Question

In post office box experiment, if Q/P=1/(10). In (R ) if 142 Omega is used then we get deflection towards right and if R =143 Omega , then deflection is towards left. What is the range of unknown resistance?

Answer 1

Given:

If $R = 142 \Omega$ , then deflection is towards right.

If $R = 143 \Omega$ then deflection is towards left.

    $\frac{Q}{P} = \frac{1}{10}$

To find:  The range of unknown resistance.

Solution:

We know that in a post office box

                 $\frac{P}{Q} = \frac{R}{X}$

                $X= \frac{Q}{P} \times R$

Putting value of      $\frac{Q}{P}$        

             $X = \frac{1}{10} \times R$

When            $R = 142 \Omega$  

                     $X = 14.2 \Omega$

and when        $R = 143 \Omega$

                       $X = 14.3 \Omega$

Thus, the unknown resistance $X$ lies between $14.2\Omega$ and  $14.3 \Omega$