$A$ power transmission line feeds input power at $2300\; V$ to a step-down transformer with its primary windings having $4000$ turns. What should be the number of turns in the secondary in order to get output power at $230\; V$?

$1\, MW$ power is to be delivered from a power station to a town $10\, km$ away. One uses a pair of $Cu$ wires of radius $0.5\, cm$ for this purpose. Calculate the fraction of ohmic losses to power transmitted if
$(a)$ power is transmitted at $220\, V$. Comment on the feasibility of doing this.
$(b)$ a step-up transformer is used to boost the voltage to $11000\, V$,power is transmitted,then a step-down transformer is used to bring voltage to $220\, V$.
Given: $\rho_{Cu} = 1.7 \times 10^{-8}\, \Omega \cdot m$.

In an ideal step-down transformer, out of the following quantities, which quantity increases in the secondary coil?

$A$ power transformer is used to step up an alternating $e.m.f.$ of $220\,V$ to $11\,kV$ to transmit $4.4\,kW$ of power. If the primary coil has $1000$ turns,what is the current rating of the secondary (in $,A$)? Assume $100\%$ efficiency for the transformer.

$A$ transformer having efficiency $90 \%$ is working on $200 \ V$ 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 are respectively:

The quantity that remains unchanged in a transformer is: