How does frequency affect resistance?

Question

how does frequency affect resistance? please explain..

thank you!:D

Answer 1

Resistance is not affected by frequency.

In an A/C circuit the ratio of voltage to current is called

'Impedance' represented by 'Z' which is a complex quantity.

(V/I) = Z = R + jX.

'R' is the resistance and 'X' is the reactance. jX implies that V &   I are at quadrature. X is the sum of 'Inductive' (L) and 'Capacitive' (C) reactances. If 'f' is the frequency

X = 2pi f L - [1/2pi f C] .

As you can see X is a function of frequency (and not R that is unaffected by f) whose main effect is to introduce a phase difference between V & I.

Answer 2

Normally resistance is constant, over a small range, but the capacitance of the resistor comes into play at very high frequencies.  But you have to be dealing in very short microwaves for this to be much of a factor.  The capacitance of a resistor is very small, under a picofarad, probably, in thru-hole resistors.

Interesting question, as we don't usually take into effect resistance on frequency as other factors dominate.

Answer 3

resistance remains fairly constant, but if reactance(resistance of inductor/capacitor) will be affected.

for an inductor, reactance(X-L) is directly proportional to inductance(L).

    X-L = 2*pi*f*L

for an capacitor, reactance(X-C) is inversely proportional to capacitance(C).

   X-C = 1/ ( 2*pi*f*C)

Answer 4

If you are thinking about real ohmic resistance, it is no affected by the frequency. But if you are thinking about the no-ohmic resistance (impedance), then you must see the influence of the frequency through this:

Z = 1(w(L.C)^0,5) w = 2.pi.f, L is the inductance and C is the capacitance.

Bye