$A$ step-down transformer converts transmission line voltage from $11000 \, V$ to $220 \, V$. The primary of the transformer has $6000 \, \text{turns}$ and the efficiency of the transformer is $60 \%$. If the output power is $9 \, kW$, then the input power will be ........ $kW$.

$A$ common transistor radio set requires $12\,V$ $(D.C.)$ for its operation. The $D.C.$ source is constructed by using a transformer and a rectifier circuit,which are operated at $220\,V$ $(A.C.)$ on standard domestic $A.C.$ supply. If the number of turns in the secondary coil is $24$,then the number of turns in the primary coil is:

$A$ transformer is used to light a $100 \,W$ and $110 \,V$ lamp from a $220 \,V$ mains. If the main current is $0.5 \,A$, the efficiency of the transformer is approximately (in $\%$)

In a primary coil,a $5\,A$ current is flowing at $220\,V$. In the secondary coil,a voltage of $2200\,V$ is produced. The ratio of the number of turns in the secondary coil to the primary coil is:

Write the principle of a transformer.

In a step-up transformer,the voltage in the primary is $220\,V$ and the current is $5\,A$. The secondary voltage is found to be $22000\,V$. The current in the secondary (neglect losses) is......$A$.