The diagram shows a way of demonstrating a convection current in air. Explain why colder air flows downwards through the other 'chimney'.

When the air is heated its volume increases and hence become less dense, so it rises above which is replaced with cold air, so it flows downwards. Air-conditioners are used constantly. The process of cooling air in air-conditioners employs the very principle of convection. The air which is cold is released by the air-conditioners. Now, this cold air is denser than the warm air, and, hence, it sinks. The warm air, being less dense, rises and is drawn in by the air-conditioner. As a result, a convection current is set up and the room is cooled. The weight of the column of air is less than the weight of the column of smoke, so the pressure at the base of the column of smoke is lower than the pressure at the base of the column of air.

Liquid nitrogen, at a temperature of - 196 ° c , is stored in a wide-necked vacuum flask, as shown. Explain the features of the design of this flask that help to keep the liquid nitrogen cold.

Silvering on inside of glass prevents heat loss through reflection. Double walled glass flask and vacuum prevent heat loss through conduction. Vacuum prevent heat loss through radiation. Liquid nitrogen temperature ( − 196 ° C ) , and then the glass tube is evacuated. The stopcock is closed, and the N 2 baths is then removed. When melted, it is made to solidify at − 196 ° C , and the tube is evacuated again. The freezing and melting process is repeated until it is free of noncancelable impurity ( air ) .

Some water in a glass beaker is heated from below, as shown in the diagram. Name the process by which thermal energy is transferred : Through the glass.

Convection Heat can be transferred in liquids or gases by convection. Fluids Liquids and gases are fluids because they can be made to flow. The particles in these fluids can move from place to place. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Convection in a liquid Convection in a liquid can be seen by putting a crystal of potassium permanganate in a beaker of water and gently heating it with a Bunsen flame. Heat is initially transferred through the glass wall of the beaker by conduction. The water in the region of the Bunsen flame is heated. It expands, becomes less dense and rises. It is replaced by the cooler, denser water which surrounds it. This water is in turn heated, expands becomes less dense and rises. The process continues, a convection current is set up and heat is transferred through the liquid. Convection currents can be seen in lava lamps. The wax inside the lamp warms up, becomes less dense than the liquid and so rises.

Some water in a glass beaker is heated from below, as shown in the diagram. Name the process by which thermal energy is transferred : Throughout the water.

Thermal energy is transferred through water by a process known as 'CONVECTION'. In this process initially the water molecules present below a container absorb the heat, then they move upward and the molecules present above they move downward and the process continues. Water molecules undergo changes of state When these changes occur, thermal energy is either released or absorbed Released from liquid > solid Absorbed from Liquid > gas Temp. remains the same between phase changes. Through changes of state is how thermal energy is transferred through the biosphere

EASY

Upper Secondary: IGCSE

IMPORTANT

Earn 100

The diagram shows a way of demonstrating a convection current in air.

Explain why air rises above the hot flame.

Important Questions on Thermal (Heat) Energy Transfers

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 7

The diagram shows a way of demonstrating a convection current in air.

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Explain why colder air flows downwards through the other 'chimney'.

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 8

One end of a plastic rod is immersed in boiling water. The temperature of the other end gradually increases. Use ideas from the kinetic model of matter to explain how energy travels from one end of the rod to the other.

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 8

If the experiment was repeated using a metal rod of the same dimensions as the plastic rod, what difference would you expect to notice

?

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 8

What particles in a metal are involved in transferring energy from hotter to colder ones

?

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 9

Liquid nitrogen, at a temperature of $- 196 ° c$ , is stored in a wide-necked vacuum flask, as shown.

Question Image

Explain the features of the design of this flask that help to keep the liquid nitrogen cold.

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 9

Liquid nitrogen, at a temperature of $- 196 ° C$ , is stored in a wide-necked vacuum flask, as shown.

Question Image

When hot drinks are stored in a vacuum flask, it is important to keep the stopper in the flask. Why is it less important to have a stopper in a flask that is being used to keep things cold $?$

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Physics Coursebook Second Edition>Chapter 11 - Thermal (Heat) Energy Transfers>End-of-chapter questions>Q 10

Some water in a glass beaker is heated from below, as shown in the diagram.

Question Image