This set of Farm Machinery Multiple Choice Questions & Answers (MCQs) focuses on “I.C Engine – Terminology Related to Engine Power”.

1. What is the formula for indicated mean effective pressure?

a) P_{i} = \(\frac{(Area \, of \, indicator \, diagram)}{Length \, of \, indicator \, diagram \, * \, spring \, scale \, index} \)

b) P_{i} = \(\frac{(Length\, of \, indicator \, diagram \, * \, spring\, scale \,index)}{Area\, of \,indicator \, diagram} \)

c) P_{i} = \(\frac{Length \, of \, indicator \, diagram}{Area \,of \,indicator\, diagram \, * \, spring \, scale \, index} \)

d) P_{i} = \(\frac{Spring \, scale \, index}{Area \, of \, indicator \, diagram \, * \, Length \, of \, indicator \, diagram} \)

View Answer

Explanation: Indicated mean effective pressure is the algebraic sum of the mean pressures acting on the piston during each stroke over one complete cycle. It is measured through indicator diagram drawn with the help of an engine indicator.

2. What is value of ‘n’, if there is no missing cycle, in brake power when it is applied as double acting, two stroke engines?

a) 2N

b) N

c) N/2

d) 4N

View Answer

Explanation: Brake power is the actual work output of an engine or the actual work available at the crankshaft or flywheel. It is also called shaft power and is given by:

B.P.= \(\frac{2πnT}{60000}\) KW.

3. What is the formula for specific fuel consumption (i.s.f.c.)?

a) i.s.f.c.=\(\frac{60 I.P.}{Wf} \)

b) i.s.f.c.=\(\frac{60 Wf}{I.P.} \)

c) i.s.f.c.=\(\frac{120 Wf}{I.P.} \)

d) i.s.f.c.=\(\frac{120 I.P.}{Wf} \)

View Answer

Explanation: The total consumption of fuel by an engine under test conditions in a given time is determined by measuring its volume or weight. The specific fuel consumption is defined as the total consumption per hour or per KW developed.

4. What is the name of the phenomenon caused in a governor in which the speed of the engines fluctuates continuously above and below the mean speed?

a) Firing interval

b) Air-Supply measurement

c) Sensitiveness of Governor

d) Governor hunting

View Answer

Explanation: A governor is said to be hunt if the speed of the engines fluctuates continuously above and below the mean speed. This is caused by a too sensitive governor which changes the fuel supply by a large amount when a small change in the speed of rotation takes place.

5. What is the formula of controlling force (F_{c}) of a governor?

a) F_{c} = n^{2} ω r

b) F_{c} = m ω r

c) F_{c} = m ω^{2} r

d) F_{c} = m ω r^{2}

View Answer

Explanation: In case of governor running at a steady speed, the inward force acting on the rotating balls is known as controlling force. It is equal and opposite to the centrifugal reaction. The formula of controlling force (F

_{c}) of a governor is F

_{c}= m ω

^{2}r.

6. A four cylinder two- stroke cycle engine with a swept volume of 750 cm^{3} per cylinder gives a specific fuel consumption of 0.25 kg KW^{-1} h^{-1}. When developing a brake mean effective mean pressure 650 kPa at 1500 rpm. What is the brake thermal efficiency, if the calorific value is 40 MJ kg^{-1}?

a) 9%

b) 18%

c) 32%

d) 36%

View Answer

Explanation:

Brake power = \(\frac{pLAN*n}{60000} \)

B.P. = \(\frac{650∗750∗10^{−6}∗1500∗ 4∗10^3}{60000} \)

B.P. = 48.75 KW

Brake thermal efficiency = \(\frac{B.P.*60}{Wf*Cf} \)

B.T.E. = \(\frac{48.75∗60}{0.203∗40∗10^3} \)

B.T.E. = 36%.

7. Which of the following is not a type of transmission dynamometer?

a) Epicyclic train dynamometer

b) Belt transmission dynamometer

c) Rope break dynamometer

d) Torsion dynamometer

View Answer

Explanation: In rope break dynamometer, the power is expressed by

P = \(\frac{[(W-S)π(D+d)N]}{60000} \)

Where, W is the dead load

S is the spring balanced

D is the diameter of the wheel

‘d’ is the diameter of the rope.

8. Engines of different cylinder dimensions, power and speed can be compared on the basis of __________

a) maximum pressure

b) fuel consumption

c) mean effective pressure

d) unit power

View Answer

Explanation: Basically, it is unit measurement of the output that the engine gives out. The development of the steam engine provided a reason to compare the output of horses with that of the engines that could replace them.

**Sanfoundry Global Education & Learning Series – Farm Machinery.**

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