# Farm Machinery Questions and Answers – Cooling System – 1

This set of Farm Machinery Multiple Choice Questions & Answers (MCQs) focuses on “Cooling System – 1”.

1. What is the range of best operating rating temperature of I.C. engine?
a) 106°F – 120°F
b) 140°F – 200°F
c) 106°F – 200°F
d) 120°F – 140°F

Explanation: For satisfactory performance of the engine, neither overheating nor over-cooling is desirable. Experiments have shown that best operating of I.C. engine lies between 140°F to 200°F depending upon types of engine and load conditions.

2. What are the different temperatures at which thermostats fully opens for petrol and diesel engine respectively?
a) 106°C;120°C
b) 89°C;98°C
c) 82°C;90°C
d) 100°C;102°C

Explanation: The purpose of thermostat is to close the water passage, between cylinder head and the top of radiator, when the engine is cold so that water circulation is restricted causing the engine to reach operating temperature more quickly. Thermostats are designed to start opening at 70°C-75°C and the fully open at 82°C for petrol and 90°C for diesel engine.

3. Which of the following is not a method of water cooling?
a) Open jacket or hopper method
b) Open flame method
c) Thermosiphon method
d) Forced circulation method

Explanation: Open flame method is a method of ignition in which two gas jets, one burning continuously on the outside of the engine and the other jet coming in contact with first jet and the combustion takes place, are used for ignition.

4. What is the formula for Newton’s law of cooling?
a) $$\frac{dθ}{dt}$$ = KA (θ-θ0)
b) $$\frac{dθ}{dt}$$ = KA (θ+θ0)
c) $$\frac{dθ}{dt}$$ = KA (θ*θ0)
d) $$\frac{dθ}{dt}$$ = KA (θ/θ0)

Explanation: Newton’s law of cooling states that, the rate of heat radiated or lost by a body is directly proportional to the excess temperature, provided that the excess temperature is less as compared to the surrounding temperature.

5. What amount of washing soda and kerosene oil should be added in water to make a solution to clean the cooling system?
a) 2 kg water and 0.5 kg kerosene oil
b) 2.5 kg water and 1.5 kg kerosene oil
c) 1 kg water and 0.5 kg kerosene oil
d) 1.5 kg water and 2.5 kg kerosene oil

Explanation: The cooling system should be cleaned at suitable intervals to remove Rust and Scale. One kg of washing soda and 0.5 kg of kerosene oil should be added to 10 kg of water to make a solution. The radiator should be filled with such solution and be allowed to remain there for 8 to 10 hours. After this, the engine should be started and run on medium speed. After 15 to 20 minutes the solution should be drained out.
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6. What is the maximum permissible V-belt sag?
a) 15 mm
b) 20 mm
c) 10 mm
d) 18 mm

Explanation: The tension of the fan belt should be checked very frequently. If the belt is very tight, it will cause wear on the pulley of pump and dynamo. The maximum permissible V-belt sag when applying average finger pressure is 15mm. If it is more than this limit, the belt should be adjusted.

7. A capillary tube has a diameter of 3 mm and 100 mm length. A head of 10 cm of oil above the inlet of the capillary maintains a pressure difference across the capillary. The specific gravity of oil is 0.92. A volume of 300 cm3 of oil passes through the in 10s. What will be the viscosity of oil?
a) 5.68 * 10-4 poise
b) 5.98 * 10-4 poise
c) 5.68 * 10-5 poise
d) 5.98 * 10-5 poise

Explanation: p = ρgh
P = 0.92 * 981 * 1
P = 902.52 dyne/cm2
Now,
η = $$\frac{π p r^4 t}{8Vl} = \frac{[π*902.52*(0.15)^4*10]}{8*300*10}$$ = 5.98 * 10-4poise.

8. What is the temperature dropping in the radiator of a tractor when the flow rate of water is 0.16 litre per second per KW?
a) 8.5°C to 5.5 °C
b) 11°C to 10 °C
c) 20°C to 15 °C
d) 12.75 °C to 9.79°C

Explanation: In tractors, the required flow rate of water is 0.16 litre per sec per KW to drop radiator temperature 8.5°C to 5.5°C. At 2000 rpm the diesel engine and petrol engine rejects 0.58 and 0.75 KW for each kilo watt output respectively.

Sanfoundry Global Education & Learning Series – Farm Machinery.