how heat and work affect each other

2. What is this thing which
you call as HEAT?

3. Heat is form of energy
Heat is transferred from a body at a higher
temperature to a body at lower temperature.
Simply means the transfer of energy
from a hot object to a colder object.
Heat energy is also known as thermal energy
Who is the first person
experimented the nature of
heat?
Who is the first person
experimented the nature of
heat?

4. BENJAMIN THOMPSONBENJAMIN THOMPSON
- Also known as COUNT RUMFORD
- In 1798, he first experimented the nature of
HEAT
- In 1798, he first experimented the nature of
HEAT
- While supervising the “boring of brass cannon”,
he observed that a tremendous amount of heat
was generated in the process.
- While supervising the “boring of brass cannon”,
he observed that a tremendous amount of heat
was generated in the process.
- He immersed the cannon in a container of
water and observed that the water near the
cannon is boiling.
- He suggested that there must be a relationship
between the amount of heat generated and the
mechanical work done.

5. Can we sayCan we say
that Work canthat Work can
produce Heat?produce Heat?

6. MECHANICALMECHANICAL
EQUIVALENT OF HEATEQUIVALENT OF HEAT
JAMES PRESCOTT JOULEJAMES PRESCOTT JOULE
In 1845, he experimentally determined the
mechanical work needed to produce a given
amount of heat.
Fig.18.1. James Joule’s paddle wheel apparatus
for determining mechanical equivalent of heat.
It consist of a falling mass that turns paddle
resulting in an increase in temperature of water.

7. James Joule has shown that MechanicalJames Joule has shown that Mechanical
energy can produce heat and that they areenergy can produce heat and that they are
related to each other as follows:related to each other as follows:
W= JHW= JH
where,where, W = Mechanical Energy or WorkW = Mechanical Energy or Work
in Joulein Joule
H= Heat developed in CaloriesH= Heat developed in Calories
J = mechanical equivalent of heatJ = mechanical equivalent of heat
( J= 4.186 Joules/calorie)( J= 4.186 Joules/calorie)

8. Sample ProblemSample Problem
A simple demonstration that work can beA simple demonstration that work can be
transformed into heat is by rubbing your handtransformed into heat is by rubbing your hand
together to warm them up. Suppose that intogether to warm them up. Suppose that in
rubbing your hands you perform 4500J ofrubbing your hands you perform 4500J of
work against friction A) How much heat inwork against friction A) How much heat in
calories did you generate? B) By how muchcalories did you generate? B) By how much
will the temperature of your hands change?will the temperature of your hands change?
Assume that your hands have a combinedAssume that your hands have a combined
mass of 1.50 kg and that the specific heat ofmass of 1.50 kg and that the specific heat of
the hands is 0.83 cal/g ºCthe hands is 0.83 cal/g ºC

9. A simple demonstration that work can be transformed into heat is by
rubbing your hand together to warm them up. Suppose that in rubbing
your hands you perform 4500J of work against friction A) How much heat
in calories did you generate? B) By how much will the temperature of
your hands change? Assume that your hands have a combined mass of
1.50 kg and that the specific heat of the hands is 0.83 cal/g ºC
GIIVEN:
W = 4500 J
m = 1.50 kg
c = 0.83 cal/gºC

10. where, m = mass
c = specific heat
tf and ti = final and initial temperature
Recall:
“Heat is needed to change the temperature of a substance is given
by the equation
H = mc (tf - ti )H = mc (tf - ti )

11. A. W = JH
4500 J = 4186 J/calorie (H)
H = 1075 calories
SOLUTION:
B.H = mc (tf - ti )

12. Exercise 18.1
A 52.0 g Aluminum calorimeter
contains 175.0 g water at 25ºC. You
continuously stir the water and found out
that the temperature of water has risen to
25.3 ºC. How many J of work did you do
in stirring the water? Neglect the heat
absorbed by water.

13. James Joule showed that the
process of doing work
produces/released heat. Do you
think the reverse is possible?
That is, can heat do work?
LET’S WATCH THIS!

14. THERMODYNAMICSTHERMODYNAMICS
-Literally means “movement of heat”
- The study of heat and its
transformation to mechanical
energy and vice versa.
However, in the course of time, it
encompasses the whole field of the
transformation of energy between all the
forms in which it may be manifested –
thermal, mechanical, electrical, chemical
or radiant.

15. A device that converts heat energy to mechanical work.
HEAT ENGINESHEAT ENGINES
It takes many forms, from the internal combustion engines in our
cars to the giant turbines that generate electricity for our homes.
All heat engines make use of a substance inside them that
undergoes cooling and/or heating, compression and/or
expansion and sometimes change of phase. This substance
is called the working substance of the engine.
For example, the working substance in a stream engine is water.
For gasoline engine is gasoline – air mixture.

16. CLASSIFICATION OF HEAT
ENGINE
INTERNAL COMBUSTION ENGINEINTERNAL COMBUSTION ENGINE
-Burns fuel inside the engine
-Example: gasoline engine and diesel engine
EXTERNAL COMBUSTION ENGINEEXTERNAL COMBUSTION ENGINE
-Burns fuel outside the engine
-Example: steam engine

17. Oldest heat engine
Invented by Hero of Alexandria in 200
BBC
He called it “aeolipile” in which steam was conducted
through pipes from a boiler. The steam caused a sphere to
rotate.
Hero’s steam engine is intended to
be a toy only.

18. PILLAR OF SCIENCE
RUDOLF CHRISTIAN KARL DIESEL (1858 – 1913)RUDOLF CHRISTIAN KARL DIESEL (1858 – 1913)
-German engineer who invented and received a patent
for his heat – driven oil engine, now called the diesel
engine in 1892.
-- He powered up the first working diesel engine by
peanut oil on August 10, 1893.
- Today, diesel engine are used in cars, trucks, trains,
electric power generation, factories, farm machinery,
mining and oil drilling apparatus.

19. TEST YOURSELF
DIRECTION: Identify the following.
1. It is also known as thermal energy.
2. He said that heat can do work.
3. He is the one that first experimented on the nature of heat.
4. It is the unit of heat.
5. It is the unit for work.
6. He is the German Engineer who first invented the heat
driven oil engine.
7. One of the classification of heat engines that happening in a
car engine.
8. It is the invention of Hero of Alexandria.
9. It literally means movement of heat.
10. It is the working substance of steam engine.
.