A step-down transformer is used on a 1000V line to deliver 20A at 120V at the secondary coil. If the efficiency of the transformer is 80 % , the current drawn from the line is

Question

A step-down transformer is used on a 1000V line to deliver 20A at 120V at the secondary coil. If the efficiency of the transformer is 80 % , the current drawn from the line is (A) 3 A (B) 30 A (C) 0.3 A (D) 2.4 A

Tardigrade Admin · Accepted Answer

η %=(80/100)=(Vs Is/Vp Ip)=(120 × 20/1000 × Ip) Ip=(120 × 20/1000 × 0.8)=3 A

Q. A step-down transformer is used on a $1000 V$ line to deliver $20 A$ at $120 V$ at the secondary coil. If the efficiency of the transformer is $80%$ , the current drawn from the line is

$3 A$

$30 A$

$0.3 A$

$2.4 A$

$η % = \frac{80}{100} = \frac{V _{s} I _{s}}{V _{p} I _{p}} = \frac{120 \times 20}{1000 \times I _{p}}$
$I_{p} = \frac{120 \times 20}{1000 \times 0.8} = 3 A$

Q. A step-down transformer is used on a 1000V line to deliver 20A at 120V at the secondary coil. If the efficiency of the transformer is 80% , the current drawn from the line is

3A

30A

0.3A

2.4A