Rahul after having lived in US for 12 years returned back to India. He had a discussion with his cousin Sumit on domestic power supply in US and in India.In US domestic power supply is at 110V, 50Hz, whereas in India it is 220V, 50Hz.. Rahul was stressing that US supply is better than Indian supply. Both went to Sumit's father an electrical Engineer and asked his opinion on the issue. He explained that both the supplies have advantages as well as disadvantages.
1. What values are used by Rahul and Summit?
2. Write one advantage and one disadvantage of 220V supply over 110V supply.

Mr.Ramesh a physics teacher, was doing an experiment in lab using dry cell battery. The dry cell was weak, giving less voltage, which was not sufficient to give proper reading. One of the students asked, "Sir, can't we step-up the voltage using a transformer?" Teacher replied, "No, we cannot step up DC voltage using step up transformer and explained the reason and working of a transformer". The student then constructed a transformer for his physics project and studied the factors responsible for losses in a transformer.
1. What values are displayed by the student?
2. Why can transformer not be used to step-up DC voltage?

Rita noticed that the transformer in her locality gets damaged quite often leading to long power cuts. She complained to the power distribution company with the help of her father and got the transformer replaced?
(i) What is the principle of a transformer?
(ii) Mention two losses which take place in a transformer.
(iii) Values exhibited by Rita in dealing with the above situation.