Question

750 w electric heater plugged into 240 v power supply. A trolley passing caused insulation distort and reduced resistance between live and netral to 60 ohms.
1. what is the rate of heat production in watts
2. plug fitted carries 3 amps fuse is this correct for appliance
3. would correctly rated fuse blown as result of fault

Answer 1

Answer on Question #42956-Physics-Electric Circuits

750 w electric heater plugged into 240 v power supply. A trolley passing caused insulation distort and reduced resistance between live and neutral to 60 ohms.

1. what is the rate of heat production in watts

Solution

$$N = \frac {U ^ {2}}{R} = \frac {240 ^ {2}}{60} = 960 \ W.$$

2. plug fitted carries 3 amps fuse is this correct for appliance

Solution

This is incorrect:

$$I _ {\text {heater}} = \frac {750}{240} = 3.125 \text{A} > I _ {\text {fuse}} = 3 \text{A}.$$

That's why electric heater wouldn't work.

3. would correctly rated fuse blown as result of fault

Solution

Yes, correctly rated fuse would blow as result of fault because $I_{\text{fault}} = \frac{U}{R} = \frac{240}{60} = 4A$ is bigger than $I_{\text{fusecorrect}} = 3.125A$.

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