All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 103 of 158
2041. A good electric contact material should have all of the following properties except_____________?
- A. high resistivity
- B. high resistance to corrosion
- C. good thermal conductivity
- D. high melting point
Explanation: A good electrical contact should have low resistivity so that it produces little voltage drop and heating.
Correct answer: high resistivity- A. Glass
- B. Quartz
- C. Corrundum
- D. Neoprene
Explanation: Quartz is a classic piezoelectric material: mechanical stress on it produces charge, and an applied voltage causes mechanical deformation.
Correct answer: Quartz- A. resonant waves
- B. musical waves
- C. microwaves
- D. ultrasonic waves
Explanation: Piezoelectric crystals convert electrical energy into mechanical vibrations and are commonly driven at high frequency to generate…
Correct answer: ultrasonic waves- A. Cast-iron
- B. Graphite
- C. Rubber
- D. Glass
Explanation: Rubber is viscoelastic, so it shows both elastic recovery and time-dependent viscous deformation.
Correct answer: Rubber- A. copper and aluminium
- B. tin and lead
- C. nickel, copper and zinc
- D. silver, copper and lead
Explanation: Traditional solder is a low-melting alloy of tin and lead, allowing components and wires to be joined without melting the base metals.
Correct answer: tin and lead- A. GLS lamps
- B. electric arc furnace
- C. dry cells
- D. cinema projectors
Explanation: Carbon electrodes are used in arc furnaces, dry-cell batteries, and carbon-arc cinema projectors.
Correct answer: GLS lamps- A. Silver nitrate
- B. Ferric oxide
- C. Small particles of iron
- D. Silicon-iron
Explanation: Magnetic recording tape is coated with fine ferric oxide particles, which retain magnetisation corresponding to the recorded signal.
Correct answer: Ferric oxide- A. Fe203
- B. Si02
- C. AI2O3
- D. B2O3
Explanation: Silica, SiO₂, forms the principal glass-forming material and gives ordinary glass its rigid network.
Correct answer: Si02- A. Induction hardened copper
- B. Hard drawn copper
- C. Pure annealed copper
- D. Copper containing traces of silicon
Explanation: Pure annealed copper has the highest conductivity because it contains very few resistivity-increasing impurities and has a soft…
Correct answer: Pure annealed copper- A. Carbon
- B. Steel
- C. Silver
- D. Aluminium
Explanation: Among these choices, carbon has the greatest electrical resistivity, whereas silver is the best conductor and aluminium is also highly…
Correct answer: Carbon- A. silver and tin
- B. copper and tungsten
- C. tungsten and silver
- D. copper and nickel
Explanation: Constantan is a copper-nickel alloy, commonly containing roughly 55% copper and 45% nickel.
Correct answer: copper and nickel- A. critical magnetic field
- B. transition temperature
- C. critical current density
- D. none of the above
Explanation: Critical current density depends strongly on the material's structure, including defects, grain boundaries, and geometry, so it is…
Correct answer: critical current density- A. 18.0°K
- B. 9.22°K
- C. 4.12°K
- D. 1.14'K
Explanation: Mercury becomes superconducting at approximately 4.12 K, its transition temperature.
Correct answer: 4.12°K- A. zero
- B. negative real value
- C. positive real value
- D. complex value
Explanation: The critical magnetic field falls to zero at the transition temperature because the material loses superconductivity at that point.
Correct answer: zero2055. By increasing impurity content in the metal alloy the residual resistivity always_____________?
- A. decreases
- B. increases
- C. remains constant
- D. becomes temperature independent
Explanation: Impurity atoms disturb the regular lattice and scatter conduction electrons, increasing residual resistivity.
Correct answer: increases- A. electric field
- B. magnetic field
- C. electromagnetic field
- D. none of the above
Explanation: An electric field exerts force on free electrons and produces their directed drift, which is the basis of conduction current.
Correct answer: electric field- A. a liquid
- B. a metal
- C. a metal liquid
- D. a gas
Explanation: Mercury is a metal that is liquid at ordinary room temperature, so it is commonly described as a liquid metal.
Correct answer: a metal liquid- A. infrared frequencies
- B. d.c. and low frequency
- C. a.c. and high frequency
- D. frequencies having no effect
- E. none of the above
Explanation: Superconductivity is most practically observed with direct current and at low frequencies, where AC losses remain small.
Correct answer: d.c. and low frequency- A. precision instruments
- B. heating elements
- C. motor starters
- D. incandescent lamps
- E. all of the above
Explanation: High-resistivity materials limit current and dissipate power, so they are used in precision resistors, heating elements, motor-starter…
Correct answer: all of the above- A. magnetic field strength
- B. temperature
- C. either (A) or (B)
- D. both (A) and (B)
Explanation: The critical current density of a superconductor varies with both temperature and applied magnetic-field strength, generally decreasing as…
Correct answer: both (A) and (B)