Biography, Science, Technology, Health, History Blogs

Example of electromagnetic waves Example 1 :   A parallel plate capacitor with plate area A and separation between the plates d is charged by a constant current I. consider a plane surface of area A/3 parallel to the plates and drawn symmetrically between the plates. Find the displacement current through this area. Solution :   Let Q be the charge on the capacitor at time t. The electric field intensity at a point in between the plates of the capacitor is: E = Q/ϵ 0 A The electric flux through the area considered is ɸ E =(Q/ϵ 0 A)A/3=Q/3 ϵ 0 The displacement current is I D= ϵ 0 ( dɸ E /dt) = ϵ 0 d/dt(Q/3 ϵ 0 ) = ϵ 0 × i/3 ϵ 0 ( dQ/dt)= i/3 Example 2 : find the energy stored in a 120 cm length of a laser beam operating at 6m W. Solution : time taken by laser beam to move through a distance 120 cm is T= 120/c=120/(3 × 10 10 ) = 4 × 10 -9 s The energy contained in the 60 cm length of laser beam is U = P × t=6 m W × (4 × 10 -9 s ) =( 6 × 10 -3   j/s) ...