Conservation and dissipation of energy (1.2) (M)

Question 1

What is the conservation of energy?

Answer 1

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

Question 2

What is the net change in total energy after a transfer in a closed system?

Answer 2

there is no net change

Question 3

What happens in (non-closed) system changes to energy?

Answer 3

energy is dissipated/wasted, so that it is stored in less useful ways

Question 4

2 ways

How can you reduce unwanted energy transfers?

Answer 4

lubrication and thermal insulation

it rhymes, so try to remember it that way

Question 5

The higher the thermal conductivity of a material the (…) the rate of energy transfer by conduction across the material

Answer 5

higher

Question 6

What is the problem with substances with a high thermal conductivity?

Answer 6

They let lots of heat flow through it quickly (more energy dissipated)

Question 7

Why is energy dissipated if anything is moving along a surface? What substance could you use to stop this?

Answer 7

If anything is moving, then friction is shifting energy from work done by forces.

Lube is useful (or other lubricant)

Question 8

What happen to the rate of cooling of a building if it has thick walls?

Answer 8

Rate of cooling will decrease with increased thickness/less thermal conductivity

Question 9

What happen to the rate of cooling of a building if it has thinner walls?

Answer 9

rate of cooling will increase with increased thermal conductivity/thicker walls

Question 10

The greater the change (decrease) in temperature, more energy is…

Answer 10

dissipated/wasted

Question 11

How would you increase the efficiency of an intended energy transfer?

Answer 11

lubrication and thermal insulation

Question 12

What is efficiency?

Answer 12

A measure of how useful a substance is at transferring energy

may be power as well

Question 13

What type of radiation is infrared radiation?

Answer 13

electromagnetic radiation - involves waves

Question 14

Why can we still feel the heat of the Sun even though it is so far away?

Answer 14

Infrared radiation is an electromagnetic radiation (involves waves), that does not need particles

So infrared radiation from the sun can travel through the vacuum of space

Question 15

What are three ways in which heat can be transferred

Answer 15

• conduction
• convection
• radiation

Question 16

A heater is switched on, however after a period of time, the temperature of the room has become constant, even though the heater is still switched on. Explain why?

Answer 16

The room is losing energy/heat

at the same rate the heater supplies it

Question 17

What does more energy efficient mean?

Answer 17

higher percentage/proportion of energy is usefully transferred

Question 18

What are three ways companies generating electricity could reduce carbon dioxide emissions?

Answer 18

1. use (more) renewable energy sources
2. make power stations more efficient
3. carbon capture