The discharge curve for a capacitor connected in series with a resistor is shown

Question

The discharge curve for a capacitor connected in series with a resistor is shown on the right. (a) is the maximum current in the resistor at the beginning or at the end of the discharge? Explain your answer. (b) If the capacitance of the capacitor is 0.05F, what is the resistance of the resistor? (c) After the capacitor is fully discharged, it is again charged. How much time after charging begins is the required for the potential difference across the capacitor to reach 10.0 volts. t is in seconds and VC is in volts.

Phn V. sted in series with Ronan current in of the discharge? of the capacitor is ser (c) After the aged OW much for the potential 100 volts. t is in 30.0 So .. .. ...................... . 20.0 Her a of a deal to start to are the o in e e - so I EU role set in an as we see on a peace treat 10 0 Enter Dir a SO r, as is. . . . . Second - - - - - - - 00 OGSD 100 1SD 20.0 25.0 30.0

Explanation / Answer

a) the maximum current is in the beginning, this is because , as the capacitor starts charging it gains potential itll it is equal to that of battery and hence short circuiting it. till it charges the current will drop across the resistor

b) given C = 0.05 F

R =?

now, lets see from the graph, at time t= 5 secs,

Vc= 10 V

Vmax = 30 V ( this is the potential of battery )

now, use the equation ,

t =-RC ln ( Vc/Vmax )

=> 10 = -R* 0.05 ln ( 10/30 )

=> R = 91.02 ohms

c) t = -RCln ( 10/30 )

so , we will get t= 5 secs

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