If a capacitor with capacitance C and charged with a charge Q_{0} is connected to a resistor of resistance R, it starts to discharge in a process that is described by the formula Q(t) = Q_{0}exp(t/τ) , where τ = RC is the time constant (or the relaxation time) of the R - C circuit. In a time t = τ, the charge of the capacitor will decrease by a factor of e = 2,7. In the process of discharge, the energy stored in the capacitor is released on the resistor as heat.