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During a Thunderstorm the 'Live' Wire of the Transmission Line Fell Down on the Ground from the Poles in the Street. - CBSE (Science) Class 12 - Physics

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Question

During a thunderstorm the 'live' wire of the transmission line fell down on the ground from the poles in the street. A group of boys, who passed through, noticed it and some of them wanted to place the wire by the side. As they were approaching the wire and trying to lift the cable, Anuj noticed it and immediately pushed them away, thus preventing them from touching the live wire. During pushing some of them got hurt. Anuj took them to a doctor to get them medical aid.

Based on the above paragraph, answer the following questions :
(a) Write the two values which Anuj displayed during the incident.
(b) Why is it that a bird can sit on a suspended 'live' wire without any harm whereas touching it on the ground can give a fatal shock ?
(c) The electric power from a power plant is set up to a very high voltage before transmitting it to distant consumers. Explain, why.

Solution

a)  During this incident, Anuj reflected the following values:
(i) He was concerned about the lives of the individuals.
(ii) He was well aware about what would be the after effect of touching a live wire with naked hands and he immediately acted upon this situation and saved lives of the boys.

b)  When the bird perches on a live wire, its body becomes charged for the moment and has same voltage as the live wire; however, no current flows into its body. Body is a poor conductor of electricity as compared to the copper wire, so there is no reason for electrons to take a detour through the bird's body. Therefore, no current flows from the body of the bird.
On the other hand, if the bird touches the ground while being in contact with the high voltage live wire, then the electric circuit gets complete and high current flows through the body of the bird, giving it a fatal shock

c)The electric power from a power plant is set up at a very high voltage before transmitting it to distant consumers to reduce the loss of power during transmission.

The power loss during the transmission is equal to the I2R. So the power loss can be minimised by reducing the value of the current. Thus, to reduce the value of current, value of the voltage of the electric power should be kept high before transmitting.

Power = Voltage×Current

From the above equation, we can see that the current can be reduced by increasing the voltage of the electric power.

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Solution During a Thunderstorm the 'Live' Wire of the Transmission Line Fell Down on the Ground from the Poles in the Street. Concept: Electric Current.
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