5.5 ohms law
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5.5 Ohm’s LawApril 12, 2023
Number of 1.5 V cells
Battery voltage / V Current / mA
1
2
3
4
5
6
Copy down this table please
Learning objectives
• Investigate the relationship between V, I and R• Show that I = V/R and plot I against V• Practise using I = V/R
Number of 1.5 V cells
Battery voltage / V
Current / mA
1
2
3
4
5
6
Number of 1.5 V cells
Battery voltage / V
Current / mA
1 1.5 75
2 3.0 150
3 4.5 225
4 6.0 300
5 7.5 375
6 9.0 450
1 2 3 4 5 6 7 8 9 100
50
100
150
200
250
300
350
400
450
500
A graph to show I vs V
Voltage / V
Curr
ent /
mA
1 2 3 4 5 6 7 8 9 100
50
100
150
200
250
300
350
400
450
500
f(x) = 50 x
A graph to show I vs V
Voltage / V
Curr
ent /
mA
Ohm’s Law
I
VR
Resistance
Current
Voltage
V
I R
Worked example 1
• A circuit has a voltage of 12 V and a resistance of 100 Ω. What is the current going around the circuit?
Worked example 1
• A circuit has a voltage of 12 V and a resistance of 100 ohms. What is the current going around the circuit?
AI
V
R
VI
IRV
I
R
VV
10/1120
12
?
120
12
Question 1
• What is the current in the circuit?
200 Ω
6 V
Question 2
• What is the value of the resistor in this circuit?
150 mA
3 V
Question 3
• What is the electromotive force from the cell?
100 mA
500 Ω
Ohm’s law
• The current through a conductor is proportional to the voltage across it – provided the temperature remains constant
• An electric current causes heating which makes things complicated
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