An electric motor, under load, has an effective resistance of 30 $\Omega$ and an inductive reactance of 40 $\Omega$.When powered by a source with a maximum voltage of 420 V, the maximum current is:
A)6.0 A
B)8.4 A
C)10.5 A
D)12 A
E)14 A

Question

Quizplus · Accepted Answer

We can use the maximum voltage and the total effective impedance (resistance + reactance) to calculate the maximum current according to Ohm's Law:

I(max) = V(max) / Z(total)

Z(total) = √(R^2 + X^2)      (where R is resistance and X is reactance)

I(max) = 420 V / √(30 Ω^2 + 40 Ω^2) = 420 V / 50 Ω = 8.4 A

Therefore, the answer is B)8.4 A as it is the closest option to the calculated value.

An Electric Motor, Under Load, Has an Effective Resistance of 30