4.2.2 What is an RC Circuit?
Recall that the capacitance is defined as the proportionalityconstant between the total charge accumulated by a capacitor andthe voltage difference across the circuit
Q = Câ–³V (4.2)
In this equation, the charge Q is expressed in Coulomb (C), thevoltage â–³V, in volts (V) and the capacitance C in farads (F).
In this lab you will study both the charging and dischargingprocess of an RC circuit. During the charging process, anelectrical EMF source accumulates charges on each side of theparallel plate capacitor. During the discharging process, thecapacitor releases all its charges into the circuit (which now doesnot contain the battery). Capacitors charge and dischargeexponentially in time. During the discharge of a capacitor, theinstantaneous voltage â–³Vc between the ends of the capacitor alsodrops and is given by â–³VÑ = â–³Vmax*e^(-t/Ï„) (4.3) where â–³Vmax is themaximum voltage across the capacitor, i.e. the voltage to whichthecapacitor was initially charged, t is the time and Ï„ is the timeconstant given by Ï„= Req*Ceq (4.4) where Req and Ceq are,respectively, the equivalent resistance and capacitance to which wecan reduce the circuit. Although the theoretical discharge time isin nite, in practice we consider that the discharge is over whenthe voltage at the bounds of the capacitor is at 1% of its maximalvalue.
Answer the following questions in the Results section: Assumingthe voltage, when completely charged, is set to Vâ‚€ = 1 and byconsidering the variables Ï„ for time constant and t for time, whatare the equations for of charging and discharging? Support youranswer by physical arguments
