Question

What is the potential drop between points A and C in the following circuit ? Resistances $1 \, \Omega$ and $2 \, \Omega$ represent the internal resistances of the respective cells.

• A. $1.75\,V$
• B. $2.25\,V$
• C. $\frac{5}{4}{V}$
• D. $\frac{4}{5} V$

Answer 1

Answer: (B)

$2.25\,V$

Answer 2

Emf's $E_{1}$ and $E_{2}$ are opposing each other.
Since, $E_{2}>E_{1}$ current will move from right to left.

Current in circuit
$i=\frac{E_{2}-E_{1}}{R+r_{1}+r_{2}}$
$=\frac{4-2}{5+1+2}=\frac{2}{8}=0.25 A$
The potential drop between points $A$ and $C$ is
$V_{A}-V_{C} =E_{1}+i r_{1}$
$=2+(0.25 \times 1)$
$=2.25 \,V$