Question

A primary cell has an e.m.f of 1.5 volt. When short-circuited it gives a current of 3 ampere. The internal resistance of the cell is
A) 4.5 ohm
B) 2 ohm
C) 0.5 ohm
D) (1/4.5) ohm

Answer 1

Hint:This is a direct problem from the current electricity part of physics. We can directly substitute the values in the resistance formula and find its value.


Formula Used:
$r = \dfrac{E}{I}$
Where r = internal resistance, E = e.m.f of the cell and I current.


Complete answer:
The e.m.f and current of the cell is given. Substitute the values in the resistance formula.
$r = \dfrac{E}{I} = \dfrac{{1.5}}{3} = 0.5\Omega $

Hence, the correct option is Option (C).

Additional Information:
The electric potential created by an electrochemical cell or by modifying the magnetic field is referred to as electromotive force. The abbreviation for electromotive force is EMF. The Electromotive Force Formula is given below.
$\varepsilon = V + Ir$
Where $r$= internal resistance of the cell, $I$= current across the circuit, $V$= voltage of the cell and $\varepsilon $ = electromotive force (EMF)




Note: Volt is used to measure electromotive force. In other words, the work performed on a unit charge is referred to as EMF. The electromotive force (EMF) is independent of circuit resistance.