A refrigerator of 450 W works on a 230 V supply. Which fuse suits it: 3 A, 13 A or 30 A? Explain.

Step 1. Normal current. $I = \dfrac{450\ \text{W}}{230\ \text{V}} = 1.96\ \text{A}$.

Step 2. The choice. $3\ \text{A}$ is just above this. $13\ \text{A}$ or $30\ \text{A}$ would let a dangerous fault current flow before melting.