An $80 \text{ W}$ lamp is connected to the secondary of a step-down transformer, where the primary is connected to an $AC$ mains of $220 \text{ V}$. Assuming the transformer to be ideal, the current in the primary winding is nearly: (in $\text{ A}$)

The transformation ratio in a step-up transformer is

$A$ small town with a demand of $900 \text{ kW}$ of electric power at $220 \text{ V}$ is situated $20 \text{ km}$ away from an electric power generating station. The two-wire line has a resistance per unit length of $5 \times 10^{-4} \text{ } \Omega \text{ m}^{-1}$. The town gets power from the line through a $45000 \text{ V}$ to $220 \text{ V}$ step-down transformer at a substation in the town. The line power loss in the form of heat is: (in $text{ kW}$)

$A$ 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 :-

$A$ transformer has a turn ratio of $100/1$. If the secondary coil has a $4 \, A$ current,then the current in the primary coil is......$A$

The efficiency of a transformer is very high because