# Farm Machinery Questions and Answers – Cooling System – 2

This set of Farm Machinery Questions and Answers for Campus interviews focuses on “Cooling System – 2”.

1. Which law states that the rate of heat radiated by a body is directly proportional to the excess of temperature, provided that the excess temperature is less as compared to the surrounding temperature?
a) Pascal’s law
b) Newton’s law of cooling
c) Einstein’s equation
d) Henry’s law

Explanation: Newton’s law of cooling states that the rate of heat radiated by a body is directly proportional to the excess of temperature, provided that the excess temperature is less as compared to the surrounding temperature. It is expressed as
$$\frac{∂θ}{∂t}$$ = KA(θ-θ0)

2. What output do the engines reject running at a speed of 2000 rpm and at full load condition using gasoline?
a) 0.75 KW
b) 0.89 KW
c) 0.23 KW
d) 0.44 KW

Explanation: The engines, at the speed of 2000 rpm and at full load condition, using gasoline with 7.3:1 compression ratio reject approximately 0.75 KW for each kilowatt of output.

3. What would be the quantity of water to be circulated through the radiator, if diesel tractor developed 40 KW with a coolant temperature difference of 5.5°C?
a) 4.26 lps
b) 4.19 lps
c) 2.86 lps
d) 3.72 lps

Explanation:
In tractors, the required flow rate of water is 0.16 l/s per kw to drop the radiator temperature from 5.5 to 8.5°C
Q = 40*0.58*0.16 l/s = 3.72 lps

4. A body cools from 70°C to 40°C in 5 minutes at surrounding temperature of 10°C. How long will it take for the body to cool from 49°C to 25°C?
a) 4.3 minutes
b) 6.5 minutes
c) 3.3 minutes
d) 1.8 minutes

Explanation:
According to Newton’s Law of cooling
$$\frac{Q1-Qs}{Q2-Qs}$$αt
$$\frac{49-10}{25-10}=\frac{5}{t}$$
T = 6.5 minutes

5. A diesel tractor develops 60 KW with a coolant temperature difference 5.5°C. What will be the quantity of water to be circulated through the radiator?
a) 3.72 l/s
b) 5.56 l/s
c) 9.88 l/s
d) 11.10 l/s

Explanation:
In tractors, the required flow rate of water is 0.16 l/s per kw to drop the radiator temperature from 5.5 to 8.5°C
Q = 60*0.58*0.16 l/s = 5.56 lps
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6. What is the temperature of burning gases in the engine?
a) 3000-4000°C
b) 1500-2000°C
c) 11000-12000°C
d) 9000-10000°C

Explanation: The temperature of burning gases in the engine cylinder reaches up to 1500-2000°C which is above the melting point of the material of the cylinder body and head of engine.

7. What is the melting point of Platinum?
a) 1750°C
b) 2050°C
c) 850°C
d) 750°C

Explanation: Platinum, a metal which has one of the highest melting point, melts at 1750°C

8. What is the temperature of water in a closed radiator under high pressure?
a) 319°F
b) 123°F
c) 264°F
d) 243°F

Explanation: In the case of the ordinary water cooling system where the cooling water is subjected to atmospheric pressure, the water boils at 212°F. But when water is boiled in a close radiator under high pressure, the boiling temperature of water increases to 243°C.

9. At what temperature does the thermostats fully open?
a) 36°C
b) 98°C
c) 82°C
d) 42°C

Explanation: Thermostat valve is a kind of check valve which opens and closes with the effect of temperature. Standard thermostats are designed to start opening at 70°C and they fully open at 82°C.

10. Who invented the automobile water radiator?
a) Wilhelm Maybach
b) Karl Benz
c) Elon Musk
d) Alfred Noble

Explanation: The invention of the automobile water radiator is attributed to Karl Benz. The first honeycomb radiator is designed by Wilhelm Maybach for the Mercedes 35hp. Mercedes 35hp is the first successful cooling system vehicle.

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