1. Which of the following matching is incorrect:
a)Ampere’s circuital law → ∇× H = J + ∂D / ∂t
b) Displacement current density → J = ∂D / ∂ t
c) Poisson’s equation → ∇ 2V = 0
d) Continuity equation → ∇ ⋅ J = − ∂ρ/ ∂ t
Ans: c
2.A loop is rotating about y-axis in a magnetic field B =B0 sinmt ax Wb/m2 . The voltage induced in the loop is due to
a) Motional emf
b) Transformer emf
c) A combination of motional & transformer emf
d) None of the above ax Wb/m2 . The voltage
Ans: c
3.Point charges 30 nC, –20 nC and 10 nC are located at (–1, 0, 2), (0, 0,0) and (1, 5, –1) respectively. The total flux leaving a cube of side 6m centered at the origin is
a) –20 nC
b) 20 nC
c) 10 nC
d)30 nc
Ans: c
4.The equation ∇ × E = −∂B/∂t is the generalization of
a) Amperes Law
b) Faraday Law
c) Gauss’s Law
d) Biot-Saverts Law
Ans: b
5.Reciprocal of reluctance is
a)Henry/meter
b) Henry
c) meter/Henry
d)
Ans: b
6.Which one of the following is correct?
a)∇⋅E = ρv
b) ∇ ⋅ E = ρv /∈o
c) ∇ ⋅ E = −ρv
d) ∇ ⋅ E =∈o ρv
Ans: b
7.Poynting vector gives
a)rate of energy flow.
b) direction of polarization.
c) intensity of electric field.
d) intensity of magnetic field.
Ans: a
8.Plane y=0 carries a uniform current density of 30 az mA/m. At (1, 10, –2), the magnetic field intensity is
a)–15 ax mA/m
b) 15 ax mA/m
c) 477.5 ay μA/m
d) 18.85 ay nA/m
Ans: a
9.Tesla is a unit of
a) field strength
b) inductance
c) flux density
d) flux
Ans: c
10.A permeable substance is one
a) which is a good conductor
b) which is a bad conductor
c) which is a strong magnet
d) through which the magnetic lines of force can pass very easily
Ans: d
11.Ferrites are materials.
a) paramagnetic
b) diamagnetic
c) ferromagnetic
d) none of the above
Ans: c
12.The direction of magnetic lines of force is
a) from south pole to north pole
b) from north pole to south pole
c) from one end of the magnet to another
d) none of the above
Ans: b
13.A material which is slightly repelled by a magnetic field is known as
a) ferromagnetic material
b) diamagnetic material
c) paramagnetic material
d) conducting material
Ans: b
14.A quantitative relation between induced emf and rate of change of flux linkage is known as
a) Maxwell’s law
b) Stroke’s law
c) Lenz’s law
d) Faraday’s law
Ans: d
15.The ratio of intensity of magnetisation to the magnetisation force is known as
a) flux density
b) susceptibility
c) relative permeability
d) none of the above
Ans: b
16. A conductor of length L has current I passing through it, when it is placed parallel to a magnetic field. The force experienced by the conductor
will be
(a) zero
(b) BLI
(c)B/LI
(d) BI/L
Ans: a
17. The force between two long parallel conductors is inversely proportional to
(a) radius of conductors
(b) current in one conductor
(c) product of current in two conductors
(d) distance between the conductors
Ans: d
18. In the left hand rule, forefinger always represents
(a) voltage
(b) current
(c) magnetic field
(d) direction of force on the conductor
Ans: c
19. The electromagnet has 50 turns and a current of 1A flows through the coil. If the length of the magnet circuit is 200 mm, what is the magnetic field strength ?
(a) 2500 AT/m
(b) 250 AT/m
(c) 25 AT/m
(d) 2.5 AT/m
Ans: b
20.The magnetic reluctance of a material
(a) decreases with increasing cross sectional area of material
(6) increases with increasing cross-sec-tional area of material
(c) does not vary with increasing cross-sectional area of material
(d) any of the above
Ans: a
21.For which of the following materials the net magnetic moment should be zero ?
(a) Diamagnetic materials
(b) Ferrimagnetic materials
(c) Antiferromagnetic materials
(d) Antiferrimagnetic materials
Ans: c
22. The magnetism of a magnet can be destroyed by
(a) heating
(b) hammering
(c) by inductive action of another magnet
(d) by all the above methods
Ans: d
23. Those materials are well suited for making permanent magnets which have _____ retentivity and _______ coercivity.
(a) low, high
(b) high, high
(c) high, low
(d) low, low
Ans: b
24. Those magnetic materials are best suited for making armature and transformer cores which have____permeability and_______hystersis
loss.
(a) high, high
(b) low, high
(c) high, low
(d) low, low
Ans: c
25.The unit of magnetic flux is
(a) henry
(b) weber
(c) ampereturn/weber
(d) ampere/metre
Ans: b
26.The Unit of flux is the same as that of
a)Reluctance
b)Resistance
c)Permeance
d)Pole strength
Ans: b
27.The ratio of conduction current density to the displacement current density
a)σ/ jω∈
b)Jσ/ ω∈
c)σω /j∈
d)σ ∈/ jω
Ans: a
28.The charge build up in the capacitor is due to which quantity?
a) Conduction current
b) Displacement current
c) Convection current
d) Direct current
Ans: b
29.Ampere law states that,
a) Divergence of H is same as the flux
b) Curl of D is same as the current
c) Divergence of E is zero
d) Curl of H is same as the current density
Ans: d
30.Electric flux (ΦE),is a _____ field, and its density D, is a ____field
a) Scalar and vector
b) Vector and scalar
c) Vector and vector
d) Scalar and scalar
Ans: a
31.The force on a current-carrying conductor in a magnetic field
depend upon
a)The flux density of the field
b)The strength of the current
c)The length of the conductor perpendicular to the magnetic field
d)The direction of the field and the current
(A)a, b, c only
(B) c, d, a only
(C) a, b, c, and d
(D) b, c, d only
Ans: C
32. Find electric field intensity at (0,3,4)m in Cartesian coordinates due to a point charge Q=0.5uC at the origin
a) 180 V/m
b) 180 V/m
c) 18 V/m
d) 18 V/m
Ans: a
35. Electric field intensity, E ,due to Q is:
a) F/Q
b) F+Q
c) Q/F
d) F×Q
Ans: a
36.One volt of electric potential is equivalent of:
a)1 J/C
b)1 C/J
c)1 A/C
d)1 C/S
Ans: a
37.Three point charges Q1=30 nC, Q2=150 nC, and Q3= -70 nC, are enclosed by surface S. what net flux crosses S
A)180nC
B)110nC
C)100nC
D)0 C
Ans: b
38.Which of the following law states that “the total flux out of a closed surface is equal to the net charges within the surface”?
a)Gaussian’s law
b)Coulomb law
c) Laplace’s law
d)Gauss law
Ans: d
39. Choose the wrong statement with respect to coulomb’s law, the force between two charges Q1 and Q2 is
a)Inversely proportional to the square of the distance
b)Directly proportional to Q2
c)Directly proportional to the distance
d)Directly proportional to Q1
Ans: c
40.The relation between electric flux density D and Electric field intensity is given as:
a) D=ɛE
b) E=ɛD
c) ɛ= E×D
d) E=D
Ans: a
41.Find the expression for the electric field at P (x,y,z) due to a point charge Q at the origin.
a)
b)
c)
d)
Ans: a
42.The magnitude of flux in a magnetic circuit may be calculated as:
a)
b)
c)
d)
Ans: a
43. Out of the given units is for magnetic field intensity, H?
a) AT/m
b)ATm
c) Am
d) AT/m2
Ans: a
44.The gradient is a _____defined for each point in a____field
a)Vector and scalar
b)Vector and vector
c) Scalar and Scalar
d) Scalar and Vector
Ans: a
45.SI unit of magneto motive force(mmf) is:
a)AT
b)AWb/T
c)Wb/AT
d)AT/Wb
Ans: a
46. Which one of the following is the correct statement? Equipotential lines and field lines
a)Are parallel
b)Are anti-parallel
c)Are orthogonal
d)Bear no definite relationship
Ans: c
47.Two charges are placed at a distance apart. Now, if a glass slab is inserted between them, then the force between the charges will
a)Reduce to zero
b)Increases
c)Decrease
d)Not change
Ans: c
48.If a vector field B is solenoidal, which of these is true?
a) Then its curl is zero
b) Then its divergence is zero
c) Both are true
d) None
Ans: b
49. Which of the following is zero as applied to electromagnetic fields?
a)Grad div A
b) Div grad V
c) Div curl A
d) Curl curl A
Ans: c
50.∇×H=J is a differential form of
a)Gauss’s law
b) Ampere’s circuital law
c)Poisson’s equation
d)Laplace’s equation
Ans: a
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– Steve Jobs
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