Figure shows an iron-cored transformer assumed to be 100% efficient. The ratio of the secondary turns to the primary turns is 1:20.

A 240 V ac supply is connected to the primary coil and a `6 Omega` resistor is connected to the secondary coil. What is the current in the primary coil?

Options

A. `0.10 A`
B. `0.14 A`
C. 2A
D. 40 A

Answer

A

Explanation

The equivalent primary load is
`R_(1) = ((N_(1))/(N_(2))^(2)) R_(2) = ((20)/(1))^(2) (6.0) = 2400 Omega`
Current in the primary coil
` = (240)/(R_(1)) = (240)/(2400) = 0.1 A`