To find reactance

Sounds like homework.... but interesting anyway!

for dc only the internal resistance will cause power consumption, so at 40 volts dc if the power consumed is 150 Watt the resistance is...

P = V²/R therefore R=V²/P = 10.667 Ω

Now the problem! what frequency is the ac signal??

John.

I'm with you John, to find "ac resistance" you need to work out the inductive reactants of the device then only can work out the wattage. Frequency is fundamental to the formulae.

As calculated in the previous post,

R = V^2/P = 40 * 40/150 = 10.667 Ohms

Now I don't think the OP has got the question quite right though, because this resistive component is the only part that will dissipate power, so if 1375W is consumed at 240V AC, the resistance would be R=240 * 240 / 1375 = 41.89 Ohms, which is at odds with the previous result.

Let's assume that the coil consumes 1375 VA at 240V AC. This then means that the total impedance of the coil is 41.89 Ohms.

Now, we can use the formula Z^2 = R^2 + X^2 where Z is total impedance, R is the resistance and X is the reactance.

Hence Reactance X = Sqrt(Z^2 - R^2) = sqrt((41.89 * 41.89) - (10.67 * 10.67)

so X = 40.5 Ohms.

Got the same numbers here too...

Bill

Absolutely on Dot.Now u need the frequency to calculate the Inductance L from X i e inductive reactance.But that is not asked.so OK

I am sure when your teacher gave you that assignment he did not intend for you to get a ready made answer here.

You should at least try it on your own, and post your answer here for review.

power/voltage is the current.then voltage/current is the impedance.if the power factor from the input power is known then the reactance canbe calculated