**1. Carnot Cycle consists of**

(a) Two constant pressure and two isentropic processes

(b) One constant isenthalpic, one constant volume and two constant pressure processes

(c) Two isothermal and two isentropic processes

(d) One constant pressure, one constant volume and two isothermal processes

**2. One reversible heat engine operates between 1600°K and T**_{2}°K and another reversible heat engine operates between T_{2}°K and 400°K. If both the engines have the same heat input and output, then temperature T_{2} is equal to

(a) 800 K

(b) 1600 K

(c) 1200 K

(d) 6400 K

Answer

Option (a) is correct

**Since both engine have same heat input and output, so we can say**

\(\eta_{E1}=\eta_{E2}\)

\(\large 1-\frac{T_2}{1600}=1-\frac{400}{T_2}\)

\(T_2^2=1600\times400\)

\(T_2=800K\)

**3. Isentropic flow is**

(a) Reversible adiabatic flow

(b) Irreversible adiabatic flow

(c) Frictionless fluid flow

(d) Reversible isothermal flow

**4. Reversed Joule cycle is known as **

(a) Rankine cycle

(b) Carnot cycle

(c) Bell-Coleman cycle

(d) Otto cycle

Answer

Option (c) is correct

**Reversed Joule cycle is known as Bell-Coleman cycle.**

**5. The thermal efficiency of Gas turbine plant is **

(a) \(r^{\gamma -1}\)

(b) \(1-r^{\gamma -1}\)

(c) \(1-\left ( \frac{1}{r} \right )^{\frac{\gamma }{\left ( \gamma -1 \right )}}\)

(d) \(1-\left ( \frac{1}{r} \right )^{\frac{\left ( \gamma -1 \right )}{\gamma }}\)

**Where r is pressure ratio and γ is relation between specific heats.**

Answer

Option (d) is correct

**It is just asking the efficiency formula for Brayton cycle.**

**6. A 100 W electric bulb was switched on in a 2.5 m × 3m × 3 m size thermally insulated room having temperature of 20°C. The room temperature at the end of 24 hrs. will be **

(a) 100°C

(b) 470°C

(c) 370°C

(d) 600°C Consider density and specific heat of air as 1.2 kg/m^{3} and 0.718 kW/°C/kg

**7. A solar energy based heat engine which receives 80 kJ of heat at 100°C and rejects 70 kJ of heat to the ambient at 30°C is to be designed. The thermal efficiency of heat engine is**

(a) 70%

(b) 18.8%

(c) 12.5%

(d) cannot be calculated

Answer

Option (c) is correct

**The thermal efficiency of heat engine is given as**

\(\large \eta=1-\frac{Q_2}{Q_1}=1-\frac{70}{80}\)

\(\eta=0.125=12.5\%\)

**8. A mixure of gases expand from 0.03 m**^{3} to 0.06 m^{3} at constant pressure of 1 MPA and absorb 84 kJ of heat during the process. The change in internal energy of the mixture is

(a) 54 kJ

(b) 30 kJ

(c) 84 kJ

(d) 110 kJ

Answer

Option (a) is correct

**We know that**

\(Q=dU+W\)

where,

\(Q=+84\;kJ;\;\;W=10^3(0.06-0.03)=30\’kJ\)

**So we get,**

\(84+dU+30;\;\;dU=54\;kJ\)

**9. If the concentrated load applied at the free end of a cantilever beam is doubled along with its length and moment of inertia also, then the deflection at free end will increase by **

(a) 2 times

(b) 4 times

(c) 8 times

(d) 12 times

Answer

Option (c) is correct

**We know that deflection at free end is given as**

\(\large \delta=\frac{Pl^3}{3EI}\)

**Now if, **

\(P’=2P,\;\;L’=2L,\;\;I’=2I\)

**we get,**

\(\large \delta’=\frac{2P\times (2l)^3}{3E(2I)}=8\delta\)

**10. In the case of a beam simply supported at both ends, if the same load instead of being concentrated at centre is distributed uniformly throughout the length, then deflection at centre will get reduced by**

(a) 1/2 times

(b) 1/4 times

(c) 5/8 times

(d) 3/8 times

Answer

Option (d) is correct

**For point loading on cantilever, we have**

\(\large \delta_p=\frac{Pl^3}{48EI}\)

**Deflection for UDL, we have **

\(\large \delta_{udl}=\frac{5}{384}\frac{ql^4}{EI}=\frac{5}{384}\frac{Pl^3}{EI}\)

where \(q=Pl\)

**Taking the ratio of two, we have**

\(\large \frac{\delta_{udl}}{\delta_{p}}=\frac{5}{384}\times48=\frac{5}{8}\)

**So the reduction is given by**

\(\large \delta_p-\delta_{udl}=\delta_p-\frac{5}{8}\delta_p=\frac{3}{8}\delta_p\)

**Note: Its simple question with a tricky language.**

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