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According ohm`s law v is directly proportional to current ..but according to I=p/v it is inversely proportional why?

According ohm`s law v is directly proportional to current ..but according to I=p/v it is inversely proportional why?

Grade:10

1 Answers

Eshan
askIITians Faculty 2095 Points
5 years ago
Dear student,

Let’s try to understand the concept of proportionality first.
IfA=kB, then we can say thatA\propto Bonly if k is a constant(or has been kept as a constant while making physical measurements of A and B).
Hence when we keep the resistance of a material fixed, that is, we do not change the shape or size of the material, and if then we increase voltage, we observe increase in current. Hence they are directly proportional.

However it is not the case when we talk about power. When we say thatP=VI, we are only changing the values of V and I and then ‘calculating’ the value of P. It is NOT that we give a voltage, ‘keep the power constant’, and then we try to measure current flowing. Hence when we writeI=\dfrac{P}{V}, we do not intend to keep P as a constant and hence we cannot say that V and I are inversely porportional.

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