Ohm's Law

Ohm's Law

Middle School

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Learning Objectives

Key Vocabulary

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Voltage (V)

The difference in electric potential between two points, which causes electrons to flow.

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Current (I)

The rate of flow of electric charge or electrons through a conductor material.

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Resistance (R)

The opposition to the flow of electric current, converting electrical energy into heat.

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Ohm's Law

A law stating that current is directly proportional to voltage and inversely proportional to resistance.

Measurements in Electricity

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Voltage (V)

• ​It is the difference in electric potential energy per unit charge between two points in a circuit.

• ​​This force causes electrons to flow from high to low voltage.

• ​The unit of measurement for voltage is the Volt (V).

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Current (I)

• ​Current is the rate of flow of electrons through a material.

• ​​It measures how fast or how much electricity is actually flowing.

• ​The unit for measuring the current is the Ampere (A).

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Resistance (R)

• ​Resistance opposes the flow of electrons through a given material.

• ​​It acts like friction and converts electrical energy into heat.

• ​Resistance is measured in a special unit called Ohms (Ω).

Multiple Choice

Which of the following is the measure of a material's opposition to the flow of electrons?

• Voltage (V)

• Current (I)

• Resistance (R)

• Potential Difference

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Ohm's Law

Multiple Choice

According to Ohm's Law, if the resistance in a circuit increases and the voltage remains the same, what happens to the current?

• It increases.

• It decreases.

• It stays the same.

• It becomes zero.

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Calculating with Ohm's Law

Multiple Choice

Using the formula $$$$ , what is the current in a circuit with a 24-volt battery and 6 ohms of resistance?

• 4 A

• 144 A

• 0.25 A

• 18 A

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Common Misconceptions

Misconception	Correction
Voltage and current are the same thing.	Voltage is the push on electrons; current is the flow of electrons.
Resistance is always bad.	Resistance is essential to control current and is used in many appliances.
Any amount of voltage is dangerous.	The danger of electric shock depends on the current, not only the voltage.

Multiple Choice

In a simple circuit, if you keep the voltage the same but use a wire with higher resistance, what will be the effect on the current?

• The current will increase because it has to work harder.

• The current will decrease because the flow of electrons is opposed more strongly.

• The current will stay the same because the voltage has not changed.

• The current will alternate directions.

Multiple Choice

Why is a material like copper, which is a good conductor, described as having low resistance?

• Because it has a high potential difference.

• Because it does not allow electrons to flow easily.

• Because it presents very little opposition to the flow of electrons.

• Because it converts a lot of electrical energy into heat.

Multiple Choice

A student wants to power a small motor that requires a current of 2 A to operate correctly. If the motor has a resistance of 6 Ω, what voltage battery should the student use?

• 3 V

• 8 V

• 12 V

• 0.33 V

Multiple Choice

A circuit contains a 20 V battery and a 10 Ω resistor. If you replace the 10 Ω resistor with a 5 Ω resistor, what will happen to the current?

• The current will be cut in half because the resistance is lower.

• The current will double because the resistance is lower.

• The current will stay the same because the battery voltage is constant.

• The current will increase to 25 A.

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Summary

Poll

On a scale of 1-4, how confident are you with applying Ohm's Law to solve problems?

• 1

• 2

• 3

• 4