Chapter 3
Energy
3.1
Energy Exists in Different Forms
3.2
Energy Can Change Forms But is Never Lost
3.3
Technology improves the ways people use
Energy
3.2 Energy can change forms but is never lost
A. Energy changes forms
1. Ex: Plants change sunlight
(electromagnetic energy)
to sugar (chemical energy)
then we eat the sugar and
change it to heat(thermal)
and motion(mechanical).
3.2 Energy can change forms but is never lost
A. Energy changes forms
2. PE turns into KE
a) he is at the top, this
position gives him PE, but
he is not moving, so no KE
b) As he moves down the hill
his PE turns into KE
c) at the bottom of the hill his
position does not give him
PE, but he is moving fast,
so he has KE
PE
PE
PE
KE
KE
3.2 Energy can change forms but is never lost
A. Energy changes forms
3. Ex: water and a dam
1st: water behind dam is high: PE
2nd: Water falls through pipe: PEKE
3rd: moving water moves turbine:
KEKE
4th: moving turbine turns generator:
KEKE
5th:Moving generator makes electricity:
KE  Electricity
3.2 Energy can change forms but is never lost
Energy changes forms Classwork
Draw your own picture or comic
showing at least 4 changes in
energy
PE
PE
PE
KE
KE
3.2 Energy can change forms but is never lost
3.2 Energy can change forms but is never lost
B. Energy is always conserved:
1. The law of conservation of energy states that energy can neither
be created nor destroyed.
2. The amount of energy you start out with is the same amount of
energy you end up with.
3. Only the forms of energy change
3.2 Energy can change forms but is never lost
C. Energy conversions may produce
unwanted forms of energy
1. Energy efficiency is the amount of
useful energy you get from a system.
2. most energy transformations are not
very efficient
3. Energy can be wasted, usually as heat.
a) Ex: a car engine changes chemical
energy to motion(KE) but a lot is
wasted as heat
b) Ex: efficient light bulbs waste less
heat