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Question
Sushil is in the habit of charging his mobile and then leaving the charger connected through the mains with the switch on. When his sister Asha pointed it out to him, he replied there was no harm as the mobile had been disconnected. Asha then explained to him and convinced him, how the energy was still being wasted as the charger was continuously consuming energy.
Answer the following questions :
(a) What values did Asha display in convincing her brother?
(b) What measures, in your view, should be adopted to minimise the wastage of electric energy in your households?
(c) Imagine an electric appliance of 2 W, left connected to the mains for 20 hours. Estimate the amount of electrical energy wasted.
Solution
(a) Asha displays the values of awareness towards energy saving and her concern towards wastage of energy.
(b) Following measures should be adopted to minimise the wastage of electric energy in our households:
(i) We should switch off the electrical appliances, which are not in use.
(ii) The old electrical appliances should be repaired time to time, as they often consume more electricity.
(iii) Condensers of electrical appliances should be replaced time to time.
(iv) New electrical and electronic appliances must be purchased in accordance with their efficiency to consume less energy.
(v) Use of solar devices like solar heater and cookers must be encouraged rather than the use of conventional electrical appliances.
(c) Electrical energy dissipated by an appliance is given by
\[E = P \times t\]
\[, \text { where P is the power and t is the time } . \]
\[P = 2 W\]
\[t = 20 h = 20 \times 60 \times 60 s\]
\[ \Rightarrow E = 2 \times 20 \times 60 \times 60\]
\[ \Rightarrow E = 1 . 44 \times {10}^5 J\]
