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Discovering the matters and the laws
of the universe
Key Words
Universe, Energy, Quantum mechanics,
Chemical reaction, Structure of matter
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Quiz
Quiz 1 n  A measure of the ability of a material to absorb heat is referred
as its
1. thermal energy
2. heat capacity
3. heat transfer
4. temperature Quiz 1 n  A measure of the ability of a material to absorb heat is referred
as its
1. thermal energy
2. heat capacity
3. heat transfer
4. temperature Quiz 2
n  Which of the following statements is not consistent with the
second law of thermodynamics?
1. All isolated systems will tend to remain ordered indefinitely
2. Heat will not flow spontaneously from a cold body to a hot
body
3. No engine is one hundred percent efficient in converting
energy to work
4. The evolution of more complicated forms of life on Earth
does not annul the second law Quiz 2
n  Which of the following statements is not consistent with the
second law of thermodynamics?
1. All isolated systems will tend to remain ordered indefinitely
2. Heat will not flow spontaneously from a cold body to a hot
body
3. No engine is one hundred percent efficient in converting
energy to work
4. The evolution of more complicated forms of life on Earth
does not annul the second law Quiz 3
n  A device that converts stored energy into the kinetic energy of
electrons passing through an outside wire is called a(n)
1. battery
2. compass
3. electromagnet
4. motor
Quiz 3
n  A device that converts stored energy into the kinetic energy of
electrons passing through an outside wire is called a(n)
1. battery
2. compass
3. electromagnet
4. motor
November 14, 2016
Electricity and Magnetism
What is lightning?
Electrical charge, electricity, static electricity;
Electrical field, Coulomb’s law
Magnet, magnetic force, magnetic field;
Battery, AC, DC, electric motor
Contents
n  Introduction
n  Electricity, and Magnetism
n  Electromagnetism
Introduction
- Static electricity
- Movements of electrons
1. Introduction
Newton’s laws of motion tell us that nothing happens
without a force.
We have learned the law of gravity.
1. Introduction
Newton’s laws of motion tell us that nothing happens
without a force.
We have learned the law of gravity.
However,
Does gravity force explain how your hair tends to stand
on end, or how does a compass needle swing around to
the north?
1. Introduction
Newton’s laws of motion tell us that nothing happens
without a force.
We have learned the law of gravity.
However,
Does gravity force explain how your hair tends to stand
on end, or how does a compass needle swing around to
the north?
àThese phenomena occur by a different type of forces
in nature from Gravitational force
1. Introduction
Newton’s laws of motion tell us that nothing happens
without a force.
We have learned the law of gravity.
However,
Does gravity force explain how your hair tends to stand
on end, or how does a compass needle swing around to
the north?
àThese phenomena occur by a different type of forces
in nature from Gravitational force
è Electrical or magnetic forces:
1. Introduction
Newton’s laws of motion tell us that nothing happens
without a force.
We have learned the law of gravity.
However,
Does gravity force explain how your hair tends to stand
on end, or how does a compass needle swing around to
the north?
àThese phenomena occur by a different type of forces
in nature from Gravitational force
è Electrical or magnetic forces:
Electromagnetic force!
Introduction
Static Electricity
Observations
Rub a balloon filled with air on your hair. Then hold it up to a wall.
The balloon will stay there by itself.
Now rub two balloons on your hair, hold them by strings at the end
and put them next to each other. They'll move apart.
Introduction
Static Electricity
Observations
Rub a balloon filled with air on your hair. Then hold it up to a wall.
The balloon will stay there by itself.
Now rub two balloons on your hair, hold them by strings at the end
and put them next to each other. They'll move apart.
Introduction
Static Electricity
Observations
Rub a balloon filled with air on your hair. Then hold it up to a wall.
The balloon will stay there by itself.
Charged
Charged
Now rub two balloons on your hair, hold them by strings at the end
and put them next to each other. They'll move apart.
Charged
Charged
Introduction
Static Electricity
Observations
Rub a balloon filled with air on your hair. Then hold it up to a wall.
The balloon will stay there by itself.
Attractive Force
Charged
Charged
Now rub two balloons on your hair, hold them by strings at the end
and put them next to each other. They'll move apart.
Charged
Repulsive Force
Charged
Introduction
Static Electricity
Observations
Rub a balloon filled with air on your hair. Then hold it up to a wall.
The balloon will stay there by itself.
Attractive Force
Charged
Charged
Now rub two balloons on your hair, hold them by strings at the end
and put them next to each other. They'll move apart.
Charged
Repulsive Force
Charged
Introduction
Static Electricity (cont’d)
n  Electrical charge:
The objects in the given situation demonstrated in
previous slide, are called “charged”, and they possess
electrical charge.
n  Electricity:
The force that moves such charged objects toward and
away from each other is electricity (named after the
Greek word for amber)
n  Static electricity:
The electrical charge doesn’t move once it has been
placed. The force is called “static” electricity.
Introduction
Movement of electrons 1 n  There are two kinds of electrical charge: + and –
n  All objects are made of fundamental building blocks
called atoms, and all atoms are made up of smaller
particles that have electrical charge.
Neutral atom
Introduction
n  Any object, Atoms, Building blocks of atoms
Any
object
Nucleus : +
protons (positive)
+ neutrons (neutral)
Electron: - (negative)
Atom:
nucleus + electrons
(+)
(-)
Introduction
n  Most atoms are electrically neutral
è positive charge of nucleus cancels negative charge
of electrons:
number of (+) charges = number of (-) charges
Example:
Introduction
n  Electrons are loosely bound to atoms
In metal, electorons can move freely or can react with
other elements.
nucleus
Nucleons
tightly bound
within the
nucleus
electron
Loosely bound to the
atom
à can be stripped off
à can be added to
Introduction
Movement of electrons 2 * When electrons are stripped off of a material,
( # of (+) charges > # of (-) charges)
the object has a net excess of positive charge
è the object acquired a positive electrical charge
* When extra electrons are added to it
( # of (+) charges < # of (-) charges)
è the object acquired a negative electrical charge
*
+
__
Attractive Force
+
+
Repulsive Force
Electricity, and Magnetism
- Electricity
- Magnetism
- Electric circuits
Electricity
Coulomb’s law
Charles Augustin de Coulomb (1736-1806), a French
physicist, after a series of experiments, discovered that
electrical force is very similar to the gravitational
force.
Coulomb’s law
n  The force between any two electrically charged objects
is proportional to the product of their charges divided
by the square of the distance between them.
Electricity
Coulomb’s law (cont’d)
Coulomb’s law
Force (newtons) = k x 1st charge x 2nd charge
distance2
F = k x (q1 x q2)
d2
Distance d in meters, charge q in unit of electrical charge called
coulomb (C), and
k is the coulomb constant (9.00 X 109 newton-meter2/coulomb2).
We define 1 C as the charge on 6.24 X 1018 electrons.
Electricity
Electric field
Imagine that an electrical charge is sitting at a point.
Electricity
Electric field
Imagine that an electrical charge is sitting at a point.
If you brought a second charged object to a spot near the
first,
Electricity
Electric field
Imagine that an electrical charge is sitting at a point.
If you brought a second charged object to a spot near the
first, the second object would feel a force.
Electricity
Electric field
Imagine that an electrical charge is sitting at a point.
If you brought a second charged object to a spot near the
first, the second object would feel a force.
Electrical field:
Every charged object exerts forces on its surroundings to
create an electric field. Electricity
Electric field (cont’d)
An electric force is represented by an electric field,
with arrows that represent the direction and strength of
the field at every point.
Magnetism
Magnetism
Just as electrical phenomena,
we find another type of interesting phenomena in our
nature, so called magnetism.
Observations
Ancient people learned about “magnetism” from naturally
magnetized pieces of iron ore, which attract pieces of iron.
The word magnet in Greek meant "stone from Magnesia”,
a part of ancient Greece.
Magnetism
Magnetism
Just as electrical phenomena,
we find another type of interesting phenomena in our
nature, so called magnetism.
Observations
Ancient people learned about “magnetism” from naturally
magnetized pieces of iron ore, which attract pieces of
iron. The word magnet in Greek meant "stone from
Magnesia”, a part of ancient Greece.
Magnetism
Terms
n  Magnet: a piece of iron that attracts objects made of iron
towards it
n  Magnetic force: a force described by magnetism
n  Magnetic Poles:
Each end of a magnet is called a pole.
One end points north and the other points south.
The compass is the first magnetic device on record.
1. Every magnet has two poles
2. Like magnetic poles repel each other, while unlike
poles attract
Magnetism
Magnetic poles 1
Every magnet has two poles (di-poles)
S
N
Magnetism
Magnetic poles 1
S
S – monopole???
N
N – monopole???
Magnetism
Magnetic poles 1
Why Magnetic monopoles don’t exist???
S
S – monopole???
N
N – monopole???
Magnetism
Magnetic poles 2
n  Earth is a giant magnet!
One end of a compass points to one of its pole in the
north, the other points to the south.
Magnetism
Magnetic field 1
n  Magnetic field: magnets display a curving field pattern
n  A magnetic force is represented in terms of a
magnetic field, with arrows that indicate the direction
and strength of magnetic forces at any point around
the magnet
Magnetism
Magnetic field 1
n  Magnetic field: magnets display a curving field pattern
Iron filings show the pattern of magnetic field
Magnetism
Magnetic field 1
Iron filings show the pattern of magnetic field
Magnetism
Magnetic field 2
n  Earth’s magnetic field
Magnetism
Polar lights n  Aurora
is caused by particles from the Sun interacting with
Earth’s magnetic field Magnetism
No magnetic monopole Pairs of Poles
n  All magnets found in nature have both north and south
poles
“There are no isolated magnetic poles in nature”
Or equivalently,
“There is no magnetic monopole in nature”
Why Magnetic monopoles don’t exist ?
è Connection between electricity and magnetism!
Magnetism
No magnetic monopole Pairs of Poles
n  All magnets found in nature have both north and south
poles
“There are no isolated magnetic poles in nature”
Or equivalently,
“There is no magnetic monopole in nature”
Why Magnetic monopoles don’t exist ?
è Connection between electricity and magnetism!
Let’s see the connection in the next section. Electromagnetism!
Electric circuit
Electric Circuit
Most of our contact with electricity comes from moving
charges, not static electricity
n  Electrical current: a flow of charged particles
n  Battery: an electrochemical cells that convert stored
chemical energy into electrical energy
Electric circuit
Electric circuits 1 n  Electric circuit:
An unbroken path of material, called electrical conductors,
that carries electricity (Ex. Copper wire).
Closed path
Energy
source
Device
Every circuit consists of three parts: a source of energy
(ex. battery), a closed path made of metal wire, and a
device such as a motor or a light bulb.
Electric circuit
Electric circuits 1 n  Electric circuit (cont’d):
* The unit of the amount of electrical current that flows in
a wire: ampere (amp)
1 amp of current = 1 coulomb of charge per second
Electric circuit
Electric circuits 1 n  Electric circuit (cont’d):
* Analogy between the current of water and electrical
current
electrical current passing through a circuit : water current
flowing through a pipe
voltage, pressure, by energy source in circuit : water pressure
in plumbing system
wires through electrons flow : pipes carrying water
è Resistance of current depends on materials of wires
Electric circuit
Electric resistance
n  Electrical resistance is measured in a unit called ohm
è Higher the resistance, the more electric energy is
converted into heat
Ohm’s law:
voltage (volts) = current (amps) X resistance (ohms)
V=IxR
Electric circuit
Power of electric appliance
n  Power consumed by an electric appliance is equal to
the product of the current and the voltage
power (watts) = current (amps) X voltage (volts)
P=IxV
n  Two kind of electric circuits
* series circuit: all loads linked along a single loop
(Ex. Christmas lights)
* parallel circuit: different loads are situated on
different wire loops
Electric circuit
Lightning
_ __
+++
Electric circuit
Lightning
Lightning stroke is the electrical current between
cloud and ground when collisions of particles in the clouds
produce a negative charge at the bottom of the cloud and a
corresponding build of positive charge in objects on the
ground.
_ __
+++
Electromagnetism
- Connection between electricity and magnetism
- Electric effects from magnetism
- Magnetic effects from electricity
Electromagnetism
Connections between Electricity and Magnetism Electricity and Magnetism seem as different from
each other, but in fact they are intimately related to
each other!
Electromagnetism
Magnetic effect from electricity 1
n  Magnetic effect from electricity
Whenever an electrical current flows through a wire
a magnetic field appears around that wire
Electromagnetism
Magnetic effect from electricity 1
n  Magnetic effect from electricity
Electrical current
Electromagnetism
Magnetic effect from electricity 1
n  Magnetic effect from electricity
Induced
magnetic
field
Electrical current
Electromagnetism
Magnetic effect from electricity 1
n  Magnetic effect from electricity
Ampere’s law
Induced
magnetic
field
Electrical current
Electromagnetism
Magnetic effect from electricity 1
n  Magnetic effect from electricity
Whenever an electrical current flows through a wire
à in an experiment, battery was connected to generate
an electrical current
a magnetic field appears around that wire
à in the experiment, a compass needle on a nearby
table moved
Electromagnetism
Magnetic effect from electricity 2
n  Electromagnet:
We can create a magnetized piece of iron simply by
running electrical current around a loop of wire
èThe stronger the current, the stronger the magnetic
field will be
Electromagnetism
Magnetic effect from electricity 2
n  Electromagnets:
Ex) Electric motor:
A pair of permanent magnets and a rotating loop of wire
inside the poles of the magnets
When the induced
magnetic field faces the
same pole (N-N and S-S)
as the permanent
magnet’s, the motor
rotates.
Electromagnetism
Magnetic effect from electricity 2
n  Electromagnets:
Ex) Electric motor: Electrical energy à Machinery energy
A pair of permanent magnets and a rotating loop of wire
inside the poles of the magnets
When the induced
magnetic field faces the
same pole (N-N and S-S)
as the permanent
magnet’s, the motor
rotates.
Electromagnetism
Question:
Why magnetic monopoles don’t exist?
Electromagnetism
Question:
Why magnetic monopoles don’t exist?
Magnetism in nature is ultimately related to the
arrangement of electrical charges rather than to
anything to matter itself.
Electromagnetism
Electrical effects from magnetism 1
n  Electrical effects from magnetism
Michael Faraday (1791-1867) discovered that
“Electrical fields and electrical currents can be produced
by changing magnetic fields”.
Electromagnetism
Electrical effects from magnetism 1
n  Electrical effects from magnetism (cont’d)
Exp. setup
Faraday placed two electromagnets – two coils of wire-,
then he watched that
when an electrical current flowed through one of the coils
of wire
è a strong electrical current developed in the second coil
of wire even though it was not connected to a battery
Electromagnetism
Electrical effects from magnetism 1
n  Electrical effects from magnetism (cont’d)
Exp. setup
Faraday placed two electromagnets – two coils of wire-,
then he watched that
when an electrical current flowed through one of the coils
of wire (è when magnetic field appear)
è a strong electrical current developed in the second coil
of wire even though it was not connected to a battery
Electromagnetism
Electrical effects from magnetism 1
n  Electrical effects from magnetism
“Electrical fields and electrical currents can be produced
by changing magnetic fields”.
Induced
magnetic field
battery
Two coils
Galvanometer:
read induced
electric current
at the moment
when the switch
is on
Electromagnetism
Electrical effects from magnetism 2
n  Electrical effects from magnetism
Ex) Electric generators:
Electrical currents are produced by rotating coils
between two poles of permanent magnets, in other
words, by changing magnetic fields
AC(alternating current): direction keeps alternating
Ex) Home appliances
DC (Direct current): in only one direction
Ex) Produced by batteries
Electromagnetism
Electrical effects from magnetism 2
n  Electrical effects from magnetism
Ex) Electric generators:
AC generator
DC generator
Electromagnetism
Electrical effects from magnetism 2
n  Electrical effects from magnetism
Ex) Electric generators: Machinery energy àElectrical energy
AC generator
DC generator
Electromagnetism
Maxwell’s equations
Electromagnetic force – A fundamental force in nature
n  Maxwell’s equations:
Four fundamental laws of electricity and magnetism
1. Coulomb’s law: like charges repel, unlike attract
2. There are no magnetic monopoles in nature
3. Magnetic phenomena can be produced by electrical
effects
4. Electrical phenomena can be produced by magnetic
effects Next topic is,
Waves and electromagnetic radiation
: Chapter 3
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