Question

Write a short note on following
1)The construction of an electroscope
2)modes of heat transfer
3) Thermos flask with diagram​

Answer 1

Answer:

1)CONSTRUCTION OF AN ELECTROSCOPE : An electroscope consists of a metal rod with a knob at the top and a pair of thin metal leaves at the bottom. The rod is inserted in a one hole rubber stopper which fits into a flask. The flask contains the lower part of the rod and the metal leaves. 2)Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heat transfer.

Answer 2

Answer:

ANSWER

In a thermos flask ,

(a) a thin layer of vacuum is provided between the two walls of flask, to minimise the heat loss by conduction , because for conduction medium (molecules) is required , but now medium is absent .

.(b) the two walls are silvered to minimise the heat loss by radiation , because a shiny surface is a bad absorber and bad emitter of radiation i.e. good reflector of heat , so prevents the heat exchange between content of flask and surrounding .

(c) the lid of flask is provided with a tight cork stopper to minimise the heat loss by convection , so that convection currents cannot go out .

(d) a plastic (or metal) case is provided with a flask , to protect the flask from physical damage .

An electroscope is a scientific device that is used to detect the presence of an electric charge on a body. In the year 1600, British physician William Gilbert invented the first electroscope with a pivoted needle called versorium.

Electroscope detects the charge based on the Coulomb electrostatic force which causes the motion of test charge. Electroscope can be regarded as a crude voltmeter as the electric charge of an object is equal to its capacitance. An instrument that is used to measure the charge quantitatively is known as an electrometer.

An electroscope consists of a metal rod with a knob at the top and a pair of thin metal leaves at the bottom. The rod is inserted in a one hole rubber stopper which fits into a flask. The flask contains the lower part of the rod and the metal leaves

Explanation:

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