True or false

Question

(i) Steel is better conductor of heat than bricks.
(ii) Radiations are ultrasonic waves.
(iii) Black body is having emissivity 2.
(iv) Natural convection do not need any external source for fluid flow.
(v) Fins cause increase in rate of heat transfer

Answer 1

1] True
2] False
3] False
4] True
5] True

Answer 2

explain thermal conductivity & give its variation in case of solids liquids & gases