The cast iron when heated to red heat with powdered red haematite in an oven for increasing its toughness, is converted to

Land masses are heated and cooled much faster than water bodies. Identify the true statements in this regard:
I. Land gets heated by conduction
II. Water has higher specific heat
III. Only the surface layers of water are heated
IV. Water gets heated by convection

A

I, II and III

B

II and III

C

I and IV

D

I, II and IV

Which variety of cast iron is obtained by melting cast iron with wrought iron scrap?

A

Mottled cast iron

B

Chilled cast iron

C

Malleable cast iron

D

Toughened cast iron

Below is the list of colors nominated as the favorite colors by students of class I. Determine the color which has frequency 9. red, blue, red, yellow, green, yellow, green, yellow, yellow, red, green, red, blue, red, yellow, red, blue, yellow, red, blue, blue, yellow, yellow, green, green

A

red

B

blue

C

green

D

yellow

Out of the total production of iron from hematite, an ore of Iron, 20% of the ore gets wasted, and out of the remaining iron, only 25% is pure iron. If the pure iron obtained in a year from a mine of hematite was 80,000 kg, then the quantity of hematite mined from that mine in the year is

A

5,00,000 kg

B

4,00,000 kg

C

4,50,000 kg

D

None of these

Which of the following statements are true with respect to iron ore?
I. Limestone and coal are important for smelting iron ore
II. More than 20% of the world iron ore deposits are in India
III. Odisha and Jharkhand top in the production of iron ore
IV. Iran is the largest buyer of Indian iron ore

A

I, II and III

B

II and III

C

III and IV

D

II, III and IV

Consider the figures of a metal ball and a metal ring given below.
The metal ball can just pass through the hole of a metal ring formed out of a strip. When the ball is heated it gets stuck. But when the metal is heated
Heat and Thermodynamics mcq question image

Heat and Thermodynamics mcq question image

A

The ball can still pass through the ring as diameter expands on heating

B

The ball gets stuck because of the diameter of the hole decrease on expansion

C

The ball will still pass through because the hole diameter does not change

D

The ball will pass through because there is no change in the ring

A cold fluid (specific heat 2.95 k J/kg K) at 10 kg/min is to be heated from 25 degree Celsius to 55 degree Celsius in a heat exchanger. The task is accomplished by extracting heat from hot water (specific heat 4.186 k J /kg K) available at mass flow rate 5 kg/min and inlet temperature 85 degree Celsius. Identify the type of arrangement of the heat exchanger

A

Concentric tubes

B

Parallel flow

C

Counter flow

D

Shell and tubes

In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the effectiveness of the heat exchanger. At the condensing pressure, stream has a saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to the water. Take specific heat of water as 4 k J/kg K

A

0.224

B

0.706

C

2.224

D

3.224

In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m2 hr degree. Find the number of transfer units of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K

A

3.224

B

2.224

C

1.224

D

0.224

A Carnot heat engine receives heat at 750 K and rejects the waste heat to the environment at 300 K. The net work output of the heat engine is used to drive a Carnot refrigerator, whose COP is 6.14. If the heat removal rate from the refrigerated space is 6.6 kW, determine the rate of heat supply to the heat engine?

A

2.79 kW

B

1.79 kW

C

4.79 kW

D

7.79 kW

The cast iron when heated to red heat with powdered red haematite in an oven for increasing its toughness, is converted to

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