Question

A transformer has $100$ turns in the primary coil and carries $8\text{A}$ current. If input power is $1\text{kW}$, then number of turns in the secondary coil to have $500\text{V}$ output will be

• A. $100$
• B. $200$
• C. $400$
• D. $300$

Answer 1

The correct option is C $400$

For ideal transformer

$P_{in}=P_{out}=1000\text{W}$

$P_{out}=V_S{I}_S$

Current in secondary circuit is
$I_S=\frac{P_{out}}{V_S}=\frac{1000}{500}=2\text{A}$

Turns ratio of transformer gives
$\frac{I_P}{I_S}=\frac{N_S}{N_P}$

$N_S=\left(\frac{I_P}{I_S}\right)N_P=\left(\frac{8}{2}\right)100=400$