Chapter: 12th Physics : Electromagnetic Induction and Alternating Current
Conservation of energy in LC oscillations
Conservation of energy in LC oscillations
During LC
oscillations in LC circuits, the energy of the system oscillates between
the electric field of the capacitor and the magnetic field of the inductor.
Although, these two forms of energy vary with time, the total energy remains
constant. It means that LC oscillations take place in accordance with
the law of conservation of energy.
Let us consider 3
different stages of LC oscillations and calculate the total energy of
the system.
Case (i) When the charge in the
capacitor, q = Qm and the current through the inductor, i
= 0, the total energy is
given by
The total energy is
wholly electrical.
Case (ii) When charge = 0 ;
current = Im , the total energy is
The total energy is wholly
magnetic.
Case (iii) When charge = q;
current = i, the total energy is
Since q = Qm
cos ωt, i = −dq/dt = Qmω sin ωt. The negative sign in
current indicates that the charge in the capacitor decreases with time.
From above three cases,
it is clear that the total energy of the system remains constant.
Related Topics