Question

which use more energy, a 250 watt Tv set in 1 hr or a 1200 watt toaster in 20 minutes?​

Answer 1

ANSWERS :-

(I) For Tv set :-

power, p = 250 W = 250/1000kW = 0.25kW

Time, t = 1hr

So,

Electric energy, E = p * t

(used by Tv set) E = 0.25 * 1kWh

uses E = 0.25kWh

(ii) For toaster :-

power, p = 1200 W = 1200/1000kW

= 1.2kW

Time, t = 20min =20/60h =0.333h

So,

Electric energy, E = p * t

(used by toaster) E = 1.2 * 0.333kWh

E = 0.40kWh

From the above calculations, it is clear that the toaster uses more energy (0.40kWh) whereas tv set uses less energy(0.25kWh).

Answer 2

Answer:

Explanation:

For T.V set

Power (P) = 250w, Time (t) = 1hr=60×60=3600s

For Toaster

Power (P) = 1200w, Time (t) = 10min=10×60=600s

We know that Energy (E) = P×t

∴ Energy consumed by a TV set = 250 × 3600 = 9 × 105J

∴ Energy consumed by a toaster = 1200 × 600 = 7.2× 105J

∴ the energy consumed by a 250 W TV set in 1 h is more than the energy

consumed by a toaster of power 1200 W in 10 minutes.