T=RC

T=Time Constant

R=Resistance in ohms

C= Capacitance in Farads

Time constant in an RC filter is resistance times capacitance. With ideal components, if the resistance is zero, then the time constant is zero, not mattter what the capacitance is. In a practical circuit, there is always some resistance in the conductors and in the capacitor so, if the resistance is (close to) zero, the time constant will be (close to) zero.

The time-constant is the resistance times the capacitance, so that's 47 x 47 and because the capacitance is in microfarads, the answer is in microseconds.

resistance (R)

inductance(L)

capacitance(C)

shunt conductance(G)

The product of resistance and capacitance is referred to as the time constant. It determines rate of charging and discharging of a capacitor.