Question

Five resistors are connected in circuit as shown with a 3 V battery. Find the ammeter reading.

• A. 1 A
• B. 2 A
• C. 3 A
• D. 4 A

Answer 1

The correct option is A 1 A

Given,
Resistance values,
$R1=R2=R3=3\Omega$
$R4=R5=0.5\Omega$

Here the resistances $R1$ and $R2$ are in series. Let the equivalent resistance of this combination be $R_{12}$.
$R_{12}=R1+R2$
$R_{12}=3+3=6\Omega$

Now $R_{12}$ and $R3$ are in parallel.
Let the equivalent resistance of this combination be $R_{123}$.

$⟹\frac{1}{R_{123}}=\frac{1}{R_{12}}+\frac{1}{R3}$
$\frac{1}{R_{123}}=\frac{1}{6}+\frac{1}{3}$
$R_{123}=2\Omega$

Now, $R4,R_{123}$ and $R5$ are in series.
Let the equivalent resistance of this combination be R.

$⟹R=R4+R_{123}+R5$
$R=0.5+2+0.5\Omega$
$R=3\Omega$

Using Ohms law,
$I=\frac{V}{R}$
$I=\frac{3V}{3\Omega }=1A$