Page 36 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

v Conduction is a mode of heat transfer between two solids or parts of the same solid at

different temperatures. When the solids or parts are in direct physical contact with each
other.

v The materials which allow heat to pass through them are called conductors of heat. For
example, aluminum, iron, copper, etc.
v Conduction involves transfer of energy from one particle to the adjoining particle, so it is

usually observed in solids.
v The materials which do not allow heat to pass through them are called poor conductors of

heat or insulators. For example, plastic, wood, etc.
v Conductors and insulators have great applications in daily life.

v The heat transfer in liquids and gases take place through the process of convection.
v Land breeze and sea breeze occur in coastal areas because of convection currents in the air.

v The cool air blowing from the sea towards the land and during the day is called sea breeze
whereas the flow of air from the land towards the sea is known as land breeze.
v Radiation is a process of heat transfer that does not require a medium. It is through this

process that the heat from the Sun reaches the Earth.
v The amount of heat radiated from the objects depends upon the temperature. Higher the

temperature, higher will be the radiation. The radiated heat travels in as straight line from
the source of heat.

v Objects with dark-coloured surfaces absorb more heat and reflect very little. On the other
hand, objects with light coloured surfaces reflect more heat & absorb very little.

v German physicist and instrument maker, Daniel Gabriel Fahrenheit, is credited with not
only the invention of the thermometer that uses mercury instead of alcohol to measure
high temperatures but also the Fahrenheit scale.

Exercise

A. Tick (3) the correct answer.

1. In solids, heat is transferred by the process of ..................... .
(a) Conduction (b) Convection (c) Radiation (d) None of these

Ans. (a)

2. When a wooden spoon is dipped in a cup of ice cream, its other end ..................... .
(a) Becomes cold by the process of convention

(b) Becomes hot by the process of conduction

(c) Does not become cold
(d) None of these

Ans. (c)

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