BE (First/Second) Semester Exam
(Common to all Branches)
Time: 3 hrs
Maximum Marks: 100
Maximum Marks: 100
Minimum Marks: 35
Note: Attempt FIVE questions. All questions carry equal marks and internal choice. Assume suitable data if required.
Unit-I
1. Discuss the composition, specific properties and main applications of the following materials: a) Mild steel (Low carbon steel) (b) High carbon steel (c) High speed steel (d) Stainless steel. 5 each (20 marks)
Ans: Mild steel and High Carbon steel- Refer Page 4 of BME - Basant Agrawal, Wiley India
High speed steel and Stainless steel- Refer Page 6 of BME - Basant Agrawal, Wiley India
Or
Describe the mechanical properties of materials: (a) Tensile strength (tensile stress) (b) Hardness (c) Fatigue strength (d) Modulus of elasticity (e) Toughness. 4 each (20 marks)
Ans: Tensile strength- Page 14 of BME - Basant Agrawal, Wiley India
Hardness and toughness- Page 12 of BME - Basant Agrawal, Wiley India
Fatigue strength- Page 13 of BME - Basant Agrawal, Wiley India
Modulus of elasticity- Page 18 of BME - Basant Agrawal, Wiley India
Unit-II
2. Explain the following properties of any measuring instruments: (a) Hysteresis (b) Sensitivity (c) Response time (d) Precision and accuracy. 5 each (20 marks)
Ans: Precision and acuracy- Page 78 of BME - Basant Agrawal, Wiley India
Or
With the help of a simple diagram explain various parts of a lathe machine and also enumerate various operations which can be performed on it. 20 marks
Ans: Refer Page 94-97 of BME - Basant Agrawal, Wiley India
Unit-III
3. What is Newton's law of viscosity
A plate rquires 2 N force per unit area or 2 N/m² to move with a velocity of 60 cm/s over a fixed plate. The distance between two plates is 0.03 mm. Determine the fluid viscosity between the plates. 5+15 marks
Ans: Refer Page 115-116 of BME - Basant Agrawal, Wiley India (Ans: 0.1 centipoise)
Or
Derive the Bernoulli's equation from Euler's equation for an ideal flow.
The water is flowing through a pipe having diameters 20 cm at inlet section 1 and 10 cm at outlet section 2. The rate of flow through pipe is 35 litres/s. The section 1 is 6 m above datum and section 2 is 4 m above datum. If pressure at section 1 is 39.24 N/cm², find the intensity of pressure at section 2. 6+14 marks
Ans: Refer Page 125 & 129 of BME - Basant Agrawal, Wiley India (Ans: 40.27 N/cm²)
Unit-IV
4. Explain the First Law of Thermodynamics with suitable examples.
In a gas turbine the gas enters at the rate of 5 kg/s with a velcity of 50 m/s and enthalpy of 900 kJ/kg and leaves the turbine with a velocity of 150 m/s and enthalpy of 400 kJ/kg. The loss of heat from the gases to the surroundings is 25 kJ/kg. Assume for gas R = 0.285 kJ/kg-K and Cp = 1.004 kJ/kg-K and the inlet section conditions to be at 100 kPa and 27ºC. Determine the power output of the turbine and diameter of the inlet pipe. 6+14 marks
Ans: Refer Page 164-165 (article 9.1. and 9.2) of BME - Basant Agrawal, Wiley India (Ans: 2325 kW, 33 cm)
Or
Give the two statements of Second Law of Thermodynamics.
Which is the more effective way to increase the efficiency of a Carnot engine: To increase T1 keeping T2 constant or To decrease T2 keeping T1 constant. where T1 is the source temperature and T2 is the sink temperature. 20 marks
Ans: Refer Page 219-221 of BME - Basant Agrawal, Wiley India
To decrease T2 keeping T1 constant is the more effective way.
Unit -V
5. Show that the efficiency of the Otto cycle depends only on the compression ratio.
In a SI engine working on the ideal Otto cycle, the compression ratio is 5.5. The pressure and temperature at the beginning of compression are 1 bar and 27 ºC respectively. The peak pressure is 30 bar. Determine the pressure and temperatures at the salient points, the air-standard efficiency and the mean effective pressure. Assume ratio of specific heats to be 1.4 for air. 6+14 marks
Ans: Refer Page 306-307 of BME - Basant Agrawal, Wiley India (Ans: P2= 10.9 bar, T2=593.3 K, T3=1363.3K, efficiency=49.43%, Pm=5.25 bar)
Or
What is the basic difference between an Otto cycle and a Diesel cycle?
Derive the expression for the efficiency and mean effective pressure of the diesel cycle. 6+14 marks
Ans: Refer Page 321, 314-316 of BME - Basant Agrawal, Wiley India.
Solution 4
