Question

A battery of e.m.f. $20\text{V}$ and internal resistance $6\Omega$ is connected to a resistor as shown in figure. If the current in the circuit is $1\text{amp}$, the resistance of the resistor will be:

• A. $14\Omega$
• B. $16\Omega$
• C. $28\Omega$
• D. $7\Omega$

Answer 1

Answer: (A)

$14\Omega$

The current running through a resistor when a battery with internal resistance is connected is given as:

$I=\frac{E}{R+r}$

here, $E=20V$, $r=6\Omega$

So, substitue the values:

$\frac{20}{R+6}=1$

$\Rightarrow 20=R+6$

$\Rightarrow R=14\Omega$