Question

A battery of emf $15\, V$ and internal resistance of $4\,\Omega$ is connected to a resistor. If the current in the circuit is $2 \,A$ and the circuit is closed. Resistance of the resistor and terminal voltage of the battery will be

• A. $2.5\,\Omega$, $6\,V$
• B. $3.5\,\Omega$, $6\,V$
• C. $2.5\,\Omega$, $7\,V$
• D. $3.5\,\Omega$, $7\,V$

Answer 1

Answer: (D)

$3.5\,\Omega$, $7\,V$

Answer 2

Given, $\varepsilon=15\,V$, $r=4\,\Omega$, $I=2\,A$ Now, for resistance of the resistors $\varepsilon-Ir=V=IR$; $15-2\times4=2\times R$; $15-8=2R$ $R=\frac{7}{2}=3.5\,\Omega$. Terminal voltage of battery, $V= IR = 2 \times 3.5 = 7 \,V$