Question

An electrical power line, having a total resistance of $2\Omega,$ delivers $1\, kW$ at $220\, V$. The efficiency of the transmission line is approximately:

• A. $72 \%$
• B. $96 \%$
• C. $91 \%$
• D. $85 \%$

Answer 1

Answer: (B)

$vi =10^{3}$
$i =\frac{1000}{220}$
loss $= i ^{2} R =\left(\frac{50}{11}\right)^{2} \times 2$
efficiency $=\frac{1000}{1000+ i ^{2} R } \times 100=96 \%$