Question

Three heaters each rated ${}^{\prime }250W,100V^{\prime }$ are connected in parallel to a $100V$ supply, calculate :
(i) the total current taken from the supply,
(ii) the resistance of each heater , and
(iii) the energy supplied in kWh to the three heaters in $5$ hours.

Answer 1

Given,
Power,$p=250w$
Voltage,$v=100v$
i) current through each heater,I=?
As$p=VI$
$\Rightarrow I=\frac{P}{V}$
$=\frac{250}{100}=2.5A$
$\therefore$ Current taken for the three heaters $=3\times 2.5=7.5A$
ii) resistance for each three heaters=$R=\frac{V}{I}$
$=\frac{100}{2.5}=40\Omega$
iii)Time for which energy is supplied, t=5h
As, $Energy,E=p\times t$
$=E=250\times 5=1250wh$
or$E=1.25kwh$
Energy for three heaters =3 x 1.25=3.75 kwh