Question

An electric heater operates at 200v and has a power of 1.5kw what current passes through the heater being used in and how to use many units of electricity are used when the heater is used for 2.30hrs

Answer 1

The current is

$$I=\frac PV=7.5\text{ A}$$

The energy within 2 hours 30 minutes is

$$E=Pt=1500·(2·3600+30·60)=13.5·10^6\text{ J}.$$

Or simply (but we need to use 2.5 hours)

$$E=Pt=1.5·2.5=3.75\text{ kW}·\text{h}.$$