Question

A transformer connected to a 120V (rms) AC line is to supply 12 kV (rms) for a neon sign. To reduce shock hazard, a fuse is to be inserted in the primary circuit; the fuse is to blow when the rms current in the secondary circuit exceeds 2.0 mA. What is the current (rms) in the primary circuit when the fuse blows?

Answer 1

$V_{2} = 12 kV= 12\times 10^{3} V$

$I_{2} = 2.0 mA= 2.0\times 10^{-3} A$

11 12V2 Vi

$I_{1} =\frac{2.0\times 10^{-3}A\times 12\times 10^{3} V }{120 V}$

the current (rms) in the primary circuit is