Year 9 Science · Unit 3 · Lesson 19
Apply Worksheet
Learning Goals
Order the steps
Number the steps from 1 to 6 to show the correct order for solving an Ohm's Law problem. Step 1 = what you do first.
| Order | Step |
|---|---|
| Check the unit of the answer (amps) and make sure it is reasonable | |
| Substitute the known values into the formula | |
| Identify the unknown quantity you need to find (V, I, or R) | |
| Compare the calculated current to the household circuit safety limit (10 A) | |
| Identify the two known values given in the problem | |
| Write the correct rearrangement of Ohm's Law (e.g. I = V ÷ R) |
Real-world context
An Australian household appliance, a bathroom towel rail, runs on the standard mains voltage of 240 V and has a resistance of 48 Ω. Australian domestic circuits are protected by circuit breakers rated at 10 A. If the current drawn by an appliance exceeds this limit, the circuit breaker will trip to prevent overheating and fire.
(a) Calculate the current drawn by the towel rail. Show all working, including the formula used and the correct unit in your answer.
Formula: I = V ÷ R Substitution: I = _____ ÷ _____ Answer: I = _____
(b) Does the towel rail exceed the 10 A household circuit safety limit? Explain what would happen if it did exceed the limit.
(c) What would happen to the current drawn if the resistance of the towel rail doubled to 96 Ω (while still connected to 240 V)? Calculate the new current and explain the result using Ohm's Law.
New current: I = _____ ÷ _____ = _____
Wrap Up
In one sentence, what was the main idea of this lesson?