Thermal Properties of Matter Physics - Thermal Properties of Matter

‘Gulab Jamuns’ (assumed to be spherical) are to be heated in an oven. They are available in two sizes, one twice bigger (in radius) than the other. Pizzas (assumed to be discs) are also to be heated in oven. They are also in two sizes, one twice big (in radius) than the other. All four are put together to be heated to oven temperature. Choose the correct option from the following:

1. Both size gulab jamuns will get heated in the same time.
2. Smaller gulab jamuns are heated before bigger ones.
3. Smaller pizzas are heated before bigger ones.
4. Bigger pizzas are heated before smaller ones.

Mark the correct options:

1. A system X is in thermal equilibrium with Y but not with Z. System Y and Z may be in thermal equilibrium with each other.
2. A system X is in thermal equilibrium with Y but not with Z. Systems Y and Z are not in thermal equilibrium with each other.
3. A system X is neither in thermal equilibrium with Y nor with Z. The systems Y and Z must be in thermal equilibrium with each other.
4. A system X is neither in thermal equilibrium with Y nor with Z. The system Y and Z may be in thermal equilibrium with each other.

Refer to the plot of temperature versus time showing the changes in the state of ice on heating (not to scale). Which of the following is correct?

1. The region AB represents ice and water in thermal equilibrium.
2. At B water starts boiling.
3. At C all the water gets converted into steam.
4. C to D represents water and steam in equilibrium at boiling point.

As the temperature is increased, the time period of a pendulum:

1. Increases as its effective length increases even though its centre of mass still remains at the centre of the bob.
2. Decreases as its effective length increases even though its centre of mass still remains at the centre of the bob.
3. Increases as its effective length increases due to shifting of centre of mass below the centre of the bob.
4. Decreases as its effective length remains same but the centre of mass shifts above the centre of the bob.

A uniform metallic rod rotates about its perpendicular bisector with constant angular speed. If it is heated uniformly to raise its temperature slightly:

1. Its speed of rotation increases.
2. Its speed of rotation decreases.
3. Its speed of rotation remains same.
4. Its speed increases because its moment of inertia increases.

Is the bulb of a thermometer made of diathermic or adiabatic wall?

These days people use steel utensils with copper bottom. This is supposed to be good for uniform heating of food. Explain this effect using the fact that copper is the better conductor.

Calculate the temperature which has same numeral value on celsius and Fahrenheit scale.

Why does a metal bar appear hotter than a wooden bar at the same temperature? Equivalently it also appears cooler than wooden bar if they are both colder than room temperature.

100 g of water is supercooled to -10°C. At this point, due to some disturbance mechanised or otherwise some of it suddenly freezes to ice. What will be the temperature of the resultant mixture and how much mass would freeze?
[Sw = 1cal/ g/°C and L^W_Fusion = 80cal/ g]

During summers in India, one of the common practice to keep cool is to make ice balls of crushed ice, dip it in flavoured sugar syrup and sip it. For this a stick is inserted into crushed ice and is squeezed in the palm to make it into the ball. Equivalently in winter, in those areas where it snows, people make snow balls and throw around. Explain the formation of ball out of crushed ice or snow in the light of P–T diagram of water.

One day in the morning, Ramesh filled up 1/ 3 bucket of hot water from geyser, to take bath. Remaining 2/ 3 was to be filled by cold water (at room temperature) to bring mixture to a comfortable temperature. Suddenly Ramesh had to attend to something which would take some times, say 5-10 minutes before he could take bath. Now he had two options:

1. Fill the remaining bucket completely by cold water and then attend to the work.
2. First attend to the work and fill the remaining bucket just before taking bath. Which option do you think would have kept water warmer? Explain.