Question

Why is the use of a.c voltage preferred over d.c voltage? Give two reasons.

Answer 1

Hint: A.C stands for alternating current. The AC source can be used in a transformer and can be stepped-up or stepped-down as per the requirement. Because AC voltage fluctuates from maximum value to minimum value which in turn induces the current in the secondary coil of the transformer. But as the DC contains only a certain value so it cannot be stepped up or stepped down.

Complete answer:
AC voltage is preferred over DC voltage because
(i) AC voltage can be transmitted to large distances with much less energy losses as compared to dc. Because the Heat produced in the wire is
$H={{i}^{2}}Rt$
In both AC and DC the resistance is high but the heat produced during the transmission can be reduced by decreasing current and increasing the potential difference. So that the amount of energy transmitted is not affected.
(ii) AC voltage can be adjusted i.e. can be stepped-up or can be stepped down as per the requirement. But DC voltage cannot be stepped up or stepped down. A transformer converts low voltage and high current electric energy at generating station into a low current and high voltage current. This high voltage electricity can be transmitted to large distant consuming stations. At the consuming station this voltage is stepped down in three stages by the use of step down transformers.

Note:
AC may have advantages but also have a major disadvantage. The main disadvantage is its effect on human life. AC can be very dangerous because its value increases and decreases and has more peak value than DC. So if we caught a live dc wire it will just throw us away but if we caught an ac live wire we will be act as a conductor and current will flow through our body so the signals from the brain will incapable of reaching different body parts and the person cannot break the contact with the live wire.