This document defines and compares various units of energy and power, including joules, calories, British thermal units (Btus), horsepower, and watts. It provides conversion factors between units and explains concepts like one calorie being the energy to raise one gram of water by 1°C. Tonnage ratings for air conditioners are also covered, with one ton of refrigeration being defined as melting one ton of ice in 24 hours. Prefixes for watts as SI multiples and submultiples are also included.

1. Lecture – 12.08.2014
By
P. Kanthasamy
Principal Technical Officer
Environmental Technology Division
CSIR- Central Leather Research Institute
Adyar, Chennai-600 020
Email:samyji@gmail.com Mobile:9445587722

2. Definitions of UNITS
• Joules
• Calories
• Btu
• Horse power
• Conversion of Centigrade to Fahrenheit and
vice versa
• Ton ( TR-Ton Rating)
• Prefix for Power in Watts

3. SI Units
Quantity SI-unit Alternative units
Time s (second) h (hour)
Length m (meter) in (inch)
ft (foot)
Mass kg (kilogram) lb (pound)
Temperature K (Kelvin) °C (Celsius)
°F (Fahrenheit)
Force N (Newton) kp (kilopond)
Pressure Pa (Pascal) = N/m2 bar
atm (atmosphere)
mm Hg (millimeter mercury column)
psi (pound per square inch)
Energy J (Joule) = Nm kWh (kilowatt hour)
cal (calorie)
Btu (British thermal unit)
Power W (Watt) = J/s calorie/h, Btu/h

4. Pound conversion
• 1Kg=2.2046 pounds
• 1pound=.04536 kg
• 1pound= 16 ounce
• 1 ounce= 29.5735ml=28.3495 gms
• 1 cubic meter is equal to 33814.0225589 oz, or 1000000 ml.
• 1 Cubic metre=1000litres
• The number of fluid ounces which equal a pound depend on the type
of liquid being measured.
• Liquids have different densities, a factor which affects how much the
fluid weighs. For example, sixteen fluid ounces of water weighs 1.043
pounds and one fluid ounce of milk weighs 1/16th of a pound.
• Pounds are a measuring unit used to measure weight and fluid
ounces are a unit used to measure volume. The fluid ounce is used in
the imperial measuring system.

5. What is a Joule ?
1 N
1m
1 N
• 1 Joule = 1Nm
• Joule is SI unit of work or energy, equal to the
work done by a force of one newton when its
point of application moves one metre in the
direction of action of the force, equivalent to
one 3600th of a watt-hour.

6. Joule –Cont.
• One joule per second equals 1 watt
or
• 0.737 foot pounds,
or
• 9.47 x 10^-4 British thermal units (Btu) (one Btu equals
about 1,055 joules).
• It equals about 0.24 calories, or roughly the energy
required to raise a spoonful of food to mouth.
• Named after UK physicist James Prescott Joule (1818-
89) who in 1843 discovered the mechanical
equivalent of heat.

7. One Calorie
1kcal =4.187 kJoules

8. Calorie
• One Calorie is the amount of heat required to raise
the temperature of one gram of water by 1°C.
• It equals 4.18 joules or about 0.004British thermal
units (Btu). Also called gram calorie or small calorie.
• Unit of energy-producing potential of food (commonly
shown as calorie on the nutrition label of the item) is
actually a kilocalorie equal to 1,000 small calories
amount of heat required to raise the temperature of
one kilogram of water by 1°C.
• It equals 4.18 kilojoules or about 4 British thermal units
(Btus). Also called food calorie, kilogram calorie, large
calorie, or nutrition calorie.

9. British Thermal Unit (Btu)
• A BTU (British Thermal Unit) is the amount of heat
necessary to raise one pound of water by 1 degree
Farenheit (F).
1 British Thermal Unit (BTU) = 1055 J (The Mechanical
Equivalent of Heat Relation)
1 BTU = 252 cal = 1.055 kJ
1 Quad = 1015 BTU (World energy usage is about 300
Quads/year, US is about 100 Quads/year in 1996.)
1 therm = 100,000 BTU
1,000 kWh = 3.41 million BTU
Power Conversion
• 1 horsepower (hp) = 745.7 watts

10. Btu –contd.
• This is the standard measurement used to state the
amount of energy that a fuel has as well as the
amount of output of any heat generating device.
• You might be able to imagine it this way. Take one
gallon (8 pounds) of water and put it on your stove.
If the water is 60 degrees F and you want to bring it
to a boil (212 degrees F.) then you will need about
1,200 BTUs to do this.

11. Btu-contd.
• One 1Btu= 252 small calories or 0.252 kilocalories,
• 1 Btu=778.17 foot pounds, or 1055.06 joules.
• 1 kWh=3412 BTUs
• One pound of air-dried wood generates about 7,000 Btu,
• a gallon of liquid propane (a hydrocarbon) about 92,000 Btu,
One Gallon=3.78541 (US gallon)
• a gallon of fuel-oil about 140,000 Btu, one barrel of gasoline about
5.25 million Btus,
• One barrel= 159 litres approximately=42 Gallons
• an average ton of coal about 20 million Btu
• one kilowatt-hour of electricity about 3,400 Btu.
Used also as a unit of measurement for natural gas prices (1,034 Btu
= 1 cubic-foot of natural gas).
• One Btu per hour equals 0.293 watt and is represented by
the symbol Btu/h (not Btuh).

12. Btu –contd.
• MBTU stands for one million BTUs, which can also be
expressed as one decatherm (10 therms). MBTU is
occasionally used as a standard unit of measurement
for natural gas and provides a convenient basis for
comparing the energy content of various grades of
natural gas and other fuels.
• One cubic foot of natural gas produces approximately
1,000 BTUs, so 1,000 cu.ft. of gas is comparable to 1
MBTU. MBTU is occasionally expressed as MMBTU,
which is intended to represent a thousand thousand
BTUs.

13. Power
• Power is defined as the rate at which work is done
upon an object.
• Like all rate quantities, power is a time-based
quantity. Power is related to how fast a job is
done. Two identical jobs or tasks can be done at
different rates - one slowly or and one rapidly. The
work is the same in each case (since they are
identical jobs) but the power is different. The
equation for power shows the importance of
time:
• Power = Work / time
• P = W / t

14. What is horsepower?
The story goes that Watt was
working with ponies lifting coal at a
coal mine, and he wanted a way to
talk about the power available from
one of these animals.
He found that, on average, a mine
pony could do 22,000 foot-pounds
of work in a minute.
He then increased that number by
50 percent and pegged the
measurement of horsepower at
33,000 foot-pounds of work in one
minute.

15. Horse Power
What horsepower means is this:
In Watt's judgement,
• one horse can do 33,000 foot-pounds of work every
minute.
So, imagine a horse raising coal out of a coal mine as
shown above.
• A horse exerting 1 horsepower can raise 330 pounds
of coal 100 feet in a minute,
• or 33 pounds of coal 1,000 feet in one minute,
• or 1,000 pounds 33 feet in one minute.
You can make up whatever combination of feet and
pounds you like. As long as the product is 33,000 foot-pounds
in one minute, you have a horsepower.

16. Conversion of Horsepower
Horsepower can be converted into other units as well. For
example:
• 1 horsepower is equivalent to 746 watts. So if you took
a 1-horsepower horse and put it on a treadmill, it could
operate a generator producing a continuous 746 watts.
• 1 horsepower (over the course of an hour) is equivalent
to 2,545 BTU (British thermal units).
• If you took that 746 watts and ran it through an electric
heater for an hour, it would produce 2,545 BTU
• One BTU is equal to 1,055 joules, or 252 gram-calories
or 0.252 food Calories. Presumably, a horse producing 1
horsepower would burn 641 Calories in one hour if it
were 100-percent efficient.

17. Prefix for Power in Watts
SI multiples for watt (W)
Submultiples Multiples
Value Symbol Name Value Symbol Name
−1
W dW deciwatt 10
10
1
W daW decawatt
−2
W cW centiwatt 10
10
2
W hW hectowatt
−3
W mW milliwatt 10
10
3
W kW kilowatt
−6
W μW microwatt 10
10
6
W MW megawatt
−9
W nW nanowatt 10
10
9
W GW gigawatt
−12
10
12
W TW terawatt
W pW picowatt 10
−15
10
15
W PW petawatt
W fW femtowatt 10
−18
10
18
W EW exawatt
W aW attowatt 10
−21
10
21
W ZW zettawatt
W zW zeptowatt 10
−24
10
24
W YW yottawatt
W yW yoctowatt 10
Common multiples are in bold face

18. Conversion of Centigrade to
Fahrenheit and vice versa
• Degree Fahrenheit = (1.8xDegree centigrade)+32
• 1degree Centigrade = (Fahreheit-32)/1.8
30degree centigrade is how many Fahrenheit?
Fahrenheit = (30 x 1.8 ) +32= 86 Degree
100 Degree Fahrenheit is how many deg. Centigrade?
Centigrade= (100-32)/1.8=37.7778

19. 1 Ton Rating AC
• A Ton of refrigeration (RT) is a unit of power
used to describe the heat-extraction capacity
of air conditioning and refrigeration
equipments.
• It is defined as the heat of fusion absorbed by
melting 1 short ton of pure ice at 0 °C (32 °F)
in 24 hours.
• 1Ton=1000kCals=4127kilojoules-12000 Btu/hr

20. Conversion of Units
• How many kW and HP are there in 1 Ton?
• 1 Ton = 3.5168525 kW = 4.714Hp
• Explanation
• 1 Ton = 12,000 BTU/h
1 Watt = 3.412141633 BTU/h
• 1 Ton = 12,000 / 3.412141633 = 3,516.8528 Watts
=3.5168528 kW.
• 1 Ton = 3,516.8528 Watts = 3.516 kW.
• Also
• 1 Ton = 3,516.8528W / 746 = 4.7142798928 Hp →→→
(1 Hp = 746 Watts)
• 1 Ton = 4.714 Hp

21. 1 Ton AC
• Quantity of heat is termed in Tons means if an air
conditioner is able to remove 1000 kilocalories of
heat
or 4120 kilojoules or 12000 BTU of heat in an hour that
AC rated as 1Ton of AC
because 1000 Kilocalories or 4120 kilojoules or 12000
BTU equal to one Ton of heat.
• 1Ton Ac= Removing heat at the rate of 12000 Btu/hr
• if you have a ton of ice, it takes (143 BTU/lb) x (2000
lbs) = 286,000 BTUs to melt it completely in 24 hrs.
=286000Btu/24hrs=11916.66667=11917 Btu/hr

22. Hyundai i10 Engine
• Fuel type : Gasoline
• Displacement : 1,086 cc
• Max. Power : 69 ps / 5,500 rpm
• PS stands for pferdestarke.
• Most common car power is measured in PS & BHP(break horse
power)...BHP & PS are two measures adopted by two different standard
agencies.
• 1BHP=.986PS
• & 1BHP=745watts
• Max. Torque : 10.1 kg·m / 4,500 rpm
•
• The i10 has three engines to choose from, a 1.1ℓ with 69 ps, the 1.25ℓ with
87 ps, and the 1.0ℓ with 69 ps.
• Constantly Variable Valve Technology (CVVT), which measures every drop of
fuel for maximum efficiency is available on the 1.25. These engines not only
deliver exceptional fuel economy, they give really low emissions.

23. Summary of Units
• Energy Units and Conversions
• 1 Joule (J) is the energy, equal to the force of one Newton acting through
one meter.
•
1 Watt is the power of a Joule of energy per second
•
Power = Current x Voltage (P = I V)
•
1 Watt is the power from a current of 1 Ampere flowing through 1 Volt.
• 1 kilowatt is a thousand Watts.
1 kilowatt-hour is the energy of one kilowatt power flowing for one hour.
(E = P t).
1 kilowatt-hour (kWh) = 3.6 x 106 J = 3.6 million Joules
• 1 calorie of heat is the amount needed to raise 1 gram of water 1 degree
Centigrade.
1 calorie (cal) = 4.184 J
(The Calories in food ratings are actually kilocalories.)

24. Problems
1. When doing a chin-up, a physics student lifts her 42.0-kg body a distance of
0.25 meters in 2 seconds. What is the power delivered by the student's
biceps?
2. Your household's monthly electric bill is often expressed in kilowatt-hours.
One kilowatt-hour is the amount of energy delivered by the flow of 1
kilowatt of electricity for one hour. Use conversion factors to show how
many joules of energy you get when you buy 1 kilowatt-hour of electricity.
3. An escalator is used to move 20 passengers every minute from the first
floor of a department store to the second. The second floor is located 5.20
meters above the first floor. The average passenger's mass is 54.9 kg.
Determine the power requirement of the escalator in order to move this
number of passengers in this amount of time.

25. Answer for Question.1
• To raise her body upward at a constant speed,
the student must apply a force which is equal
to her weight (m•g). The work done to lift her
body is
• W = F * d = (411.6 N) * (0.250 m)W = 102.9 J
• The power is the work/time ratio which is
(102.9 J) / (2 seconds) = 51.5 Watts (rounded)

26. Q. An escalator is used to move 20 passengers every minute from the first floor of a department
store to the second. The second floor is located 5.20 meters above the first floor. The average
passenger's mass is 54.9 kg. Determine the power requirement of the escalator in order to move
this number of passengers in this amount of time.
Question 3
Answer:
A good strategy would involve determining the work required to elevate one
average passenger. Then multiply this value by 20 to determine the total work
for elevating 20 passengers. Finally, the power can be determined by dividing
this total work value by the time required to do the work. The solution goes
as follows:
W1 passenger = F • d • cos(0 deg)
W1 passenger = (54.9 kg • 9.8 m/s2) • 5.20 m = 2798 J (rounded)
W20 passengers = 55954 J (rounded)
P = W20 passengers / time = (55954 J) / (60 s)
P = 933 W

27. Question No.2
Your household's monthly electric bill is often expressed in kilowatt-hours. One kilowatt-hour is the amount of
energy delivered by the flow of 1 kilowatt of electricity for one hour. Use conversion factors to show how many
joules of energy you get when you buy 1 kilowatt-hour of electricity.
Answer:
• Using conversion factors, it can be shown that
• 1 kilo-watt*hour is equivalent to 3.6 x 106 Joules.
• First, convert 1 kW-hr to 1000 Watt-hours.
• Then convert 1000 Watt-hours to 3.6 x 106 Watt-seconds.
Since a Watt-second is equivalent to a Joule.

28. Thank You

29. New Things to learn
• CD- Compact Disc
• DVD-Digital -Digital Versatile Disc
• USB- Universal Serial Bus

30. Definition of USB
• Universal Serial Bus (USB)
• Abbreviated as USB, Universal Serial Bus is a
standard type of connection for many
different kinds of devices.
Tip: The male connector on the cable
or flash drive is typically called
the plug. The female connector on the
device, computer, or extension cable is
typically called the receptacle.
receptacle

31. USB Version
• There have been three major USB standards, 3.0 being the
newest:
• USB 3.0: Called SuperSpeed USB, USB 3.0 compliant hardware
can reach a maximum transmission rate of 5 Gbps (5,120
Mbps).
• A planned update to the USB 3.0 standard will increase the
maximum data rate to 10 Gbps (10,240 Mbps), matching that
of Thunderbolt, a potential replacement for USB.
• USB 2.0: Called High-Speed USB, USB 2.0 compliant devices
can reach a maximum transmission rate of 480 Mbps.
• USB 1.1: Called Full Speed USB, USB 1.1 devices can reach a
maximum transmission rate of 12 Mbps.
• Most USB devices and cables today adhere to USB 2.0, and a
growing number to USB 3.0.