A capacitor is charged to a potential of 12.0 Vand is then connected to a voltmeter having an internal resistance of 3.10 MΩ. After a time of 4.10 sthe voltmeter reads 3.2 V.
Part A: What is the capacitance of the circuit?
Part B: What is the time constant of the circuit?

Respuesta :

Answer:

(A). The capacitance of the circuit is [tex]2.31\times10^{-6}\ F[/tex].

(B). The time constant of the circuit is 7.16 sec.

Explanation:

Given that,

Potential = 12.0 V

Internal resistance = 3.10 MΩ

Time = 4.10 s

Voltage = 3.2 V

(A). We need to calculate the capacitance of the circuit

Using formula of capacitance

[tex]V_{C}=V_{0}(e^{\dfrac{-t}{RC}})[/tex]

Put the value into the formula

[tex]3.2=12.0e^{\dfrac{-4.10}{3.10\times10^{6}C}}[/tex]

[tex]e^{\dfrac{-4.10}{3.10\times10^{6}C}}=0.267[/tex]

[tex]\dfrac{-4.10}{3.10\times10^{6}C}=log 0.267[/tex]

[tex]C=\dfrac{-4.10}{3.10\times10^{6}\times log0.267}[/tex]

[tex]C=0.000002306\ F[/tex]

[tex]C=2.31\times10^{-6}\ F[/tex]

The capacitance of the circuit is [tex]2.31\times10^{-6}\ F[/tex]

(B). We need to calculate the time constant of the circuit

Using formula of time constant

[tex]\tau=R\times C[/tex]

Put the value into the formula

[tex]\tau=3.10\times10^{6}\times2.31\times10^{-6}[/tex]

[tex]\tau=7.16\ sec[/tex]

The time constant of the circuit is 7.16 sec.

Hence, (A). The capacitance of the circuit is [tex]2.31\times10^{-6}\ F[/tex].

(B). The time constant of the circuit is 7.16 sec.