Question

an electricbheater of power 3kw is used fo 10 h how much energy does it consume in joule

Answer 1

H = P × t
= 3 × 10
= 30 J

Answer 2

$1kj = 1000j \\ 1hr = 3600s \\ so \: 10hrs = 36000 \\ h = p.i \\ h = 1000 \times 36000 \\ h = 36000000j$