Three identical cells each of e.m.f. 2 V and unknown internal resistance are connected in parallel. This combination is connected to a 5 ohm resistor. If the terminal voltage across the cells is 1.5 volt, what is the internal resistance of each cell?

Solution

Effective emf of three cells in parallel, ε = 2 V
Internal resistance, r=?
External resistance, R= 5 ohm
Terminal voltage across the cell, V= 1.5 V
Let, internal resistance of each cell be 'r' ohm.
Effective internal resistance of each three cells in parallel, r= r/3
Therefore,
Total resistance of circuit $= \frac{r}{3} + R .$
Now we have,
$V = \frac{εR}{r + R}$

Terminal voltage, $V = \frac{ε \times R}{(r / 3) + R}$
$\Rightarrow$ $1.5 = \frac{2 \times 5}{(r / 3) + 5}$
$\Rightarrow$ $r = 5 Ω$

For Daily Free Study Material Join wiredfaculty

Current Electricity

Three identical cells each of e.m.f. 2 V and unknown internal resistance are connected in parallel. This combination is connected to a 5 ohm resistor. If the terminal voltage across the cells is 1.5 volt, what is the internal resistance of each cell?

Some More Questions From Current Electricity Chapter

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Phone Number

Email Address

Location