heckpoint
Calculate the cost of leaving a laptop computer and a broadband modem on standby
for one week. The cost of one unit is 15p per kWh.
Electrical work done (kWh) = power (kW) X
A laptop computer transfers energy at a rate of
standby.
A broadband modem transfers energy at a rate of
standby.
= 168
Number of hours in one week = 24 x 7 =
Electrical work done by laptop in one week =
Electrical work done by modem in one week =
-
(h)
W =
W =104
kW x
kW x
Total work done =
+
= 2.688 kWh
2.688 kWh x 15p/kWh = p (to two significant figures)
kW when left on
kW when left on
h =
h =
kWh
kWh