The primary winding of a transformer has $100$ turns and its secondary winding has $200$ turns. The primary is connected to an ac supply of $120 \,V$ and the current flowing in it is $10 \,A$. The voltage and the current in the secondary are

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

How much current is drawn by the primary coil of a transformer,which steps down $220 V$ to $55 V$ to operate a device with an impedance of $275 \Omega$ (in $A$)?

The output voltage of an ideal transformer,connected to a $240 \, V$ $a.c.$ mains,is $24 \, V$. When this transformer is used to light a bulb with rating $(24 \, V, 24 \, W)$,calculate the current in the primary coil of the circuit.

$A$ 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 $text{ kW}$)

$A$ step-up transformer has a turns ratio of $10:1$. $A$ cell of $e.m.f. = 5 \, V$ is connected to the primary coil. What is the secondary voltage developed?