. 2 
C. 2.4 

D. 24 
© Boardworks Ltd 2003
If a resistor that obeys Ohm’s Law has a
potential difference of 10V across it and a
current of 5A running through it.
What is its resistance?
A. 50 
B. 2 

C. 0.5 
D. 15 
© Boardworks Ltd 2003