1. Major constituent of Elektron alloy is ___________
a) Copper
b) Nickel
c) Magnesium
d) Zinc
Explanation: Elektron contains 3-12% aluminum and 2% zinc, 0.03% manganese and rest is magnesium. It is very light alloy and used where weight is the major consideration in design.
2. Which of the following alloy is widely used in thermo couples?
a) Brass
b) Bronze
c) Duralumin
d) Nichrome
Explanation: Nichrome contains 80% Ni and 20% Cr. It is used mostly in thermocouples and in strain gauges.
3. Major constituent of Duralumin alloy is ___________
a) Copper
b) Nickel
c) iron
d) Aluminum
Explanation: Duralumin is the age hardenable alloy of aluminium alloyed mainly with copper and with manganese and magnesium. Being a lightweight alloy, duralumin finds its use widely in aerospace industry.
4. What is the approximate percentage of Lead in soft solder?
a) 60
b) 50
c) 90
d) 99.02
Explanation: Soft solder is the eutectic alloy of 50% Pb and 50% Sn, having a melting point of 450oC.
5. Which of the following is the de Broglie’s equation (λ = wavelength, v = velocity, m = mass, h = Planck’s constant)?
a) λ = h/mv
b) λ = h/m
c) λ = h/v
d) λ = mv/h
Explanation: The equation, λ = h/mv is known as de Broglie’s equation. This equation represents the wave-particle duality of an electron.
6. With an increase in the mean free path of electrons, materials conductivity ____________
a) increases
b) decreases
c) remains constant
d) first increases and then decreases
Explanation: Conductivity of a material increases with an increase in the mean free path of electrons. Mean free path is nothing but the average distance travelled by an electron between two successive collisions
7. What is the resistivity of silver (in Ohm-m) at room temperature?
a) 1.59 × 10-2
b) 1.59 × 10-3
c) 1.59 × 10-5
d) 1.59 × 10-9
Explanation: Silver has lowest conductivity. The resistivity of silver is 1.59 × 10-9 Ω-m.
8. What is the resistivity of iron (in Ohm-m) at room temperature?
a) 9.71 × 10-2
b) 9.71 × 10-8
c) 9.71 × 10-5
d) 9.71 × 10-9
Explanation: Iron has medium conductivity. The resistivity of iron is 9.71 × 10-8 Ω-m.
9. What is the resistivity of bismuth (in Ohm-m) at room temperature?
a) 1.29 × 10-6
b) 1.29 × 10-3
c) 1.29 × 10-5
d) 1.29 × 10-9
Explanation: Bismuth has low conductivity. The resistivity of iron is 1.29 × 10-6 Ω-m.
10. What is the energy gap (Eg) of an insulator?
a) Eg < 3 ev
b) Eg < 1 ev
c) Eg < 0 ev
d) Eg > 3 ev
Explanation: The energy gap (Eg) of an insulator is approximately equal to 15 ev.