NEET-XII-Physics
08: Electromagnetic Waves
- #2A parallel plate capacitor (Fig. 8.7) made of circular plates each of radius R = 6.0 cm has a capacitance C = 100 pF. The capacitor is connected to a 230 V ac supply with a (angular) frequency of 300 rad s-1.
(a) What is the rms value of the conduction current?
(b) Is the conduction current equal to the displacement current?
(c) Determine the amplitude of B at a point 3.0 cm from the axis between the plates.
Ans : Radius of each circular plate, R = 6.0 cm = 0.06 m
Capacitance of a parallel plate capacitor, C = 100 pF = 100 × 10-12 F
Supply voltage, V = 230 V
Angular frequency, ω = 300 rad s-1
(a) Rms value of conduction current, I
Where,
XC = Capacitive reactance
∴ I = V × ωC
= 230 × 300 × 100 × 10-12
= 6.9 × 10-6 A
= 6.9 μA
Hence, the rms value of conduction current is 6.9 μA.
(b) Yes, conduction current is equal to displacement current.
(c) Magnetic field is given as:
B
Where,
μ0 = Free space permeability
I0 = Maximum value of current =
r = Distance between the plates from the axis = 3.0 cm = 0.03 m
∴B
= 1.63 × 10-11 T
Hence, the magnetic field at that point is 1.63 × 10-11 T.
- #2-aWhat is the rms value of the conduction current?Ans : Rms value of conduction current, I
Where,
XC = Capacitive reactance
∴ I = V × ωC
= 230 × 300 × 100 × 10-12
= 6.9 × 10-6 A
= 6.9 μA
Hence, the rms value of conduction current is 6.9 μA.
- #2-bIs the conduction current equal to the displacement current?Ans : Yes, conduction current is equal to displacement current.
- #2-cDetermine the amplitude of B at a point 3.0 cm from the axis between the plates.
Ans : Magnetic field is given as:
B
Where,
μ0 = Free space permeability
I0 = Maximum value of current =
r = Distance between the plates from the axis = 3.0 cm = 0.03 m
∴B
= 1.63 × 10-11 T
Hence, the magnetic field at that point is 1.63 × 10-11 T.