The force between two parallel currents is
A Always repulsive
B Always attractive
C Attractive if currents are in same direction
D Attractive only if currents differ
Magnetic field intensity inside a long solenoid is independent of
A Number of turns
B Current
C Length
D Radius
A current loop behaves like
A An electric dipole
B A magnetic dipole
C A capacitor
D A dielectric
Magnetic field inside a toroid is
A Zero at center
B Maximum outside
C Contained within the core
D Uniform everywhere
Gauss’s law for magnetism is written as
A ∇⋅B = ρ
B ∇⋅B = 0
C ∇×B = 0
D ∇⋅E = 0
Magnetic flux through a surface is
A Scalar
B Vector
C Always zero
D Tensor
The Hall field is produced due to
A Electric field only
B Magnetic field only
C Lorentz force on moving charges
D Thermal motion
Hall coefficient of a semiconductor can be
A Only positive
B Only negative
C Positive or negative
D Only zero
Carrier mobility can be calculated using
A RH = nq
B μ = σRH
C μ = IR
D μ = 1/σ
Diamagnetism exists due to
A Spin alignment
B Orbital motion of electrons
C Domain formation
D Magnetic dipoles
Curie’s law relates
A χ ∝ T
B χ ∝ 1/T
C χ ∝ T²
D χ independent of T
Ferromagnetic domains disappear at
A Debye temperature
B Curie temperature
C Melting temperature
D Superconducting temperature
A soft magnetic material has
A High coercivity
B Low coercivity
C Large hysteresis loop
D Very high remanence
Faraday’s law can be expressed using which Maxwell equation?
A ∇×E = −∂B/∂t
B ∇⋅E = 0
C ∇⋅B = 0
D ∇×B = μ0J
Induced EMF in a coil depends on
A Rate of change of flux
B Flux only
C Coil material
D Resistance only
Increasing the number of turns in a coil will
A Decrease EMF
B Increase EMF
C Make EMF zero
D Not affect EMF
Self-inductance of a coil is proportional to
A N
B N²
C 1/N
D √N
A conductor moving parallel to magnetic field lines experiences
A Maximum EMF
B Zero EMF
C Minimum EMF
D Increasing EMF
Lenz’s law is a consequence of
A Coulomb’s law
B Newton’s third law
C Conservation of energy
D Conservation of charge
The induced electric field due to changing magnetic flux is
A Conservative
B Non-conservative
C Always zero
D Infinite
In a transformer, eddy current losses are reduced by
A Thick plates
B Laminated core
C Decreasing frequency
D Increasing flux
AC current in a capacitor leads voltage by
A 90°
B 45°
C 0°
D 180°
In a series LCR circuit at resonance
A Current is minimum
B Voltage is maximum
C Impedance is purely resistive
D Reactance is maximum
Quality factor Q is
A ω0L/R
B R/ω0L
C RC
D None
Skin effect is prominent at
A Low frequencies
B High frequencies
C DC only
D Zero frequency
Skin depth is inversely proportional to
A √frequency
B frequency
C conductivity
D both √frequency and √conductivity
Displacement current exists
A Only in dielectrics
B Only in conductors
C In vacuum or any region with changing electric field
D Only in metals
Maxwell’s equations are
A Two equations
B Three equations
C Four equations
D Five equations
Light is
A A longitudinal wave
B A transverse EM wave
C A mechanical wave
D A scalar wave
EM waves travel fastest in
A Water
B Glass
C Air
D Vacuum
In EM waves, E and B are always
A Parallel
B Perpendicular to each other
C Opposite
D Random
Energy in EM waves is carried by
A Electric field only
B Magnetic field only
C Both E and B
D Neither
Poynting vector direction indicates
A Electric flux
B Magnetic flux
C Energy flow
D Charge density
Poynting vector is given by
A E + B
B E × B / μ
C E × H
D EB
Wave impedance in free space is approximately
A 50 Ω
B 75 Ω
C 200 Ω
D 377 Ω
Attenuation of EM waves in conductors is due to
A Dielectric loss
B Electron inertia
C Ohmic loss
D None
In good conductors, phase difference between fields is
A 0°
B 45°
C 90°
D 180°
Anomalous dispersion occurs when
A n increases with frequency
B n decreases with frequency
C n constant
D Frequency is zero
Wave equation for magnetic field is
A ∇²B = μϵ ∂²B/∂t²
B ∇⋅B = 0
C ∇×B = 0
D None
The velocity of EM waves in a medium is
A 1/μϵ
B 1/√(μϵ)
C √(μϵ)
D Infinite
The refractive index of a medium for EM waves is
A √(μϵ)
B ϵ/μ
C √(ϵr μr)
D ϵ0/μ0
A perfect conductor reflects
A All EM waves
B No EM waves
C Only low-frequency waves
D Only high-frequency waves
EM waves carry
A Momentum
B Mass
C Charge
D Spin only
A photon’s momentum is
A mc
B 0
C hν
D h/λ
Photon momentum p = h/λ.
Conductivity affects
A Attenuation
B Skin depth
C Wave propagation
D All of these
An EM wave is attenuated in conductors because
A B decreases
B E decreases
C Both decay exponentially
D None
In dispersive media
A All frequencies travel at same speed
B Group velocity ≠ phase velocity
C No dependence on ω
D EM waves vanish
For low-loss dielectrics, wave propagation is
A Strongly attenuated
B Nearly unaffected
C Increasing in amplitude
D Impossible
In a capacitor, displacement current flows due to
A Charges moving across plates
B Changing electric field between plates
C Free electrons flowing
D Zero potential
Maxwell predicted EM waves travel at
A 1/√(μ0ϵ0)
B μ0ϵ0
C c/2
D √(μ0/ε0)