Vacum flask has inner layer of glass and outer body of plastic.the glass has a reflective metal layer..when a hot drink is poured into the flask it prevents conduction.tight lid stops the convection.when radiation tries to leave the hot drink the reflective layer of the glass reflects it back so no heat can escape.
Answer:
Ratio of magnetic field will be 
Explanation:
We have given radius of the loop r = 30 mm = 0.03 m
We know that magnetic field at the center of the loop is given by
---------eqn 1
Number of turns in the solenoid is given as n = 3 turn per mm = 3000 turn per meter
We know that magnetic field due to solenoid is given by
-------------eqn 2
Now dividing eqn 1 by eqn 2
Answer:
Length is the unit of metre
Countries longer day for example in the Middle East could benefit more but Alaska has more night like longer night which is why it would hard to benefit from the solar panels there.
Hoped this helped
