Question

A step down transformer reduces $220V$ to $110V$. The primary and secondary current are 5 and 9 amperes respectively. The efficiency of transformer is

• A. $20$%
• B. $4$%
• C. $90$%
• D. $100$%

Answer 1

Answer: (C)

$90$%

$\eta =\frac{E_s{I}_s}{E_p{I}_p}$

$\eta =\frac{110\times 9}{220\times 5}=0.9\times 100$% $=90$%