Material Science - Oxidation and Corrosion

1. Which one is the wrong anode-cathode combination
(a) Zinc-Iron
(b) Nickel-Titanium
(c) Iron-Tin
(d) Silver-zinc

2. The metals which do not form adherent oxide film on surface are
(a) Gold and Silver
(b) Iron and Steel
(c) Copper and Aluminium
(d) Nickel and Titanium

3. Which of the following elements added to iron to improve its oxidation resistance
(a) Zinc
(b) Magnesium
(c) Chromium and aluminium
(d) None of the above

4. The corrosion by the mechanism of oxygen absorption can occur if
(a) Electrolyte is neutral or alkaline
(b) Electrolyte is neutral or acidic
(c) Electrolyte is neither neutral and nor acidic
(d) None of the above

5. In order to form a protective oxide layer, the ratio of the volume of oxide formed to that of metal consumed should be
(a) greater than one
(b) less than one
(c) much greater than one
(d) none of the above

6. The potential of a galvanic cell of copper (potential of +0.34 Volt) and aluminium (potential of –1.66 Volt) is
(a) +1.5 Volt
(b) +1.66 Volt
(c) –1.32 V
(d) +2 Volt

7. In the corrosion process by evolution of hydrogen
(a) the cathodes have larger area than anodes
(b) the anodes have larger area than cathodes
(c) the areas of anodes and cathodes are same
(d) none of the above

8. The highest percentage of chromium that can be added to steel is usually
(a) 25
(b) 18
(c) 15
(d) 10

9. Carbon percentage in cutley steel is
(a) 1.35 to 1.65
(b) 0.76 to 0.80
(c) 0.25 to 0.30
(d) 0.5 to 1.0

10. The stainless steels owe their resistance to the presence of
(a) Carbon
(b) Sulphur
(c) Manganese
(d) Chromium


Answers

    1. (d)    2. (a)    3. (c)    4. (a)    5. (a)
    6. (d)    7. (b)    8. (b)    9. (c)    10. (d)

Comments

Post a Comment

Popular posts from this blog

Electrical Machines (Three Phase Transformers)

1. Which of the following connections is best suited for 3-phase, 4-wire service ? (a) Δ − Δ (b) Y − Y (c) Δ − Y (d) Y − Δ 2. In a three-phase Y-Y transformer connection, neutral is fundamental to the (a) suppression of harmonics (b) passage of unbalanced currents due to unbalanced loads (c) provision of dual electric service (d) balancing of phase voltages with respect to line voltages. 3. As compared to Δ − Δ bank, the capacity of the V − V bank of transformers is ......... percent. (a) 57.7 (b) 66.7 (c) 50 (d) 86.6 4. If three transformers in a Δ − Δ are delivering their rated load and one transformer is removed, then overload on each of the remaining transformers is ......... percent. (a) 66.7 (b) 173.2 (c) 73.2 (d) 58 5. When a V − V system is converted into a Δ − Δ system, increase in capacity of the system is ......... percent. (a) 86.6 (b) 66.7 (c) 73.2 (d) 50 6. For supplying a balanced 3 − φ load of 40-kVA, rating o
Read more

Thermodynamics (Compressible Flow)

1. All real fluids are (a) incompressible (b) compressible to some extent (c) compressible to any extent (d) none of the above. 2. A change in the state of a system at constant volume is called (a) isobaric process (b) isochoric process (c) isothermal process (d) adiabatic process. 3. A process during which no heat is transferred to or from the gas is called an (a) isochoric process (b) isobaric process (c) adiabatic process (d) isothermal process. 4. The sonic velocity is largest in which of the following ? (a) Water (b) Steel (c) Kerosene (d) Air. 5. An isentropic flow is one which is (a) isothermal (b) adiabatic (c) adiabatic and irreversible (d) adiabatic and reversible. 6. Indica upto what Mach number can a fluid flow be considered incompressible ? (a) 0.1 (b) 0.3 (c) 0.8 (d) 1.0. 7. Which of the following is the basic equation of compressible fluid flow ? (a) Continuity equation (b) Momentum equation (c) Energy equation (d) Equation of st
Read more

Electrical Machines (Special Machines)

1. A single-stack, 4-phase, 6-pole VR stepper motor will have a step angle of (a) 15º (b) 30º (c) 45º (d) 90º 2. In a three-stack 12/8-pole VR motor, the rotor pole pitch is (a) 15º (b) 30º (c) 45º (d) 60º 3. A three-stack VR stepper motor has a step angle of 10º. What is the number of rotor teeth in each stack ? (a) 36 (b) 24 (c) 18 (d) 12 4. If a hybrid stepper motor has a rotor pitch of 36º and a step angle of 9º, the number of its phases must be (a) 4 (b) 2 (c) 3 (d) 6 5. What is the step angle of a permanent-magnet stepper motor having 8 stator poles and 4 rotor poles ? (a) 60º (b) 45º (c) 30º (d) 15º 6. A stepping motor is a .................. device. (a) mechanical (b) electrical (c) analogue (d) incremental 7. Operation of stepping motors at high speeds is referred to as (a) fast forward (b) slewing (c) inching (d) jogging 8. Which of the following phase switching sequence represents half-step operation of a VR stepper motor ? (a) A
Read more