Question

Question 7.8: Suppose the initial charge on the capacitor in Exercise 7.7 is 6 mC. What is the total energy stored in the circuit initially? What is the total energy at later time?

Class 12 - Physics - Alternating Current Alternating Current Page-266

Answer 1

According to question 7.7,

Capacitance ( C ) = 30 цf

1 цf = 10⁻⁶ f

=> 30 цf = 30 * 10⁻⁶ f

Inductance ( L ) = 27 mH

1 mH = 10⁻³ H

=> 27 mH = 27 * 10⁻³ H

Charge of the conductor ( Q ) = 6 mC

1 mC = 10⁻³ C

=> 6 mC = 6 * 10⁻³ C

We know that,

Energy = Q² / 2C

=> Energy = ( 6 * 10⁻³ )² / 2 * 30 * 10⁻⁶

=> Energy = 36 * 10⁻⁶ C / 60 * 10⁻⁶ F

=> Energy = 36 / 60 = 6 / 1 0= 0.6 J

Hence energy stored is 0.6 J.

This energy will be same in later time also as it is shared between Inductor and capacitor.