Which of the following is correct for a real transformer?

$A$ transformer has an efficiency of $80 \%$ and works at $10 \ V$ and $4 \ kW$. If the secondary voltage is $240 \ V$, then the current in the secondary coil is: (in $A$)

Which of the following statements is correct regarding a step-down transformer?

The instrument which works on the principle of mutual inductance is

$A$ distribution transformer with an efficiency of $90 \%$ supplies power to a colony of $10$ homes. All the $10$ homes have an electrical oven running at the same time,each drawing $20 \ A$ current from $220 \ V$ lines. The power dissipated as heat in the transformer is: (in $kW$)

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