Question

1. Following graph was plotted between V and I values:
What would be the values of V A ratios when the potential difference is 2 V.3 V and 5 V
respectively? What conclusion do you draw from these values?
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Answer 1

$\Large\underbrace{\underline{\sf{Understanding\: the\: Question}}}$

Here in this question, the main concept of verification of ohm's law is used. We are given a V-I graph and we are asked to find the ratio of V with respect to A. We know that ratio of V and I is resistance so, in simple words we are asked to find value of resistance with particular values of V and I. So firstly we will find the value of I from the graph when the value of V are 2V, 3V and 5V respectively. Then we will find the values of ratio of V and I.

So let's do it!

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From graph we obtained:

• When V is 2v then I is 0.2A

• When V is 3v then I is 0.3A

• When V is 5v then I is 0.5A

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~Now let's find ratio of V-I for first case (2v,0.2A)

${\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{V}{I}}$

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{2v}{0.2A}$

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{10v}{A}$

V/A is equal to R(resistance) so,

$\pmb{\mapsto\sf Ratio\:of\:V\!\!-\!I=10R}$

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~Now let's find ratio of V-I for second case (3v,0.3A)

${\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{V}{I}}$

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{3v}{0.3A}$

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{10v}{A}$

V/A is equal to R(resistance) so,

$\pmb{\mapsto\sf Ratio\:of\:V\!\!-\!I=10R}$

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~Now let's find ratio of V-I for third case (5v,0.5A)

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{V}{I}$

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{5v}{0.5A}$

$\mapsto\sf Ratio\:of\:V\!\!-\!I=\dfrac{10v}{A}$

v/A is equal to R(resistance) so,

$\pmb{\mapsto\sf Ratio\:of\:V\!\!-\!I=10R}$

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We obtained that ratio of V-I is constant for given values of V and I. Graph of V-I is a straight line. So the observation for the given graph is that resistance remains constant for a particular material.

According to ohm's law which is V=IR here R is said to be a constant value which is Verified from our above results. Values of R are coming out to be same. Hence this result verifies ohm's Law.

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★ More to know :-

• Ampere is represented by A

• Voltage is represented by V

• Resistance is represented by R

• Current is represented by I

• Current is measured by ammeter

• Voltage is measured by voltmeter

• S.I. unit of current is ampere

• S.I. unit of potential difference is voltage

• Resistance is ratio of voltage and ampere

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