Question

A potentiometer wire has a length of 1.5 m and resistance of 10 ohm. It is connected in a series with the cell of emf 4 volt and the internal resistance 5 ohm. Calculate the potential drop per centimeter of the wire.

Answer 1

Given that,

Length = 1.5 m

Resistance = 10 ohm

Cell of emf = 4 volt

Internal resistance = 5 ohm

We need to calculate the current

Using formula of current

$I=\dfrac{E}{R+r}$

Where, I = current

E = emf

R = resistance

r = internal resistance

Put the value in to the formula

$I=\dfrac{4}{10+5}$

$I=\dfrac{4}{15}$

$I=0.26\ A$

We need to calculate the potential

Using ohm's law

$V=IR$

Put the value into the formula

$V=0.26\times10$

$V=2.6\ V$

We need to calculate the potential drop per centimeter of the wire

Using formula of potential drop per centimeter

$potential\ drop\ per\ centimeter=\dfrac{V}{l}$

Put the value into the formula

$potential\ drop\ per\ centimeter=\dfrac{2.6}{1.5\times100}$

$potential\ drop\ per\ centimeter=0.0173 V/cm$

Hence, The potential drop per centimeter of the wire is 0.0173 V/cm.