Question

A battery of emf $10V$ and internal resistance $3$ is connected to a resistor. The current in the circuit is $0.5A$. The terminal voltage of the battery when the circuit is closed is

• A. $10V$
  
• B. $0V$
  
• C. $8.5V$
  
• D. $1.5V$
  

Answer 1

Answer: (C)

$8.5V$

Emf of the battery $E=10$ volts

Internal resistance of the cell $r=3\Omega$

Current flowing through the circuit $I=0.5A$

Potential drop across internal resistance $V=Ir$

$\therefore$ $V=0.5\times 3=1.5$ volts

Thus terminal voltage of the battery $V_1=E-V$

$\therefore$ $V_1=10-1.5=8.5$ volts