$A$ 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 $\%$)

The primary of a transformer has $100$ turns and operates at $100 \,V - 200 \,W$. The number of turns in the secondary,if the output voltage is $2000 \,V$,is:

$A$ transformer consists of $500$ turns in the primary coil and $10$ turns in the secondary coil with a load of $10\, \Omega$. Find the current in the primary coil when the voltage across the secondary coil is $50\, V$. (in $A$)

$A$ transformer is employed to reduce $220\, V$ to $11\, V$. The primary draws a current of $5\, A$ and the secondary $90\, A$. The efficiency of the transformer is......$\%$

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

$A$ current of $5 \,A$ is flowing at $220 \,V$ in the primary coil of a transformer. If the voltage produced in the secondary coil is $2200 \,V$ and $50 \%$ of power is lost, then the current in the secondary will be (in $A$)