301. The most important property of magnetic materials is
A) Permeability
B) Resistivity
C) Conductivity
D) Dielectric strength
Ans: A
302. The main source of resistivity in metals is
A) Lattice vibration
B) Electron collisions
C) Impurities
D) All of these
Ans: D
303. A semiconductor device is based on
A) Controlled flow of electrons and holes
B) Ionic conduction
C) Magnetic induction
D) Radiation effect
Ans: A
304. The type of bonding in metals is
A) Metallic
B) Ionic
C) Covalent
D) Hydrogen
Ans: A
305. The most common insulating gas used in high-voltage switchgear is
A) SF₆ (sulphur hexafluoride)
B) Hydrogen
C) Nitrogen
D) Oxygen
Ans: A
306. Ferromagnetic materials have
A) Strong positive susceptibility
B) Weak positive susceptibility
C) Negative susceptibility
D) Zero susceptibility
Ans: A
307. The permeability of diamagnetic materials is
A) Less than one
B) Equal to one
C) Greater than one
D) Infinite
Ans: A
308. The conduction in electrolytes is due to
A) Ions
B) Free electrons
C) Holes
D) None
Ans: A
309. The relative permittivity of air is nearly
A) 1
B) 2
C) 3
D) 4
Ans: A
310. When a dielectric is placed in an electric field, it becomes
A) Polarized
B) Magnetized
C) Ionized
D) Conductive
Ans: A
311. The most suitable material for transformer core is
A) Cold-rolled grain-oriented silicon steel
B) Mild steel
C) Aluminum
D) Ferrite
Ans: A
312. The eddy current loss per unit volume varies as
A) Frequency²
B) Voltage²
C) Current²
D) Frequency
Ans: A
313. Magnetic materials used in relays should have
A) Low hysteresis loss
B) High coercivity
C) High remanence
D) High resistivity
Ans: A
314. In an intrinsic semiconductor, the number of electrons equals
A) Number of holes
B) Twice number of holes
C) Half the number of holes
D) None
Ans: A
315. The unit of magnetization is
A) A/m
B) Wb/m²
C) Tesla
D) H/m
Ans: A
316. The drift velocity of electrons in a conductor is of the order of
A) 10⁻⁴ m/s
B) 10⁻¹ m/s
C) 10 m/s
D) 10³ m/s
Ans: A
317. Ferromagnetic domains are separated by
A) Domain walls
B) Grain boundaries
C) Atomic layers
D) None
Ans: A
318. The Curie point is the temperature at which
A) Ferromagnetic → Paramagnetic
B) Diamagnetic → Paramagnetic
C) Paramagnetic → Ferromagnetic
D) None
Ans: A
319. The loss tangent of a dielectric measures
A) Energy loss
B) Dielectric constant
C) Electric strength
D) Magnetic loss
Ans: A
320. The magnetic field intensity is measured in
A) A/m
B) Wb/m²
C) Tesla
D) Gauss
Ans: A
321. Conductors obeying Ohm’s law are called
A) Ohmic
B) Non-ohmic
C) Linear
D) Ideal
Ans: A
322. The property of a material to retain magnetism after removal of magnetizing force is
A) Retentivity
B) Coercivity
C) Permeability
D) Hysteresis
Ans: A
323. For permanent magnets, a material must have
A) High retentivity and high coercivity
B) Low coercivity
C) Low retentivity
D) Low hysteresis loss
Ans: A
324. In semiconductors, conductivity is due to
A) Charge carriers
B) Lattice
C) Ions
D) All
Ans: A
325. The primary function of the magnetic core in a transformer is
A) Provide low reluctance path
B) Increase resistance
C) Reduce hysteresis
D) Store energy
Ans: A
326. Paramagnetic materials have relative permeability
A) Slightly greater than 1
B) Slightly less than 1
C) Much greater than 1
D) Much less than 1
Ans: A
327. The resistivity of a semiconductor is
A) More than conductor, less than insulator
B) Equal to conductor
C) More than insulator
D) Constant
Ans: A
328. The most common material for thermistors is
A) Metal oxide
B) Copper
C) Graphite
D) Nickel
Ans: A
329. The phenomenon of magnetostriction is utilized in
A) Ultrasonic generators
B) Transformers
C) Relays
D) Meters
Ans: A
330. Dielectric heating is used for
A) Plastic welding
B) Cooking
C) Cooling
D) Magnetizing
Ans: A
331. The drift velocity of charge carriers depends on
A) Electric field
B) Temperature
C) Mobility
D) Both A and C
Ans: D
332. The effect of temperature on resistance of a semiconductor is
A) Resistance decreases
B) Resistance increases
C) Constant
D) Unpredictable
Ans: A
333. The basic mechanism of conduction in metals is
A) Free electron motion
B) Hole motion
C) Ionic conduction
D) Dipole movement
Ans: A
334. A material with low coercivity is used for
A) Transformer cores
B) Permanent magnets
C) Compasses
D) Memory devices
Ans: A
335. The hysteresis loop area represents
A) Energy loss per cycle
B) Magnetic flux
C) Permeability
D) Retentivity
Ans: A
336. The resistance of a metallic conductor increases with
A) Temperature
B) Area
C) Length
D) All of these
Ans: A
337. Insulating materials are chosen for their
A) High resistivity
B) High dielectric strength
C) Low dielectric loss
D) All of these
Ans: D
338. The charge carriers in an N-type semiconductor are
A) Electrons
B) Holes
C) Both
D) Ions
Ans: A
339. The magnetic circuit reluctance is analogous to
A) Electrical resistance
B) Inductance
C) Capacitance
D) None
Ans: A
340. The Fermi level represents
A) Highest occupied energy level at 0 K
B) Lowest level
C) Mid band
D) None
Ans: A
341. Dielectric loss increases with
A) Frequency
B) Temperature
C) Voltage
D) All of these
Ans: D
342. Magnetic materials with small hysteresis loop are suitable for
A) Transformers
B) Permanent magnets
C) Loudspeakers
D) Meters
Ans: A
343. The intrinsic carrier concentration in semiconductors increases with
A) Temperature
B) Pressure
C) Electric field
D) Doping
Ans: A
344. The electric dipole moment is a product of
A) Charge × Distance
B) Voltage × Current
C) Field × Charge
D) None
Ans: A
345. The resistivity of a superconductor below critical temperature is
A) Zero
B) Infinite
C) Constant
D) Decreases slightly
Ans: A
346. Which material is used for brush in DC machines?
A) Carbon
B) Copper
C) Graphite
D) Both A and C
Ans: D
347. The resistivity of germanium is
A) Higher than silicon
B) Lower than silicon
C) Equal to silicon
D) None
Ans: B
348. The direction of magnetic lines of force is from
A) North to South
B) South to North
C) Either way
D) None
Ans: A
349. A semiconductor behaves as conductor when
A) Temperature increases
B) Temperature decreases
C) Doping decreases
D) None
Ans: A
350. The effect opposite to piezoelectric effect is
A) Electrostriction
B) Magnetostriction
C) Thermoelectric
D) Photovoltaic
Ans: A
351. Electrical conductivity of copper decreases when
A) Temperature increases
B) Temperature decreases
C) Remains constant
D) None
Ans: A
352. The magnetic property of a substance is due to
A) Spin of electrons
B) Orbital motion
C) Both A and B
D) None
Ans: C
353. The dielectric constant of vacuum is taken as
A) 1
B) 0
C) 8.85×10⁻¹²
D) 100
Ans: A
354. The Fermi energy depends on
A) Temperature
B) Carrier density
C) Electric field
D) Doping
Ans: B
355. The most suitable insulator for very high frequency is
A) Teflon
B) PVC
C) Paper
D) Mica
Ans: A
356. The mobility of electrons is defined as
A) Drift velocity per unit electric field
B) Electric field per unit drift velocity
C) Charge per voltage
D) Current per resistance
Ans: A
357. A paramagnetic material loses magnetism when
A) Field is removed
B) Temperature rises
C) Both A and B
D) None
Ans: C
358. Copper is refined by
A) Electrolytic refining
B) Zone melting
C) Chemical purification
D) Magnetic separation
Ans: A
359. Electrical steel is used because it reduces
A) Eddy current loss
B) Copper loss
C) Contact resistance
D) Voltage drop
Ans: A
360. Hard magnetic materials have
A) High coercivity
B) Low retentivity
C) Low hysteresis
D) Low resistivity
Ans: A
361. Mica is used as an insulator because of
A) High dielectric strength
B) Heat resistance
C) Flexibility
D) All of these
Ans: D
362. Superconductors expel magnetic fields due to
A) Meissner effect
B) Hall effect
C) Magnetostriction
D) Seebeck effect
Ans: A
363. The Curie point of nickel is approximately
A) 358°C
B) 770°C
C) 100°C
D) 200°C
Ans: A
364. Conductivity of semiconductors depends on
A) Temperature and doping
B) Voltage
C) Pressure
D) All
Ans: A
365. The resistance of pure metals increases almost linearly with
A) Temperature
B) Voltage
C) Current
D) Pressure
Ans: A
366. The dielectric constant of porcelain is approximately
A) 6
B) 12
C) 20
D) 50
Ans: B
367. Electrical resistivity is expressed in
A) Ω·m
B) S/m
C) W/m
D) H/m
Ans: A
368. A good magnetic material should have
A) High permeability
B) Low coercivity
C) High retentivity
D) All of these
Ans: D
369. For electric heating elements, the material should have
A) High resistivity and high melting point
B) Low resistivity
C) Magnetic properties
D) Low melting point
Ans: A
370. The insulating strength of transformer oil is tested by
A) Breakdown voltage test
B) Flash point test
C) Dielectric loss test
D) All
Ans: A
371. Superconductors are used in
A) MRI machines
B) Maglev trains
C) Particle accelerators
D) All of these
Ans: D
372. The unit of magnetic flux is
A) Weber
B) Tesla
C) Henry
D) Farad
Ans: A
373. When magnetic field is applied to a conductor, the potential difference across sides is called
A) Hall effect
B) Seebeck effect
C) Peltier effect
D) Thomson effect
Ans: A
374. High-resistivity alloys are used for
A) Heating elements
B) Resistors
C) Rheostats
D) All
Ans: D
375. Magnetic susceptibility of paramagnetic material decreases with
A) Temperature
B) Pressure
C) Field strength
D) Volume
Ans: A
376. Dielectric strength is measured in
A) kV/mm
B) A/m
C) Wb/m²
D) Ω·m
Ans: A
377. A perfect conductor has
A) Zero electric field inside
B) Infinite resistance
C) Constant potential difference
D) None
Ans: A
378. The relation between current density J and electric field E is
A) J = σE
B) J = E/σ
C) J = ρE
D) None
Ans: A
379. The main advantage of ferrites in transformer cores is
A) Low eddy current loss
B) High strength
C) High weight
D) Low permeability
Ans: A
380. Electrical contacts are made of
A) Silver alloys
B) Aluminum
C) Iron
D) Zinc
Ans: A
381. In dielectric materials, polarization occurs due to
A) Dipole alignment
B) Conduction
C) Ionization
D) None
Ans: A
382. Which of the following materials exhibits hysteresis?
A) Ferromagnetic
B) Paramagnetic
C) Diamagnetic
D) Non-magnetic
Ans: A
383. The resistance of an ideal conductor is
A) Zero
B) Infinity
C) Constant
D) Variable
Ans: A
384. Copper losses in machines vary as
A) Current²
B) Voltage²
C) Frequency
D) None
Ans: A
385. The function of insulation in cables is to
A) Prevent leakage current
B) Increase strength
C) Reduce voltage
D) None
Ans: A
386. Magnetization is proportional to
A) Magnetic field intensity
B) Flux density
C) Current
D) Resistance
Ans: A
387. Electrical energy stored per unit volume in dielectric =
A) ½ εE²
B) εE
C) E²/ρ
D) ½ μH²
Ans: A
388. The energy stored per unit volume in magnetic field =
A) ½ BH
B) BH
C) ½ μH²
D) None
Ans: A
389. The resistivity of metals is minimum at
A) 0 K
B) Room temperature
C) High temperature
D) Melting point
Ans: A
390. The term “anisotropy” refers to
A) Directional dependence of properties
B) Uniform properties
C) Magnetic saturation
D) None
Ans: A
391. The magnetic saturation of iron is around
A) 2 Tesla
B) 1 Tesla
C) 5 Tesla
D) 0.5 Tesla
Ans: A
392. Magnetic hysteresis causes
A) Energy loss
B) Voltage drop
C) Magnetic shielding
D) None
Ans: A
393. Dielectric materials are
A) Insulators
B) Conductors
C) Magnetic
D) None
Ans: A
394. Thermal runaway in semiconductors occurs due to
A) Negative temperature coefficient
B) Positive coefficient
C) Heat sink failure
D) None
Ans: A
395. The process of magnetization is
A) Alignment of domains
B) Formation of dipoles
C) Charge separation
D) None
Ans: A
396. In superconductors, magnetic flux is
A) Expelled
B) Doubled
C) Reduced
D) None
Ans: A
397. Copper is not used for heating element because
A) Low resistivity
B) High melting point
C) High cost
D) All
Ans: A
398. The time lag between magnetization and field is
A) Magnetic hysteresis
B) Eddy current
C) Retentivity
D) Reluctivity
Ans: A
399. The reciprocal of resistivity is
A) Conductivity
B) Susceptibility
C) Permeability
D) Permittivity
Ans: A
400. A material is called isotropic when
A) Properties same in all directions
B) Different in all directions
C) Depends on magnetic field
D) None
Ans: A
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