PHYSICS [1 Mark Question Answer]

In winter the birds fluff their feathers in order to trap air in their feathers so that the air provides heat insulation to their body from the surroundings and keeps them warm and saves them from winter.

It is better to use two thin blankets to keep the body warm rather than using a single blanket of equal thickness because in between the two thin blankets there is more air trapped than in the single blanket of equal thickness so using two thin blankets better heat insulation is provided to the body from the surroundings and keep us warm

In winters, the human body covered with a blanket keeps warm because the blanket has air trapped in it which provide heat insulation to the body from the surroundings and keep us warm

The flask consists of double-walled glass containers with a vacuum between the walls A and B to prevent heat loss due to conduction and convection as a vacuum is the excellent insulator .to prevent heat loss by radiation, the inner side of the wall A and outer side of wall B is silvered. It has a narrow mouth which is closed by a non-conducting rubber stopper.

A wooden knob and a metal latch are both being at the same temperature but it feels colder to touch the latch because the metal is a good conductor and as soon as we touch it heat from our hand flows to the latch and we feel cold while on the other hand wood is a bad conductor of heat, the heat of our hand does not flow into it, therefore, it does not feel cold.

1 calorie = 4.2 joules.

Six's maximum and minimum thermometer is used in meteorology and horticulture.

Clinical thermometer is used to measure human body temperature

Laboratory thermometer is used to measure and observe the temperature of various chemical reactions.

The thermometer works on the principle that substances expand on heating and contract on cooling. So we use a thermometric substance which expands and contracts uniformly.

Yes, it is possible to boil water in a thin paper cup because when heated the heat in the paper cup is transferred to the water through convection and paper cup doesn't get sufficient heat to get burnt

1 calorie = 4.2 joules.

In cold countries, windows are provided with two glass panes because in between these two glass panes, a thin layer of air is present: air being a bad conductor obstructs the conduction of heat from the room to outside.

Wood is an insulator of heat.

Land becomes warmer than water during the day because water has more specific heat capacity so it absorbs the heat and heats up slowly but on the other hand land has less specific heat and it heats up faster than water.

Water is heated generally from below because water itself is a bad conductor of heat and the transfer of heat through convection take place vertically upwards

A ventilator is provided in a room because it helps in removing the hot air from the room and allows the fresh and cold air to come in.

Let the Coefficient of linear expansion be α
Coefficient of cubical expansion be γ
The relation between the is
γ= 3 α

Joule is the SI unit of heat.

Gaps are left in the railway tracks because the tracks gets heated during the day and as a result they increase in length. If the gaps are not provided, the railway line would buckle outward and may cause derailment.

There are three types of thermal expansion
(a). Linear expansion
(b). Superficial expansion
(c). Cubical expansion

A substance is made up of molecules arranged in a lattice. On heating, the molecules vibrate faster in the lattice and bump into each other harder. So the distance between the molecules increases thus expanding lattice. Thus, the substances expand on heating.

We should heat the neck of the bottle because due to heating the neck will expand and loosen the stopper stuck in the neck. In this way, we can easily remove the stopper from the bottle.

Two uses of bimetallic strip are
(a). As thermostat in electric iron
(b). As balance wheel in watches

Yes, heat is a form of energy

A bimetallic strip consists of two metal strips- one with high coefficient of expansion and the other with low coefficient of expansion.

Coefficient of Linear expansion is equal to the change in length of a rod of length 1m when its temperature rises by 1°C.

Linear expansion is the increase in length of a solid on heating.

The increase in size of a body on heating is called thermal expansion.

Three devices used to detect heat radiations are
(a). Blackened bulb thermometer
(b). Differential air thermo scope
(c). Thermopile

In cold countries, water pipes are covered with poor conductors because poor conductor prevents water from freezing and thus prevent these pipes from bursting.