Question

The boiler has a rated power of 3 kW and is connected to a cylinder with a total capacity of 200 L. Measuring with a flask it takes five seconds to fill up half a litre of water determine how long it will take to warm up the water to 50°C from cold (take cold as 10°)

Answer 1

200 L of water are 200 kg. The energy required to rise the temperature of 200 kg of water from 10 to 50° is

$$Q=cm\Delta t.$$

The time is

$$T=\frac{Q}{P}=\frac{cm\Delta t}{P}=\\\space\\=11200\text{ s, or 187 min, or 3 h 6 min}.$$