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In free space, which of the following will be zero?
c) Conductivity Explanation: In free space, ε = ε0 and μ = μ0. The relative permittivity and permeability will be unity. Since the free space will contain no charges in it, the conductivity will be zero.
c) Conductivity
Explanation: In free space, ε = ε0 and μ = μ0. The relative permittivity and permeability will be unity. Since the free space will contain no charges in it, the conductivity will be zero.
See lessIn good conductors, the electric and magnetic fields will be
b) 45 out of phase Explanation: The electric and magnetic fields will be out of phase by 45 in good conductors. This is because their intrinsic impedance is given by η = √(ωμ/σ) X (1+j). In polar form we get 45 out of phase.
b) 45 out of phase
Explanation: The electric and magnetic fields will be out of phase by 45 in good
See lessconductors. This is because their intrinsic impedance is given by η = √(ωμ/σ) X (1+j). In polar form we get 45 out of phase.
If the loss tangent is very less, then the material will be a
b) Lossless dielectric Explanation: If loss tangent is less, then σ /ε ω <<1. This implies the conductivity is very poor and the material should be a dielectric. Since it is specifically mentioned very less, assuming the conductivity to be zero, the dielectric will be lossless (ideal).
b) Lossless dielectric
Explanation: If loss tangent is less, then σ /ε ω <<1. This implies the conductivity is very poor and the material should be a dielectric. Since it is specifically mentioned very less, assuming the conductivity to be zero, the dielectric will be lossless (ideal).
See lessThe ratio of conduction to displacement current density is referred to as
c) Loss tangent Explanation: Jc /Jd is a standard ratio, which is referred to as loss tangent given by σ /ε ω. The loss tangent is used to determine if the material is a conductor or dielectric.
c) Loss tangent
Explanation: Jc /Jd is a standard ratio, which is referred to as loss tangent given by σ /ε
See lessω. The loss tangent is used to determine if the material is a conductor or dielectric.
Calculate the frequency at which the conduction and displacement currents become equal with unity conductivity in a material of permittivity 2.
b) 9 GHz Explanation: When Jd = Jc , we get εωE = σE. Thus εo(2∏f) = σ. On substituting conductivity as one and permittivity as 2, we get f = 9GHz.
b) 9 GHz
Explanation: When Jd = Jc , we get εωE = σE. Thus εo(2∏f) = σ. On substituting
See lessconductivity as one and permittivity as 2, we get f = 9GHz.
Find the magnitude of the displacement current density in air at a frequency of 18GHz in frequency domain. Take electric field E as 4 units.
d) 4 Explanation: Jd = dD/dt = εdE/dt in time domain. For frequency domain, convert using Fourier transform, Jd = εjωE. The magnitude of Jd = εωE = ε(2πf)E. On substituting, we get 4 ampere.
d) 4
Explanation: Jd = dD/dt = εdE/dt in time domain. For frequency domain, convert using
See lessFourier transform, Jd = εjωE. The magnitude of
Jd = εωE = ε(2πf)E. On substituting, we get 4 ampere.
Calculate the displacement current density when the electric flux density is 20sin 0.5t.
b) 10cos 0.5t Explanation: The displacement current density is given by, Jd = dD/dt. Jd = d(20sin 0.5t)/dt = 20cos 0.5t (0.5) = 10cos 0.5t.
b) 10cos 0.5t
Explanation: The displacement current density is given by, Jd = dD/dt.
See lessJd = d(20sin 0.5t)/dt = 20cos 0.5t (0.5) = 10cos 0.5t.
Find the conductivity of a material with conduction current density 100 units and electric field of 4 units.
a) 25 Explanation: The conduction current density is given by, Jc = σE. To get conductivity, σ= J/E = 100/4 = 25 units.
a) 25
Explanation: The conduction current density is given by, Jc = σE. To get conductivity, σ= J/E = 100/4 = 25 units.
See lessFind the velocity of an electron when its kinetic energy is equal to one electron volt (in 105m/s). Given charge of an electron e = 1.6 x 10-19 and mass of an electron m = 9.1 x 10- 31 .
c) 5.9 Explanation: When the kinetic energy and one electron volt are equal, we can equate mv2/2 = eV. Put e and m in the equation to get velocity v = 5.9 x 105 m/s.
c) 5.9
Explanation: When the kinetic energy and one electron volt are equal, we can equate
See lessmv2/2 = eV. Put e and m in the equation to get velocity v = 5.9 x 105 m/s.
Find the mean free path of an electron travelling at a speed of 18m/s in 2 seconds.
b) 36 Explanation: The mean free path is defined as the average distance travelled by an electron before collision takes place. It is given by, d = v x τc, where v is the velocity and τc is the collision time. Thus d = 18 x 2 = 36m.
b) 36
Explanation: The mean free path is defined as the average distance travelled by an
See lesselectron before collision takes place. It is given by, d = v x τc, where v is the velocity and τc is the collision time. Thus d = 18 x 2 = 36m.