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

$A$ 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:

The number of turns in the primary and secondary coils of a transformer are $50$ and $200$ respectively. If the current in the primary coil is $4 \,A$, then the current in the secondary coil is: (in $\,A$)

$A$ transformer may be used to provide maximum power transfer between two $AC$ circuits that have different impedances $Z_1$ and $Z_2$. The ratio of turns $N_1/N_2$ needed to meet this condition is given by :-

$A$ step-down transformer connected to an $AC$ mains supply of $220 \, V$ is made to operate a $11 \, V, 44 \, W$ lamp. Ignoring power losses in the transformer,what is the current in the primary circuit? (In $A$)

$A$ transformer is employed to