$A$ 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 $\%$)

Write two types of transformer.

How does a transformer affect the voltage and current?

$A$ transformer has $100$ turns in the primary coil and carries $8 A$ current. If the input power is $1 \text{ kW}$,the number of turns in the secondary coil,to have $500 \text{ V}$ output,will be $:-$

$A$ 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:

$A$ power transmission line feeds input power at $2.3 \text{ kV}$ to a step-down transformer with its primary winding having $3000$ turns. The output power is delivered at $230 \text{ V}$ by the transformer. The current in the primary of the transformer is $5 \text{ A}$ and its efficiency is $90 \%$. The winding of the transformer is made of copper. The output current of the transformer is . . . . . . $A$.