$A$ transformer with efficiency $80\%$ works at $4\, kW$ and $100\, V$. If the secondary voltage is $200\, V$, then the primary and secondary currents are respectively:

$A$ generator produces a current of $100 \, A$ at $4000 \, V$. The voltage is stepped up to $2 \times 10^5 \, V$ by a transformer before being sent on a high voltage transmission line of resistance $50 \, \Omega$. The percentage of power loss in the transmission line is (in $\%$)

$A$ step-down transformer is used to reduce the main supply from $V_1$ volt to $V_2$ volt. The primary coil draws a current $I_1$ $A$ and the secondary coil draws $I_2$ $A$. $(I_1 < I_2)$. The ratio of input power to output power is

$A$ step-up transformer operates on a $230\, V$ line and supplies a load of $2\, A$. The ratio of the primary and secondary windings is $1 : 25$. The current in the primary is.... (in $, A$)

The coils of a step-down transformer have $500$ and $5000$ turns. In the primary coil, an $AC$ current of $4 \,A$ at $2200 \,V$ is sent. The value of the current and potential difference in the secondary coil is:

$A$ transformer is used to light a $140\, W$, $24\, V$ lamp from a $240\, V$ $AC$ mains. The current in the main cable is $0.7\, A$. The efficiency of the transformer is......$\%$