Question

Just as a 100 Ω resistor always has the same resistance no matter what circuit it is in, likewise a 50 μF capacitor always has the same reactance no matter what circuit it is in. Answer: FALSE why?

Answer 1

The resistance of the resistor does not depend upon the frequency. So, both in AC and DC circuits the resistance remains the same.

The reactance of a capacitor depends upon the frequency of the AC source. If the capacitance of the capacitor is C and the frequency of the AC source is , then the reactance of the capacitor is given by
   
And so, as the frequency changes, the reactance changes. For very high frequency , the reactance decreases, and for the low frequency , the reactance increases. And for DC circuit, = 0. And so, in this case the reactance is infinity.
This implies that the reactance of the capacitor is not a constant and it changes depending upon the values of the frequency of the source.