$A$ transformer is used to light a $140\, W$, $24\, V$ lamp from a $240\, V$ $AC$ mains. The current in the main cable is $0.7\, A$. The efficiency of the transformer is......$\%$

$A$ 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 :-

Which of the following is correct for a real transformer?

$A$ step-up transformer operates on a $230 \ V$ line and a load current of $2 \ A$. The ratio of primary and secondary windings is $1:25$. Then the current in the primary is (in $A$)

An ideal transformer converts $220 \ V$ $AC$ to $3.3 \ kV$ $AC$ to transmit a power of $4.4 \ kW$. If the primary coil has $600$ turns,then the alternating current in the secondary coil is:

$A$ transformer works on