Give scientific reasons:In practice the unit kWh is used for the measu

1.	Give scientific reasons:In practice the unit kWh is used for the measurement of electric energy, rather than the joule.
Answer» (1) If an electric device rated 230 V, 5 A is operated for one hour, electric energy used = VIt = 230 V × 5 A × 3600 s = 4140000 joules. (2) If this energy is expressed in kW.h, it will be \(\frac{4140000}{3.6\times10^6}\) kW·h = 1.15 kW·h (more convenient). 3.6 × 10⁶ Hence, in practice the unit kW·h is used for the measurement of electric energy, rather than the joule.

Give scientific reasons:In practice the unit kWh is used for the measurement of electric energy, rather than the joule.

Answer»

(1) If an electric device rated 230 V, 5 A is operated for one hour, electric energy used

= VIt = 230 V × 5 A × 3600 s = 4140000 joules.

(2) If this energy is expressed in kW.h, it will be \(\frac{4140000}{3.6\times10^6}\) kW·h = 1.15 kW·h (more convenient). 3.6 × 10⁶

Hence, in practice the unit kW·h is used for the measurement of electric energy, rather than the joule.