Question

If a 50 W lamp is lit for 2 hours, the amount of electrical energy converted into heat and light is
a) 3.6 x 10J
b) 3.6 x 10-5J
c) 3.6 x 104 J
d) 3.6 x 104 J

Answer 1

50×2×60×60=3.6×10^5 J

Answer 2

total electric energy in kWh =( 50/1000)× 2

= 1/10kWh = 0.1 kWh

we know that 1kwh = 3.6 × 10^6j

so 0.1 kWh = 3.6 × 10^6 × 0.1

= 3.6 × 10^5 j