Question

Q No. 16.
Things remain hot for longer time in a thermos bottle because:
a) air between the two walls of the thermos flask is evacuated
b) walls of thermos bottle are made up of steel
c) walls of the thermos bottle are made up of glass
d) walls of thermos bottle are good conductor
کیونکہ
سے ہوا کو خالی کرالیا جاتا ہے
میں سٹیل کی بنی ہوتی ہیں
- میں کلاس کی بنی ہوتی ہیں
میں اچھی موصل ہوتی ہیں

Answer 1

Answer:

option a...

hope this helps you...

Answer 2

BECAUSE:walls of thermos bottle are made up of steel

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 .