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• November 16, 2022

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• PHY102 Physics II © Dr.Cem Özdoğan

• 27-9 RC Circuits, Discharging a Capacitor

• Discharging a Capacitor:

• Assume that the capacitor of the figure is fully charged (switch closed for a long time) to a potential V0 equal to the emf of the battery ξ.
• At a new time t =0, switch S is thrown from a to b so that the capacitor can discharge through resistance R.

• Fig. 27-16 (b) This shows the decline of the charging current in the circuit. The curves are plotted for R =2000 , C =1 F, and E =10 V; the small triangles represent successive intervals of one time constant .

• Time constant: τ= RC
• Time i drops to 1/e.

• i(t)=dq/dt=(ξ/R)e-t/RC

• q(t)/C=ξ=VC

• i(t)

• VR(t)+VC(t)=0

• exponential discharging

• C

• +

• 

• Stored charges find
• their way across the
• circuit, as establishing
• a current