Coefficient of Thermal Expansion and their Importance.pptx
Applied Physics for engineers lecture_1-2.pdf
1. Physics for chemical engineers
Muhammad Ibrahim Khan
Assistant Professor
Department of Physics
CUI, Lahore Campus
2. • Roughly 2/3 of the time in class devoted to presentation of
material by instructor
• Interactive periods during lectures where students work
together on problems
1
an “ACT”
• Occasional demos to illustrate key concepts
Format of Lectures
3. Overview of Learning Activities
Learning in this course will be by:
• Attendance at lectures where material will be presented
and explained, and the subject will be illustrated with
demonstrations and examples (My lectures will be a mix
of PPT slides and White board!);
• Private study, working through the theory as presented
in lectures, texts and notes, and gaining practice at solving
conceptual and numerical problems;
• Completing tutorial questions designed to give further
practice in application of theory, and feedback on student
progress and understanding;
5. • No one’s perfect.
So we give lots of
partial credit.
• But you must say
what you’re doing!
Write a lot of text
in addition to
equations in your
homework and
quizzes.
6. The Importance of Attending lecture
In the past, Students
who have skipped a
lot of classes have
received very bad
grades
Conversely, Students
who’ve come to most
or all of the classes
nearly always receive
A’s and B’s.
7. Understanding the ideas of each lecture
requires the knowledge of the previous
lectures
If you keep up, you
won’t end up
looking like this
the night before the
quizzes!
8. Course Objectives
The students will learn the fundamentals of the following topics:
• Understand fundamental laws of electrostatics and magneto statics
• Understand to use Gauss’s law to calculate electric fields
• Verify Ohm’s Law for DC current and voltage, compute resistivity and
conductivity
• Understand how to use Ampere.s and Biot-Savart Law to calculate
magnetic fields
• Analyze simple circuits with resistors, capacitors, and inductors
• Apply Faraday’s Law in electromagnetic induction
• Gain understanding of basic theory and equation of electromagnetic
waves
• Get basic knowledge of plane wave propagation, Reflection, Refraction,
Diffraction and polarization, graphical method of mirrors and lenses
9. Course Contents
• Fundamentals Laws of electrostatics and magneto
statics
• Charge, Coulomb,s law, Gauss,s law and its
application, electric potential energy, electric
current, resistivity and conductivity, Ohm,s Law and
its application
• Magnetic properties of materials, the magntic field
B, magnetic force on a currrent, torque on a current
loop, ampere,s and Biot-Savart Law to calculate
magnetic field, emf, Faraday,s law
• Different topics of Optics
10. Course Resources
1. Class lectures
2. Text books*
3. WWW. (web)
• Fundamental of physics 9th Edition Halliday
Resnick and Walker
• Engineering Physics Theory and experiments (10th
edition) SK Srivastave
11. From where we will Start?
• Electric force and its applications and related
problems
• Electric Field
• Electric Current
• Eclectic field due to point charge
• Dipole in an eclectic field
12. What are we going to learn?
A road map
• Electric charge
➔ Electric force on other electric charges
➔ Electric field, and electric potential
• Moving electric charges : current
• Electronic circuit components: batteries, resistors, capacitors
• Electric currents ➔ Magnetic field
➔ Magnetic force on moving charges
• Time-varying magnetic field ➔ Electric Field
• More circuit components: inductors, AC circuits.
• Maxwell’s equations ➔ Electromagnetic waves ➔ light waves
• Geometrical Optics (light rays).
• Physical optics (light waves): interference, diffraction.
13. Describing Motion and Interactions
Position—where you are in space (L or meter)
Velocity—how fast position is changing with time (LT-1 or m/s)
Acceleration—how fast velocity is changing with time (LT-2 or m/s2)
Force— what is required to change to motion of a body (MLT-2 or kg-m/s2 or N)
Inertia (mass)— a measure of the force needed to change the motion of a body (M)
Energy—the potential for an object to do work. (ML2T-2 or kg m2/s2 or N-m or J)
Work is equal to the force applied times the distance moved. W = F d
Kinetic Energy is the energy associated with an object’s motion. KE=½ mv2
Potential Energy is the energy associated with an objects position.
Gravitational potential energy PEgravity=mgh
Spring potential energy PEapring= -kx
Momentum— the potential of an object to induce motion in another object (MLT-1 or kg-
m/s)
Angular Momentum and Rotational Energy— the equivalent constants of motion for
rotation (MT-1 or kg/s) and (MLT-2 or kg m/s2 or N)
Pressure— force divided by the area over which the force is applied (ML-1T-1 or kg/m-s
or N/m2 or Pa)0
15. Effects of Electric Charge
• Hair seems to have a mind of its own when combed on a dry
winter day.
• What causes the hairs to repel one another?
• Why does a piece of plastic refuse
to leave your hand after you peeled
it off a package?
• Why do you get a slight shock
after walking across carpet and
touching a light switch?
16. • All these phenomena involve different materials rubbing against
one another.
• Electrostatic effects can be demonstrated by rubbing plastic or glass
rods with different furs or fabrics.
• Small wads of dry, paperlike material called pith balls are light
enough to be strongly influenced by electrostatic forces.
• When a plastic rod, vigorously rubbed with cat fur, is brought near
the pith balls, at first the pith balls are attracted to the rod like bits of
iron to a magnet.
• After contacting the rod, the pith balls
dance away from the rod.
• They are now repelled by the rod and
also by each other.
Effects of Electric Charge
17. • A repulsive force must be acting between the two pith balls after
they have been in contact with the rod.
• Perhaps the balls have received something (call it electric charge) from the
rod that is responsible for the force we observe.
• This charge was somehow generated by rubbing the rod with the cat fur.
• The force that is exerted by one stationary charge on another is called the
electrostatic force.
Effects of Electric Charge
18. Electric Current
• An electric current is a flow of electric charge.
• In electric circuits this charge is often carried by
moving electrons in a wire
• It can also be carried by ions in an electrolyte or by both ions
and electrons such as in an ionised gas (plasma)
• The SI unit for measuring an electric current is the ampere
which is the flow of electric charge across a surface at the rate
of one coulomb per second. Electric current is measured using
a device called an ammeter
• Electric currents cause Joule heating, which creates light in incandescent
light bulbs. They also create magnetic fields, which are used in motors,
inductors and generators.
• The moving charged particles in an electric current are called charge
carriers. In metals, one or more electrons from each atom are loosely
bound to the atom, and can move freely about within the metal.
These conduction electrons are the charge carriers in metal conductors.
19. Current Density
• Current density, J, is the electric current per
unit area of cross section
• The current density vector is defined as
a vector whose magnitude is the electric
current per cross-sectional area at a given
point in space, its direction being that of
the motion of the charges at this point
• In SI units, the electric current density is
measured in amperes per square metre, IL-2
21. • Benjamin Franklin introduced
the names positive and negative for
the two types of charge.
• He also proposed that a single
fluid was being transferred
from one object to another
during charging.
• A positive charge resulted from
a surplus of the fluid, and a
negative charge resulted from
a shortage of the fluid.
• Franklin arbitrarily proposed
that the charge on a glass rod
when rubbed with silk be called
positive.
22. • Franklin’s model comes surprisingly
close to our modern view
• When objects are rubbed together,
electrons may be
transferred from one object
to the other.
• Electrons are small, negatively
charged particles present in all
atoms and, therefore, in all
materials.
• A negatively charged object has
a surplus of electrons, and a
positively charged object has a
shortage of electrons.
• The atomic or chemical properties
of materials dictate which way the
electrons flow when objects are
rubbed together.
23. Blue Flashes from a
Wintergreen LifeSaver
Indirect evidence for the attraction of charges with opposite
signs can be seen with a wintergreen LifeSaver (the candy
shaped in the form of a marine lifesaver).
If you adapt your eyes to darkness for about 15 minutes and
then have a friend chomp on a piece of the candy in the
darkness, you will see a faint blue flash from your friend’s
mouth with each chomp. Whenever a chomp breaks a sugar
crystal into pieces, each piece will probably end up with a
different number of electrons. Suppose a crystal breaks into
pieces A and B, with A ending up with more electrons on its
surface than B.
24. Blue Flashes from a
Wintergreen LifeSaver
• This means that B has positive ions (atoms that
lost electrons to A) on its surface. Because the
electrons on A are strongly attracted to the
positive ions on B, some of those electrons jump
across the gap between the pieces. As A and B
fall away from each other, air (primarily
nitrogen, N2) flows into the gap, and many of
the jumping electrons collide with nitrogen
molecules in the air, causing the molecules to
emit ultraviolet light. You cannot see this type
of light. However, the wintergreen molecules on
the surfaces of the candy pieces absorb the
ultraviolet light and then emit blue light, which
you can see—it is the blue light coming from
your friend’s mouth.
Two pieces of a wintergreen LifeSaver candy as they fall away from each
other. Electrons jumping from the negative surface of piece A to the
positive surface of piece B collide with nitrogen (N2) molecules in the air.
25. Charge is Quantized
• In Benjamin Franklin’s day, electric charge was thought to
be a continuous fluid—an idea that was useful for many
purposes
• However, we now know that fluids themselves, such as air
and water, are not continuous but are made up of atoms and
molecules; matter is discrete. Experiment shows that
“electrical fluid” is also not continuous but is made up of
multiples of a certain elementary charge.
• Any positive or negative charge q that can be detected can be
written as
q = ne, n=1,2,3, . . . , (1)
in which e, the elementary charge, has the approximate value
e = 1.602 * 10-19 C (2)
26. Charge is Quantized
• The elementary charge e is one of the important constants of
nature
• The electron and proton both have a charge of magnitude e (Table
1). (Quarks, the constituent particles of protons and neutrons,
have charges of e/3 or 2e/3, but they apparently cannot be
detected individually
• For this and for historical reasons, we do not take their charges to
be the elementary charge
• You often see phrases—such as “the charge on a sphere,” “the
amount of charge transferred,” and “the charge carried by the
electron”—that suggest that charge is a substance
• You should, however, keep in mind what is intended: Particles
are the substance and charge happens to be one of their
properties, just as mass is
27. Charge is Quantized
• When a physical quantity such as charge can have only
discrete values rather than any value, we say that the quantity
is quantized
• It is possible, for example, to find a particle that has no
charge at all or a charge of -10e or -6e, but not a particle with
a charge of, say, 3.57e.
• The quantum of charge is small. In an ordinary 100 W
lightbulb, for example, about 1019 elementary charges enter
the bulb every second and just as many leave.
• However, the graininess of electricity does not show up in
such large-scale phenomena (the bulb does not flicker with
each electron), just as you cannot feel the individual
molecules of water with your hand.
29. Charge is Conserved
• If you rub a glass rod with silk, a positive charge appears on the
rod. Measurement shows that a negative charge of equal
magnitude appears on the silk
• This suggests that rubbing does not create charge but only
transfers it from one body to another, upsetting the electrical
neutrality of each body during the process
• This hypothesis of conservation of charge, first put forward by
Benjamin Franklin, has stood up under close examination, both
for large-scale charged bodies and for atoms, nuclei, and
elementary particles. No exceptions have ever been found. Thus,
we add electric charge to our list of quantities—including energy
and both linear and angular momentum—that obey a
conservation law.
30. Charge is Conserved
• Important examples of the conservation of charge occur in
the radioactive decay of nuclei, in which a nucleus
transforms into (becomes) a different type of nucleus. For
example, a uranium-238 nucleus (238U) transforms into a
thorium-234 nucleus (234Th) by emitting an alpha particle.
Because that particle has the same makeup as a helium-4
nucleus, it has the symbol 4He.
• The number used in the name of a nucleus and as a
superscript in the symbol for the nucleus is called the mass
number and is the total number of the protons and neutrons
in the nucleus. For example, the total number in 238U is
238. The number of protons in a nucleus is the atomic
number Z, which is listed for all the elements in Appendix F.
From that list we find that in the decay
238U :234Th _ 4He, (1)
31. Charge is Conserved
• The parent nucleus 238U contains 92 protons (a charge
of +92e), the daughter nucleus 234Th contains 90 protons
(a charge of +90e), and the emitted alpha particle 4He
contains 2 protons (a charge of +2e).We see that the
total charge is +92e before and after the decay; thus,
charge is conserved. (The total number of protons and
neutrons is also conserved:238 before the decay and
234+4=238 after the decay.)
• Another example of charge conservation occurs when
an electron e_ (charge-e) and its antiparticle, the
positron e+ (charge +e), undergo an annihilation
process, transforming into two gamma rays (high-
energy light):
32. Charge is Conserved
• In applying the conservation-of-charge principle, we must
add the charges algebraically, with due regard for their signs.
In the annihilation process of Eq. 2 then, the net charge of
the system is zero both before and after the event. Charge is
conserved.
• In pair production, the converse of annihilation, charge is
also conserved. In this process a gamma ray transforms into
an electron and a positron
33. Charge is Conserved
• The gamma ray, being electrically neutral, left no
trail. Still, you can tell exactly where it underwent
pair production—at the tip of the curved V, which
is where the trails of the electron and positron
begin
• Figure shows such a pair-production event that
occurred in a bubble chamber. A gamma ray
entered the chamber from the bottom and at one
point transformed into an electron and a positron.
Because those new particles were charged and
moving, each left a trail of tiny bubbles. (The trails
were curved because a magnetic field had been set
up in the chamber.)
34. Coulomb’s Law
• If two charged particles are brought near each other,
they each exert a force on the other. If the particles
have the same sign of charge, they repel each other.
That is, the force on each particle is directed away
from the other particle, and if the particles can
move, they move away from each other. If, instead,
the particles have opposite signs of charge, they
attract each other and, if free to move, they move
closer to each other.
35. Two charged particles repel
each other if they have the
same sign of
charge, either (a) both positive
or (b) both
negative. (c) They attract each
other if they
have opposite signs of charge
36. Coulomb’s Law
• This force of repulsion or attraction due to the
charge properties of objects is called an
electrostatic force. The equation giving the force
for charged particles is called Coulomb’s law
after Charles-Augustin de Coulomb, whose
experiments in 1785 led him to it. In terms of
the particles in, where particle 1 has charge q1
and particle 2 has charge q2, the force on
particle 1 is
37. Coulomb’s Law
• in which is a unit vector along an axis
extending through the two particles, r is the
distance between them, and k is a constant.
(As with other unit vectors, has a magnitude
of exactly 1 and no dimension or unit; its
purpose is to point.) If the particles have the
same signs of charge, the force on particle 1
is in the direction of ; if they have opposite
signs, the force is opposite
38. Coulomb’s Law
• Curiously, the form of is the same as that of
Newton’s equation for the gravitational force
between two particles with masses m1 and m2 that
are separated by a distance r :
in which G is the gravitational constant
39. Coulomb’s Law
• The constant k in by analogy with the gravitational
constant G, may be called the electrostatic constant.
• Both equations describe inverse square laws that
involve a property of the interacting particles—the
mass in one case and the charge in the other.
• The laws differ in that gravitational forces are
always attractive but electrostatic forces may be
either attractive or repulsive, depending on the signs
of the two charges. This difference arises from the
fact that, although there is only one kind of mass,
there are two kinds of charge
41. Coulomb’s Law
• The quantity ℇ0, called the
permittivity constant,
sometimes appears separately
in equations
• Still another parallel between
the gravitational force and the
electrostatic force is that both
obey the principle of
superposition. If we have n
charged particles, they interact
independently in pairs, and the
force on any one of them, let
us say particle 1, is given by
the vector sum
42. Useful Terms
• Electric Charge The strength of a particle’s electrical interaction with
objects around it depends on its electric charge, which can be either
positive or negative. Charges with the same sign repel each other, and
charges with opposite signs attract each other. An object with equal
amounts of the two kinds of charge is electrically neutral, whereas one
with an imbalance is electrically charged.
• Conductors are materials in which a significant number of charged
particles (electrons in metals) are free to move. The charged particles in
nonconductors, or insulators, are not free to move.
• The Coulomb and Ampere The SI unit of charge is the coulomb (C). It is
defined in terms of the unit of current, the ampere (A), as the charge
passing a particular point in 1 second when there is a current of 1
ampere at that point: 1 C (1 A)(1 s).
• This is based on the relation between current i and the rate dq/dt at
which charge passes a point: (electric current)
43. Useful Terms
• Coulomb’s Law: Coulomb’s law describes the electrostatic force between small (point)
electric charges q1 and q2 at rest (or nearly at rest) and separated by a distance r: (Coulomb’s
law)
• Here ℇ0=8.85 10-12 C2/N m2 is the permittivity constant, and 1/4ℼℇ0 = k = 8.99 * 109 Nm2/C2.
• The force of attraction or repulsion between point charges at rest acts along the line joining the
two charges. The net force on each charge is then found, using the superposition principle, as
the vector sum of the forces exerted on the charge by all the others.
• The two shell theorems for electrostatics are A shell of uniform charge attracts or repels a
charged particle that is outside the shell as if all the shell’s charge were concentrated at its
center.
• If a charged particle is located inside a shell of uniform charge, there is no net electrostatic
force on the particle from the shell.
• The Elementary Charge: Electric charge is quantized: any charge can be written as ne,
where n is a positive or negative integer and e is a constant of nature called the elementary
charge ( 1.602 *10-19 C). Electric charge is conserved: the net charge of any isolated system
cannot change.
44. Problem
• The nucleus in an iron atom has a radius of about
4.0 * 10-15 m and contains 26 protons.
• (a) What is the magnitude of the repulsive
electrostatic force between two of the protons that
are separated by 4.0 10-15 m?
• (b) What is the magnitude of the gravitational force
between those same two protons?
47. Problem
• Figure-a shows two positively charged particles fixed in place on an x
axis. The charges are q1=1.60*10-19 C and q2 = 3.20*10-19 C, and the
particle separation is R=0.0200 m. What are the magnitude and
direction of the electrostatic force on particle 1 from particle 2?
• Figure-c is identical to Figure-a except that particle 3 now lies on the x-
axis between particles 1 and 2. Particle 3 has charge q3=3.20 10-19 C
and is at a distance from particle 1. What is the net electrostatic force
on particle 1 due to particles 2 and 3?
• Figure-e is identical to Figure-a except that particle 4 is now included. It
has charge q4=3.20 10-19 C, is at a distance 3/4R from particle 1, and lies
on a line that makes an angle Ɵ = 60° with the x axis. What is the net
electrostatic force F1,net on particle 1 due to particles 2 and 4?
48. Figure
(a) Two charged particles of charges q1 and q2 are fixed in place on an x axis. (b) The free-
body diagram for particle 1, showing the electrostatic force on it from particle 2. (c) Particle
3 included. (d) Free-body diagram for particle 1. (e) Particle 4 included. (f ) Freebody diagram
for particle 1.
52. Problem
• Figure-a shows two particles fixed in place: a particle of charge q1= +8q
at the origin and a particle of charge q2=-2q at x=L. At what point (other
than infinitely far away) can a proton be placed so that it is in equilibrium
(the net force on it is zero)? Is that equilibrium stable or unstable? (That
is, if the proton is displaced, do the forces drive it back to the point of
equilibrium or drive it farther away?)
53. Figure
(a) Two particles of charges
q1 and q2 are fixed in
place on an x axis, with
separation L. (b)–(d) Three
possible locations
P, S, and R for a proton. At
each location, F1 is the force
on the proton from particle 1
and F2 is the force on the
proton from particle 2.
54. Solution
• If is the force on the proton due to charge q1 and is the force on the
proton due to charge q2, then the point we seek is where Thus,
This tells us that at the point we seek, the forces acting on the proton due to
the other two particles must be of equal magnitudes,
and that the forces must have opposite directions.
