Ohm's Law Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Ohm's Law.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

The relationship stating that voltage across a conductor equals the current through it multiplied by its resistance.

More push (voltage) means more flow (current). More resistance means less flow for the same push.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Voltage, current, and resistance are linked — knowing any two lets you calculate the third.

Common stuck point: Ohm's law applies to individual components, not always to the whole circuit at once.

Worked Examples

Example 1

easy
A 12 \text{ V} battery is connected to a 4 \text{ } \Omega resistor. What current flows?

Solution

  1. 1
    Apply Ohm's law: I = \frac{V}{R}.
  2. 2
    Substitute the values: I = \frac{12}{4}.
  3. 3
    I = 3 \text{ A}

Answer

I = 3 \text{ A}
Ohm's law (V = IR) is the fundamental relationship in circuit analysis. It connects voltage, current, and resistance in a simple linear relationship.

Example 2

medium
A heater draws 5 \text{ A} from a 240 \text{ V} supply. What is its resistance, and how much power does it consume?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
What voltage is needed to push 0.25 \text{ A} through a 100 \text{ } \Omega resistor?

Example 2

medium
A resistor in a circuit has a current of 0.5 \text{ A} flowing through it when connected to a 6 \text{ V} supply. (a) What is its resistance? (b) If the voltage is doubled to 12 \text{ V}, what is the new current (assuming constant resistance)?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

voltageresistanceelectric current