Topic 4 - Transfer By Heating

Question 1

how can energy be transferred by heating?

Answer 1

radiation, conduction or convection

Question 2

what is thermal radiation?

Answer 2

the transfer of energy by heating by infrared electromagnetic waves

Question 3

what do conduction and convection involve?

Answer 3

transfer of energy by particles

Question 4

conduction is the main form of energy transfer by heating in…

Answer 4

solids

Question 5

Convection is the main form of energy transfer by heating in…

Answer 5

liquids and gases

Question 6

how does temperature difference affect the speed of thermal radiation?

Answer 6

the larger the temperature difference, the faster energy is transferred between the thermal energy stores of a body and its surroundings

Question 7

what can thermal radiation also be called?

Answer 7

infrared (IR) radiation

Question 8

how does temperature affect how much IR radiation an object emits?

Answer 8

a hotter object emits more IR radiation than it absorbs. cooler objects do the opposite.

Question 9

what is thermal conduction?

Answer 9

thermal conduction is the process where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of neighbouring particles.

Question 10

how does conduction heat an object?

Answer 10

objects in one part of a solid are heated and start to vibrate. vibrations pass from particle to particle through the solid. gradually some energy is passed through the solid, causing the temperature of the other side to rise.

Question 11

how would you do an experiment to demonstrate conduction?

Answer 11

1. attach beads at regular intervals to one-half of a long metal bar using wax
2. hold the middle of the bar in a clamp stand. heat the side without the beads using a Bunsen burner
3. as time goes on, the wax holding the beads will melt. the bead closes to the bunsen will melt first, demonstrating conduction

Question 12

how do you reduce energy transfer away by conduction?

Answer 12

use a material with low thermal conductivity

Question 13

how do you reduce energy transfer away by convection?

Answer 13

stop the fluid moving, preventing convection current from forming

Question 14

how does insulation reduce energy transfer?

Answer 14

pockets of air are trapped and can’t move, so energy has to conduct very slowly through the air pockets and the material in between, both of which have low thermal conductivity

Question 15

which colours and surfaces absorb and emit IR radiation the best?

Answer 15

matt and black surfaces

Question 16

which colours and surfaces absorb and emit IR radiation the worst?

Answer 16

shiny and white surfaces

Question 17

how does a Leslie cube demonstrate IR emission changing based on surfaces?

Answer 17

A Leslie cube filled with water will emit different amounts of IR radiation from each face, although every face is the same temperature.