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