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1. The bulbs is not light up, because, the coin and the spoke do not touch it. The circuit is not completed. 

2. Yes, the bulb is light up, because the spoke is heated the circuit is completed. 

3. When the spoke is heated, it will be expanded. Here, linear expansion takes place. So it touched the coin. 

4. After removing the candle, the spoke does not get the heat. The spoke is returned to its original state. So it does not touch the coin once again and the bulb goes off. 

5. The length of the spoke is expanded when the spoke is heated.

Correct Answer is: (c) independent of l

Let α = coefficient of thermal expansion, Y = Young modulus of the wire. If the wire were free to contract, its decrease in length would be lαt, where t = decrease in temperature. To maintain constant length, lαt becomes the effective elongation. 

∴ strain = lαt/l = αt.

Let T = tension ∴ stress = T/A

Using Y = stress/strain,T = YAαt.

Correct Answer sis: (a) Y₁α₁ = Y₂α₂ 

Tension must be the same in both the rods for their junction to be in equilibrium. 

Y₁Aα₁t = Y₂Aα₂t. 

m = 200 g (1 ml of water = 1 gm of water) 

S = 1 cal/gm °C ; 

t₁ = 20° C; t₂ = 37° C 

Q = mS∆T (∆T = t₂ – t₁ ) 

= 200 × 1 × (37 – 20) 

= 200 × 17 

Q = 3400 calories

C) Principle of method of mixtures

No. climate is different from weather. The changes occur during the period of some hours is called changing in weather. Climate is average weather conditions of a long period. So he had to use weather instead of climate in his statement.

D) evaporation & condensation

Correct option is  B) fog

Procedure :

Place a glass tumbler on the table. Pour cold water up to half of its height. 

Observation : 

There are droplets formed outside of the glass. 

Explanation : 

• The reason is that the surrounding air contains water molecules in the form of water vapour. When the water molecules strike the surface of the glass tumbler which is cool, they lose their kinetic energy. 
• This energy lowers the temperature of vapour and it turns into droplets. 
• The energy lost by water molecules in air is gained by the molecules of the glass tumbler. 
• Hence the average kinetic energy of glass molecules increases. In turn the energy is transferred to water molecules in die glass. 

Conclusion : 

• So the average kinetic energy and temperature of water in glass increases. 
• This is called condensation. Condensation is the phase change from gas to liquid.

High temperatures, along with humidity sometimes may cause heat stroke or sunstroke.

Mercury Barometer and aneroid barometers are used to measure air pressure.

Thermometer is used to measure temperature.

The phase change from gas to liquid at the surface of the liquid is called condensation.

Hygrometer is used to measure humidity in air.

The amount of water vapor present in the air is called humidity.

Correct Answer is: (d) 1500 J/°C

Rate of loss of heat ∝ difference in temperature with the surroundings.

At 50°C, dQ/dt = k(50 - 20) = 10, where k = constant

 k = 1/3

At an average temperature of 35°C, dQ/dt = 1/3 (35 - 20) J/s = 5 J/s.

 Heat lost in 1 minute = dQ/dt x 60 J = 5 x 60 J = 300 J = Q.

Fall in temperature = 0.2°C Δθ.

Q = cΔθ.

Heat capacity = c Q/Δθ = 300 J/0.2°C.

Correct Answer is: (d) 2α Δt 

I = ∑mr²

I + ΔI = ∑m[r(1 + α Δt)]²

or I + ΔI = ∑[mr² (1 + 2α Δt)] = I(1 + 2 Δt)

or ΔI/I = 2α Δt.

Before use, the clinical thermometer is jerked so that the mercury flows back into the bulb.

The jerk to the thermometer will allow the mercury in or above the kink to flow into the bulb so that the mercury level is below normal temperature.

Correct Answer is: (c) γR/M(γ - 1)

Specific heat capacity = molar heat capacity/molecular weight.

Correct Answer is: (a, b, c, & d)

 The molar heat capacity has the general definition

C = 1/n . ΔQ/ΔT ,

where n = number of moles, ΔQ = heat absorbed by the gas and ΔT = rise in temperature of gas.

It is possible to obtain almost any set of values for ΔQ and ΔT by proper selection of a process.

Correct Answer is:(a, b, & d)

Correct Answer is: (a,b)

1. The latent heat of fusion of ice is sufficiently high. 

2. So to freeze water, a large quantity of heat has to be withdrawn, hence it freezes slowly and thus keeps the surroundings moderate.

1. When crushed ice is pressed, its melting point is lowered and some ice melts to form water.

2. When pressure is released, the melting point becomes normal and the water freezes to form ice forming a lump.

1. The temperature of the outer surface of a cold drink bottle is less than that of the atmosphere.

2. Therefore, the excess of water vapour from the air condenses to form droplets on the outer surface of the cold drink bottle.

1. In cold countries, in winter, a layer of ice is formed on the surface of lakes when the atmospheric temperature falls below 0 °C. However, below this layer, there is water at 4 °C.

2. Ice, being a bad conductor of heat, does not allow transfer of heat from this water to the atmosphere.

Hence, aquatic animals and plants can survive in this water.

A clean environment is essential for heathy living. So, we want a concrete plan to protect environment.

People use thermometers in homes, hospitals, automobiles, industries and restaurants etc., to measure temperatures of different objects and substances.

Clinical thermometer is used in hospitals to measure the temperature of the human body.

Thermometer works on the expansion of liquids (mercury).