Energy stores and conservation & dissipation

Question 1

Total energy of a system must remain….

Answer 1

Constant but can be transferred to one type of energy to another.

Question 2

What is an example of “wasted” energy?

Answer 2

Heat given off by a light bulb, this is usually due to friction where kinetic energy is then turned into thermal.

Question 3

What does all energy used, also end up as?

Answer 3

Thermal energy, difficult to turn into useful energy.

Question 4

Transfers of energy can never be 100% …….?

Answer 4

Efficient

Question 5

How to calculate efficiency of a device?

Answer 5

Useful energy output/ total energy input.

usually x by 100 to get answer as a percentage!!!!

Question 6

What is a substance called that won’t allow thermal energy through it?

Answer 6

An insulator.

Question 7

How can you insulate your house for example?

Answer 7

Using foil to prevent infrared from escaping. Also double glazed windows as there is a gap in between filled with a vacuum or gas which prevents transfer of thermal energy.

Question 8

Describe the changes in energy stores as a car breaks to stop the car

Answer 8

The energy transfers from the car’s kinetic energy store to the thermal store of the breaks.

Question 9

Define energy dissipation

Answer 9

the transfer of energy to a store where it cannot be retrieved