Electrical Engineering · Question Bank

Magnetic Circuits

84 questions · page 3 of 5. Answer in your head first, then check the solution.

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TypeAll 84Problem solving 28Objective 56
DifficultyAll 84Easy 78Medium 5Hard 1
#41📜 EE Pre-Board August 2017📘 PowerhouseEasy
It is difficult to magnetize steel because of its
Ahigh permeability
Bhigh conductivity
Clow permeability
Dlow retentivity
#42📜 EE Pre-Board August 2017📘 PowerhouseEasy
The reciprocal of permeability is
Areluctance
Bpermittivity
Creluctivity
Dconductivity
#43📜 EE Pre-Board August 2017📘 PowerhouseEasy
Two conductors carrying 50 amperes and 75 amperes respectively are placed 10 cm apart. Calculate the force between them per meter.
A0.075 N/m
B0.0375 N/m
C0.0075 N/m
D0.00375 N/m
#44📜 EE Pre-Board August 2017📘 PowerhouseEasy
Calculate the AT/m needed to produce a flux density of 0.001 Wb/m² at the center of a long straight solenoid.
A0.796
B79.6
C7,958
D796
#45📜 EE Pre-Board August 2017📘 PowerhouseMedium
An air core toroidal coil has 120 turns and a length of 12 cm. What current is required to set up a flux of \(1.2 \times 10^{-6}\) weber if the cross-sectional area is 12 square cm?
A7.96 A
B0.796 A
C0.0796 A
D1.59 A
#46📜 EE Pre-Board August 2017📘 PowerhouseEasy
A straight conductor 100 cm long and carrying 40 A lies perpendicular to a magnetic field of 1.5 T. What is the mechanical power in watts required to move the conductor at a uniform speed of 5 meters per second?
A60 W
B7.5 W
C200 W
D300 W
#47📜 EE Pre-Board March 2018📘 PowerhouseEasy
Which does not belong
Alines per square centimeter
Bmaxwells per square centimeter
Cflux
Dgauss
#48📜 EE Pre-Board March 2018📘 PowerhouseEasy
A magnetizing force of 1000 AT/m will produce a flux density of ___________ in air
A1.257 mWb/m²
B0.63 mWb/m²
C1.257 Wb/m²
D0.63 Wb/m²
#49📜 EE Pre-Board August 2018📘 PowerhouseEasy
Two similar poles, each of 1 Wb, placed 1 m apart in air will experience a repulsive force of _____.
A63,000 N
B796 N
C\(8 \times 10^{12}\) N
D\(63 \times 10^{-3}\) N
#50📘 EE Pocket Reviewer RojasEasy
Which of the following applications requires magnetic materials with large hysteresis loop?
ADC generators
BAC motors
CTransformers
DPermanent magnets
#51📘 EE Pocket Reviewer RojasEasy
Which one is considered an advantage of using air as the core for inductors?
AIt has excellent efficiency
BIt has high permeability
CIt allows high inductance to exist in a small volume
DIt has high permeability that can vary over a wide range
#52📘 EE Pocket Reviewer RojasEasy
The force of attraction or repulsion between two poles is inversely proportional to the square of the distance between them. What is the name of this law?
ACoulomb’s first law
BLenz law
CFaraday’s electromagnetic induction law
DCoulomb’s second law
#53📘 EE Pocket Reviewer RojasEasy
What do you mean by “degaussing”?
AAdding magnetic particles on a magnet
BCleaning a magnet from dirt
CDemagnetize a metal
DRestoring the magnetic strength of a magnet
#54📘 EE Pocket Reviewer RojasEasy
Let: B = flux density and H = magnetic field intensity. Hysteresis is a phenomenon where
AB lags behind H.
BB leads ahead of H
CB and H are in-phase
DEither A or B only
#55📘 EE Pocket Reviewer RojasEasy
Temporary magnet is found in which of the following applications?
AElectrical instruments
BLoud speakers
CEarphones
DMotors
#56📘 EE Pocket Reviewer RojasEasy
What is the reason why steel is hard to magnetize?
AIts permeability is low
BIts permeability is high
CIts reluctance is low
DIts retentivity is high
#57📘 EE Pocket Reviewer RojasEasy
What is the purpose of placing a ferromagnetic core in an inductor?
ATo limit the current
BTo reduce the inductance
CTo increase the inductance
DTo increase the current carrying capacity
#58📘 EE Pocket Reviewer RojasEasy
Which one is a ferromagnetic material?
ALead
BBismuth
CIron
DWater
#59📘 EE Pocket Reviewer RojasEasy
The cores of magnetic devices use materials having which of the following characteristics?
AIts permeability must be low
BIts permeability must be high
CIts permeability must be close to zero
DIts permeability must not be too low but not too high also
#60📘 EE Pocket Reviewer RojasEasy
What is the SI unit of flux density?
AWeber/meter
BAmpere-turn per meter
CTesla
DNewton per weber

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