Chapter 22, Problem 91A

To determine

To check : Whether the given device obey Ohm’s Law or not.

Answer to Problem 91A

The given device doesnot obey Ohm’s Law.

Explanation of Solution

Given:

A device similar to resistor is connected initially across 1.5-V battery and it measures a current of $45\times {10}^{-6}\text{ A}$ and then measures a current of $25\times {10}^{-3}\text{ A}$ when connected to a battery of 3.0-V

Formula used:

According to Ohm’s law, the voltage in a device is directly proportional to the current flowing through it and the proportionality constant is a characteristic of the device which is called resistance. So any device which follows this relationship obeys Ohm’s law. It can be expressed as,

  $V=IR$ …… (1)

Calculation:

In the first case, the ratio of voltage to the current which is the resistance is given by,

  $\begin{array}{c}{R}_1=\frac{V_1}{I_1}\\ =\frac{1.5}{45\times {10}^{-6}}\\ =33.33\text{k}\Omega \end{array}$

Now, considering the second case,

  $\begin{array}{c}{R}_2=\frac{V_2}{I_2}\\ =\frac{3}{25\times {10}^{-3}}\\ =120\Omega \end{array}$

It can be seen that, the voltage and current does not follow a linear relationship and the ratio is different in both cases. Hence, the given device does not obey Ohm’s Law

Conclusion:

The given device does not obey Ohm’s Law.