Calculate the operating current (I) of the electric heater using the formula P = VI, where P is power and V is voltage.

$$I = \frac{P}{V}$$ $$I = \frac{2000 \text{ W}}{240 \text{ V}}$$ $$I = \frac{200}{24} \text{ A}$$ $$I = \frac{25}{3} \text{ A}$$ $$I \approx 8.33 \text{ A}$$

Comparing $8.33 \text{ A}$ with the given options:
A: 3 A (too low)
B: 5 A (too low)
C: 10 A (suitable, as it's the next standard rating above 8.33 A)
D: 13 A (also above, but 10 A provides closer protection)

The most suitable fuse is 10 A.

The correct option is C.

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A17 What is the operating resistance of an electric lamp rated 60W, 240V?

$P = \frac{V^2}{R}$.
Rearrange the formula to solve for resistance:

$$R = \frac{V^2}{P}$$

$$R = \frac{(240 \text{ V})^2}{60 \text{ W}}$$ $$R = \frac{240 \times 240}{60} \Omega$$ $$R = \frac{57600}{60} \Omega$$ $$R = 960 \Omega$$

A: 4 $\Omega$
B: 300 $\Omega$
C: 960 $\Omega$
D: 14 400 $\Omega$

The calculated resistance is $960 \Omega$.

The correct option is C.