Description : In a house, there lives a family of 4. There is a father, a mother, an older sister, and a younger sister. One day, the father catches a disease. A week later, Death comes to take the ... will live until this candle burns out.' And Death agrees. However, Death never returns. Why not? -Riddles
Last Answer : The younger sister blew out the candle, so it didn't technically burn out. Then she threw away the candle so the family wouldn't mistakenly light it.
Description : A candle flame 2 cm high is palced at distance of 2 metere from a wall. How far from the wall must a concave mirror to placed in order to form an imag
Last Answer : A candle flame 2 cm high is palced at distance of 2 metere from a wall. How far from the wall must ... an images of the flame 6 cm high on the wall ?
Description : Which zone of a candle flame is the hottest? (1) Dark innermost zone (2) Outermost zone (3) Middle luminous zone (4) Central zone
Last Answer : (3) Middle luminous zone Explanation: The outermost zone of the flame is blue in colour and it is the hottest part. The innermost zone is the least hot and black in colour.
Description : What happens when a piece of bangle is heated in a candle flame?
Last Answer : When a piece of bangle is heated in a candle flame, it first becomes soft and then melts as glass does not have a definite melting point.
Description : Cannel coal (A) Is non-coking (B) Has a high volatile matter content and burns with a luminous smoky flame (C) Is a non-banded coal which can be ignited easily with a match stick or candle flame, hence is so named (D) All (A), (B) and (C
Last Answer : (D) All (A), (B) and (C
Description : A student focuses the image of a candle flame, placed at about 2 m from a convex lens of focal length 10 cm, on a screen. After that he moves gradually the flame towards the lens and each time focuses its ... d) What is seen on the screen when the flame is very close (at about 5 cm) to the lens?
Last Answer : (a) The student moves the lens away from the screen to focus the image because on moving the candle towards the lens, the image distance increases. (b)The size of the image increases when the object ... on the screen. A virtual image is formed behind the candle on the same side of the screen.
Description : On placing an inverted tumbler over a burning candle, the flame extinguishes after some – time . This is because of non –availability of a) oxygen b)water vapour c)carbon dioxide d)wax
Last Answer : a) oxygen
Description : The ________ zone of a candle flame is the hottest zone. a) innermost b)outermost c)middle d)none
Last Answer : b)outermost
Description : The middle zone of a candle flame is known as the ________ zone. a) luminous b)non-luminous c)wax d)burning
Last Answer : a) luminous
Description : Which of the following has the highest theoretical flame temperature? (A) Blast furnace gas (B) Hydrogen (C) Acetylene (D) Coke oven gas
Last Answer : (C) Acetylene
Description : Which of the following has the highest flame speed? (A) CO (B) H2 (C) CH4 (D) C2H6
Last Answer : (B) H2
Description : Which of the following has the highest flame velocity? (A) H2 (B) CO (C) CH4 (D) C2H6
Last Answer : (A) H2
Description : The temperature of oxyacetylene flame is around – (1) 2800°C (2) 3200°C (3) 4000°C (4) 1500°C
Last Answer : (2) 3200°C Explanation: Flames are formed when a fuel gas, like acetylene, reacts with a support has such as oxygen. This reaction creates a lot of heat and light, which we see as a flame. ... flame temperature to allow localized melting of the work piece material (e.g. steel) in a room environment.
Description : Radian is used to measure - (1) Temperature (2) Intensity of Flame (3) Angle (4) Solid Angle
Last Answer : (3) Angle Explanation: Kelvin is used to measure Temperature, Candela is used to measure Intensity of flame, Steredian is used to measure Solid Angle.
Description : In case of liquid petrofuels, momentary combustion is observed at its (A) Flash point (B) Preheating temperature corresponding to viscosity of 25 centistokes (C) Flame temperature (D) Fire point
Last Answer : (A) Flash point
Description : Smoke point of kerosene is the (A) Time after which smoking starts on burning (B) Temperature at which smoking starts (C) Maximum height of flame (in mm) without causing smoking, when burnt in a standard lamp (D) None of these
Last Answer : (B) Temperature at which smoking starts
Description : Oxygen enrichment of combustion air does not result in increase of the (A) Flame temperature (B) Oxygen in the flue gas (C) Stack loss (D) Heat transfer rate in the furnace
Last Answer : (B) Oxygen in the flue gas
Description : Advantages of use of preheated combustion air are (A) Saving in fuel consumption (B) Reduction in scale losses (C) Increase in flame temperature (D) All (A), (B) and (C)
Last Answer : (D) All (A), (B) and (C)
Description : Air filtration in a furnace (A) Reduces its thermal efficiency (B) Is indicated by flame sting out (C) Increases the flue gas temperature (D) None of these
Last Answer : (A) Reduces its thermal efficiency
Description : Combustion of fuel in a furnace with oxygen enriched air results in higher (A) Flue gas volume (B) Flame temperature (C) Fuel consumption (D) Stack loss
Last Answer : (B) Flame temperature
Description : Which of the following advantages is not associated with the use of preheated air for combustion of a fuel in the furnace? (A) Increase in calorific value of the fuel (B) Increase in flame temperature (C) Reduction in scale losses (D) Saving in fuel consumption
Last Answer : (A) Increase in calorific value of the fuel
Description : Pick out the wrong statement. (A) Theoretical flame temperature is the temperature attained by the products of combustion, when the fuel is burned without loss or gain of heat (B) ... flame temperature (D) Adiabatic flame temperatures of actual combustions are always less than the maximum values
Last Answer : (C) Burning the fuel with excess pure oxygen results in maximum theoretical flame temperature
Description : During combustion of gaseous fuels, deficiency of air (A) Lengthens the flame (B) Tends to shorten the flame (C) Does not affect the flame length (D) Increases the flame temperature
Last Answer : (A) Lengthens the flame
Description : The ratio of maximum adiabatic flame temperature in air to that in pure oxygen is always (A) 1 (B) < 1 (C) > 1 (D) Unpredictable
Last Answer : (B) < 1
Description : Preheating of combustion air is done to (A) Increase the adiabatic flame temperature (B) Increase the calorific value of the fuel (C) Complete the combustion of fuel (D) Reduce its requirement for effecting the complete combustion
Last Answer : (A) Increase the adiabatic flame temperature
Description : Actual flame temperature is always lower than the adiabatic flame temperature, because there is (A) No possibility of obtaining complete combustion at high temperature (B) Always loss of heat from the flame (C) Both (A) and (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) and (B)
Description : Combustion of pulverised coal as compared to that of lump coal (A) Develops a non-luminous flame (B) Develops a low temperature flame (C) Can be done with less excess air (D) Provides a lower rate of heat release
Last Answer : (C) Can be done with less excess ai
Description : The maximum adiabatic flame temperature in air as compared to that in pure oxygen is (A) Much lower (B) Much higher (C) Same (D) Either lower or higher, depends on the type of fuel
Last Answer : (A) Much lower
Description : Preheating of a gaseous fuel results in increased (A) Flame length (B) Flame temperature (C) Quantity of flue gas
Description : A coal containing high amount of volatile matter will have (A) Low ignition temperature (B) Very little ash content (C) High fusion point of its ash (D) Low adiabatic flame temperature
Last Answer : (A) Low ignition temperature
Description : Coke oven gas is a better fuel than blast furnace gas, because of its higher (A) Calorific value, cleanliness and relatively low distribution cost (due to its low specific gravity) (B) Adiabatic flame temperature ... release rate (thus requiring smaller combustion chamber) (D) All (A), (B) and (C)
Description : Presence of nitrogen in combustion air does not reduce the (A) Amount of heat liberated (B) Flame temperature (C) Flue gas temperature (D) Any of the above
Last Answer : (A) Amount of heat liberated
Description : Preheating of __________ the flame temperature. (A) The gaseous fuel before combustion decreases (B) Combustion air decreases (C) Either the fuel or the air or both, increases (D) Either the fuel or the air does not affect
Last Answer : (C) Either the fuel or the air or both, increases
Description : For the case of a fuel gas undergoing combustion with air, if the air/fuel ratio is increased, the adiabatic flame temperature will (A) Increase (B) Decrease (C) Increase or decrease depending on the fuel type (D) Not change
Last Answer : (B) Decrease
Description : The maximum adiabatic flame temperature is attained, when the fuel is burnt with (A) Theoretically required amount of air (B) More than theoretically required amount of air (C) Less than theoretically required amount of air (D) Theoretically required amount of oxygen
Last Answer : (D) Theoretically required amount of oxygen
Description : Theoretical flame temperature of a fuel is that temperature which is attained, when the fuel is completely burnt 'using theoretical amount of air in (A) Air (B) Oxygen (C) Either (A) or (B) (D) Either (A) or (B) without gain or loss of heat
Last Answer : (D) Either (A) or (B) without gain or loss of heat
Description : A fuel with high heat release rate will (A) Require smaller combustion chamber (B) Have high calorific value (C) Have high adiabatic flame temperature (D) None of these
Last Answer : (A) Require smaller combustion chamber
Description : Use of preheated air for combustion of fuel in the furnace, increases the (A) Scale losses of the furnace stock (B) Calorific value of the fuel (C) Flame temperature (D) None of these
Last Answer : (C) Flame temperature
Description : Blast furnace gas compared to coke oven gas has (A) Lower ignition temperature (B) Narrower limit of inflammability (C) Higher calorific value (D) Lower theoretical flame temperature
Last Answer : (D) Lower theoretical flame temperature
Description : Combustion of pulverised coal compared to the lumpy coal (A) Provides better control of furnace temperature (B) Facilitates combustion with lower excess air (C) Provides higher thermal efficiency & flame temperature (D) All (A), (B) & (C)
Last Answer : (D) All (A), (B) & (C)
Description : Adiabatic flame temperature of a fuel is dependent on the initial temperature of (A) Fuel (B) Air (C) Both (A) & (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) & (B)
Description : If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will be (A) Low (B) High (C) Very high, if the fuel is of low calorific value (D) None of these
Last Answer : (A) Low(A) Low
Description : The maximum adiabatic flame temperature in air is __________ the maximum flame temperature in pure oxygen. (A) Lower than (B) Higher than (C) Same as (D) Not related to
Last Answer : (A) Lower than
Description : Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature? (A) Calorific value of the fuel (B) Flame temperature achieved (C) Speed of combustion of fuel (D) Heat transfer rate to the stock in the furnace
Last Answer : (A) Calorific value of the fuel
Description : While the oxy-acetylene flame produces a temperature of 3200°C, the temperature produced by oxy-hydrogen flame is about __________ °C. (A) 1800 (B) 2000 (C) 2400 (D) 3000
Last Answer : (B) 2000
Description : In the blast furnace, incorporation of water vapour in the blast gives the following effect. (A) Increases the reducing potential of the gas (B) Increases the flame temperature (C) No significant change occurs (D) Increases the hydrogen content in the metal
Last Answer : (A) Increases the reducing potential of the gas
Description : Infrared thermometer is used to measure a) Surface temperature b) Flame temperature c) Flue gas temperature d) Hot water temperature
Last Answer : Surface temperature
Description : The temperature at which flame persists for approximately five seconds is called..... (a) Fire point (b) Flash point (c) Pour point (d) cloud point
Last Answer : (a) Fire point
Description : Explain the effect of the following engine variables on ignition lag and flame propagation: (i) cylinder size (ii) cylinder wall temperature (iii) compression ratio and (iv) inlet air temperature
Last Answer : (i) Cylinder size - Engine of similar design generally run at the same speed. This is achieved by smaller engine having larger RPM and larger engines having smaller RPM. Due to the same ... all reduces the ignition lag. Pre-increase in the intake temperature and pressure increases the flame speed.