Basic Electrical Engineering MCQ_68_1(Electromagnetism)


Q.196 _______ is state that The mmf around a closed path is equal to the current enclosed by the path.
    A. Maxwell’s law
    B. Ampere’s work law
    C. Ampere’s circuital law
    D. Both A and C
Ans.: D
Q.197 Work law is applicable to all ______ whatever the shape of closing path.
    A. electric field
    B. magnetic field
    C. electrostatic field
    D. all of the above
Ans.: B
Q.198 Ampere’s circuital law is used for obtaining the value of the magneto motive force around___
    A. a long straight current carrying conductor
    B. a long solenoid
    C. Both A and B
    D. coil
Ans.: C
Q.199 What are the applications of Biot- Savart’s law?
    A. Magnetic field strength due a finite length of wire currying current
    B. Magnetic field strength along Axis of a square coil
    C. Magnetizing force on the Axis of a circular coil and on the axis of a short solenoid
    D. All of the above
Ans.: D
Q.200 A wire of 2.5 m Long is bent into a circle. If the current flowing through the wire is 100A, find the magnetizing force at the centre of circle.
    A. 125.6AT/m
    B. 136AT/m
    C. 120.5AT/m
    D. 124.5AT/m
Ans.: D
Q.201 Find the magnitude of force between two infinite parallel conductors carrying currents of 10Amp each and distance between them is 20cm.
    A. 10-10N
    B. 10-4N
    C. 10-8N
    D. 10-6N
Ans.: B
Q.202 One ampere current as that current which when flowing in each of the two infinitely long parallel conductors situated in vacuum and separated 1 meter between centers, produces on each conductor a force of _____ N per meter length.
    A. 2 x10-7
    B. 2 x10-8
    C. 2 x10-6
    D. 2 x10-9
Ans.: A
Q.203 A laminated soft iron ring of relative permeability 1000 has a mean circumference of 800 mm and a cross sectional area 500 cm2. A radial air gap of 1 mm width is cut in the ring which is wound 1000 turns. Calculate the current required to produce an air gap flux of 0.5 mWeb if leakage factor is 1.2 and stacking factor 0.9.
    A. 1.54 A
    B. 1.64 A
    C. 1.74 A
    D. 1.44 A
Ans.: B
Q.204 A circuit has 1000 turns enclosing a magnetic circuit 20 cm2 in section. With 4A, flux density of 1.0 Wb/m2 and with 9A, it is 1.4 Wbm2. Find the mean value of the inductance between these current limits and the induced emf if the current falls from 9 to 4A in 0.05 sec.
    A. 1.6 H and 16 V
    B. 16 H and 1.6 V
    C. 0.16 H and 16 V
    D. 16 V and 0.16 H
Ans.: C
Q.205 A coil of 1000 turns is wound on a torroidal magnetic core having a reluctance of 104 AT/Wb. Determine energy stored in the magnetic circuit if coil current is 5A and is increasing at the rate of 200 A/s.
    A. 125J
    B.12.5 J
    C.1.25J
    D.0.125J
Ans.: B
Q.206 When two coils are said to have a mutual inductance of one Henry?
A. current changing at the rate of 10 amp/sec in one coil induces an emf of one volt in the other.
B. current changing at the rate of 10 amp/sec in one coil induces an emf of one volt in the other.
C. current changing at the rate of 1 amp/sec in one coil induces an emf of one volt in the other.
D. current changing at the rate of 1 amp/sec in one coil induces an emf of 10 volt in the other.
Ans.: C
Q.207 Two coils A of 12500 turns and B of 16000 turns, lie in parallel planes so that 60 % of flux produced in A links coil B. It is found that a current of 5A in A produces a flux of 0.6 mwb while the same current in B produces 0.8 mWb. Determine coupling coefficient.
    A. 0.586
    B. 0.866
    C. 0.686
    D. 0.486
Ans.: A
Q.208 calculate the hourly loss of energy in kWh in a specimen of iron, the hysteresis loop of which is equivalent in area to 250 J/m. frequency 50Hz; specific gravity of iron 7.5; weight of specimen 10 kg.
    A. 2.78 x 10-5 kWh
    B. 27.8 x 10-5 kWh
    C. 278 x 10-5 kWh
    D. 27.8 x 10-6 kWh
Ans.: B
Q.209 when two coils are said to have a mutual inductance of one henry?
    A. Ten ampere current when flowing in one coil produces flux linkage of one wb-turn in the other
    B. one ampere current when flowing in one coil produces flux linkage of ten wb-turn in the other
    C. one ampere current when flowing in one coil produces flux linkage of infinite wb-turn in the other
    D. one ampere current when flowing in one coil produces flux linkage of one wb-turn in the other
Ans.: D
Q.210 Coefficient of mutual inductance between two coils is defined as:
    A. the weber turns in one coil due to one ampere current in the other
    B. the weber turns in one coil only
    C. one ampere current in only coil
    D. none of the above
Ans.: A

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