Question

The input and output voltages of a transformer are $220$ V and $44$ V respectively. Find the current in input circuit if the output current is $2$ A.

• A. $2$ A
• B. $0.2$ A
• C. $4$ A
• D. $0.4$ A

Answer 1

Answer: (D)

$0.4$ A

A voltage change from primary to secondary will mean a current change also. As the input and output power are same:
$P=V_1{I}_1=V_2{I}_2$
if the voltage is increased the current will be decreased and vice versa.
Hence, the turn rule is stated as $Vp\times Ip=Vs\times Is$.

That is, $\frac{Vs}{Vp}=\frac{Ip}{Is}$

Where,
$Is=$current in the secondary coil
$Ip=$ current in the primary coil
$Vs=$ voltage across the secondary coil
$Vp=$ voltage across the primary coil
According to the question given, the input and output voltages of a transformer are $220$ V and $44$ V respectively. Let $x$ be the input voltage and the output voltage is $2$ A.
Then,

$\frac{44}{220}=\frac{x}{2}$

So, $x=2\times \frac{44}{220}$ That is, $x=0.4$ A.

The input current in the transformer is $0.4$ A