Thermal Energy Transfer

Question 1

What is Thermal Energy Transfer?

Answer 1

There are 3 methods for thermal energy to flow. Which are: Conductivity, convection, and radiation

Question 2

Define conduction + the mechanisms contributing to conduction

Answer 2

This method works in all phases (solid, liquid, gas) but faster in solid phase as the molecules are so closer together.
There are 2 mechanisms contributing to conduction:
1st. Free electrons- As these are in the outer shell of an atom, there is the least bound between them to the nucleus, so they leave the atom easily to carry thermal energy.
2nd. Ionic Vibration- Each ion can vibrate about its’ equilibrium position and the vibration of each ion is transferred to the adjacent one.

Question 3

Define convection and its’ examples

Answer 3

Convection works in fluids (gas or liquid) not solid. In this method, a group of atoms move to transfer thermal energy.
Ex; On-shore and Off-shore
On-shore: During the day, air above land is warmer compared to air above sea due to high specific heat capacity of water. Therefore, air above land goes up and air above sea is replaced as it’s heavier. So during the day, the breeze is being blown from the sea to the land.

Off-shore: At night, air above sea is warmer, so it is lighter to go up. As the air above land is colder and heavier, wind is blown from the land to the sea.

Question 4

Define radiation

Answer 4

Based on electromagnetic waves, thermal energy is transferred from the sun to the Earth, Also, electromagnetic waves don’t need a medium to go through, so this is the fastest way to transfer thermal energy.

Question 5

Point about radiation:

Answer 5

All bodies radiate. The objects which have the most amount of radiation are called black bodies (as they absorb all the wave lengths, so they emit or radiate all the wave length).
At the other side, the objects which have the least amount of radiation are called white bodies (as they reflect all the incident energy).
On the left side of the spectrum there are the white bodies and at the right side there are the black bodies.

Question 6

How can we make a black body?

Answer 6

There is an in-closed container (cavity), and a small whole is made on its’ wall. The light ray is incident through that small hole into the cavity. As the interior of the cavity is painted in Matt black, it absorbs all the wave lengths. So, all the wave lengths are radiated either. So the light cannot come out of the cavity, making this process infinite.