Question

A certain household has consumed 250 units of energy during a month. How much energy is this in jouls.

Besides this question I have a doubt that 1 kWh = 3.6 × 10^6 J. How the value came, can you explain it please.

Answer 1

1 unit of energy = 1 kWh
250 units of energy = 250 kWh
Now, 1 kWh = 3.6 x 10^6 Joules (or Wsec)
Therefore, 250 kWh = 250 x 3.6 x 10^6 J
= 9 x 10^8 Joules.
b)1 Watt-sec (that’s a Ws) is a Joule… a watt expended for a second.
Because there’s 3600 seconds in an hour,
then 3600 Ws = 1 Wh = 3600 Joules = 3.6 kJ
so 1000 Wh = 1 kWh = 1000 x 3.6 kJ = 3.6 MJ=3.6×10^6joule