Ohm's Law

Topic: Ohm’s Law (V = IR)

Aim: Recall and use Ohm’s law to predict the current in a simple circuit.

Quantities

Units

Open Ended

What do you think the picture shows us about circuits?

Vocabulary

Voltage - a measure of how much
energy the charges have. (measured in volts e.g. 1.5 V)

Current - flow of charges OR flow of
electricity (measured in amps e.g. 1 A)

Resistance - how much an object will
resist the flow of electric current (measured in ohms e.g. 100 Ω)

Match

Match the following quantities with their units.

• Current, I

• Voltage, V

• Resistance, R

• Energy, E

Amps, A

Volts, V

Ohms, Ω

Joules, J

• Amps, A

• Volts, V

• Ohms, Ω

• Joules, J

Open Ended

Type out and answer these sentences.

An iPhone charger's OUTPUT voltage is ___ . This means that each unit of charge delivers ___ joules of energy.

Open Ended

Type out and answer these sentences.

An iPhone charger's OUTPUT current is ___ . This means that ___ units of charge flows through the phone in one second.

Example

What is the current produced by a 9-V battery flowing through a resistance of 200 Ω?

Multiple Choice

What is the voltage if a resistance of 25 Ω has a current of 250 amperes?

Show your work.

• 6250 V

• 10 V

• 0.1 V

Multiple Choice

What is the current produced by a voltage of 240 V through a resistance of 0.2 Ω? Show your work.

• 1200 A

• 120 A

• 48 A

• 0.00083 A

A device that measures the current in a circuit. The ammeter also has two connections (black and red)

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​Ammeter

Ask for the materials: 2 batteries, 1 lightbulb, 1 ammeter, 3 wires.

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​Make this circuit.

Open Ended

Use the voltage of the battery and the current reading on the ammeter to estimate the resistance of the light bulb. (Show your work)

Open Ended

What happens to current when you connect two lightbulbs? Why do you think this happens?

(Key Words: current, voltage, resistance

Open Ended

Extension: What happens to current if you connect them like this? Why do you think this is?

(Key Words: current voltage resistance)