In a transformer,the number of turns in the primary coil is $140$ and that in the secondary coil is $280$. If the current in the primary coil is $4 \ A$,then the current in the secondary coil is (in $A$):

In a step-down transformer,the number of turns in:

The quantity that remains unchanged in a transformer is:

$A$ power transmission line feeds input power at $2300 \, V$ to a step-down transformer with its primary windings having $4000$ turns. The output power is delivered at $230 \, V$ by the transformer. If the current in the primary of the transformer is $5 \, A$ and its efficiency is $90 \%$,the output current would be......$A$.

$A$ transformer having an efficiency of $90 \%$ is working on a $200 \ V$ and $3 \ kW$ power supply. If the current in the secondary coil is $6 \ A$,the voltage across the secondary coil and the current in the primary coil respectively are:

$A$ step-down transformer is used on a $1000\,V$ line to deliver $20\,A$ at $120\,V$ at the secondary coil. If the efficiency of the transformer is $80\%$,the current drawn from the line is ......$A$.