lesson 10- energy efficiency

Question 1

systems

Answer 1

the particular item of study

Question 2

surroundings

Answer 2

everything else around it

Question 3

calculation for systems and surroundings

Answer 3

system + surroundings = universe

Question 4

open system

Answer 4

matter and energy can be exchanged in and out (eg. earth)

Question 5

closed system

Answer 5

only energy can be exchanged (eg. closed container)

Question 6

isolated system

Answer 6

neither matter or energy can be exchanged (e.g. thermos)

Question 7

first law of thermodynamics states that

Answer 7

energy cannot be created or destroyed, just transformed and efficiency is a measure of how much input energy is transformed into useful output energy

Question 8

efficiency formula

Answer 8

E = useful output energy/ total input energy x 100

Question 9

second law of thermodynamics states that

Answer 9

heat always flows from a hot object to a cold object

Question 10

heat engine

Answer 10

uses law to convert heat flow into mechanical energy

Question 11

heat pump

Answer 11

device that transfers heat from a colder area to a warmer area using mechanical energy

Question 12

why are machines not 100% efficient?

Answer 12

because they lose their efficiency due to friction