Question

Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:

1. the total current taken from the supply
2. the resistance of each heater and
3. the energy supplied in kWh to the three heaters in 5 hours.

Answer 1

Given,

Power, p = 250 w
Voltage, v = 100 v

1. Current through each heater, I = ?
   As p = VI
   I = `"P"/"V"`
   = `250/100`
   = 2.5 A
   ∴ Current taken for the three heaters = 3 × 2.5
   = 7.5 A
2. resistance for each heater, R = `"V"/"I"`
   = `100/2.5`
   = 40 Ω
3. Time for which energy is supplied, t = 5h
   As, Energy, E = p × t
   For each heater E = 250 × 5
   = 1250 wh or E = 1.25 kwh
   Energy for three heaters = 3 × 1.25
   = 3.75 kwh