Properties of Objects
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Properties of Objects. Fundamental Particles. Atoms and Ions. Quantization of Charge. Conservation of Charge. Conductors, Insulators and Semiconductors. Polarization. How to Put Charge on an Object. Physical Properties That which is proper to anything; a peculiar quality of a thing;

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Properties of Objects

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Properties of objects

Properties of Objects

Fundamental Particles

Atoms and Ions

Quantization of Charge

Conservation of Charge

Conductors, Insulators and Semiconductors

Polarization

How to Put Charge on an Object


Properties of objects

Physical Properties

That which is proper to anything;

a peculiar quality of a thing;

that which is inherent in a subject, or naturally essential to it;

an attribute;

as, sweetness is a property of sugar.

Physical properties, or those which result from the relations of bodies to the physical agents,

light, heat, electricity, gravitation, cohesion, adhesion, etc.,

and which are exhibited without a change in the composition or kind of matter acted on.

http://www.wordiq.com/dictionary/Properties

Examples of physical properties of objects include…

Color

Mass

Hardness


Properties of objects

Intrinsic Physical Properties

An intrinsic physical property is a property of a set of objects that is constant throughout the entire set over space and time.

Examples of intrinsic physical properties of an NFL football include…

shape

material

weight

color

size

texture


Properties of objects

Intrinsic Physical Properties of Fundamental Particles

Everything in the universe is made up of a finite number of fundamental particles.

Each of these particles has the following intrinsic physical properties.

mass

size

charge

spin


Properties of objects

There are only two types of charge called positive and negative

Unlike charges attract

and like charges repel.


Properties of objects

Why positive and negative?

Imagine what it would be like for the types of charges to be named in a different way.

Which of these would best lead to an understanding of the difference between these types of charge and why?

A and B

Good and Evil

Left and Right

Jack and Jill


Properties of objects

The universe is made of 28 fundamental particles

6 quarks, 6 leptons, their antiparticles and some force particles.

All figures shown here are from Lawrence Berkley National Laboratory

“The Particle Adventure”


Properties of objects

Most charge that we experience is found in the quarks and the electron.

The fundamental unit of charge is

All figures shown here are from Lawrence Berkley National Laboratory

“The Particle Adventure”

Each quark carries a fraction of this charge.

Electrons have a charge of -e


Properties of objects

Fundamental Charge

Quarks are only typically in combinations of three called protons and neutrons

A proton contains 1 down and 2 up quarks (+echarge)

A neutron contains 1 up and 2 down quarks (0 charge)

An electron is a fundamental particle (-e charge)

All figures shown here are from Lawrence Berkley National Laboratory

“The Particle Adventure”


Properties of objects

Charge found on most objects comes typically from one place…

The object has either too many or too few electrons.

Positivechargeis created when an atomloses an electron.

This is called a positive ion.

Negative chargeis created when an atomgains an electron.

This is called a negative ion.


Properties of objects

All ordinary matter consists of …

ProtonsMass = 1.67x10-27 kgCharge = +e

NeutronsMass = 1.67x10-27 kgCharge = 0

ElectronsMass = 9.11x10-31 kgCharge = -e

All ordinary matter must therefore have

a total charge which is an integer

multiple of e.

Charge is designated by either

Q or q.


Properties of objects

Example 1

Dr. Mike puts electrons on a neutral balloon by rubbing it in his hair. The balloon gains -6.3 μC of charge. How many excess electrons did the balloon receive from Dr. Mike?

Answer

The number is given by Nelectrons in the equation from the previous slide.


Properties of objects

Example 2

Dr. Mike puts electrons on a neutral balloon by rubbing it in his hair. The balloon gains -6.30 μC of charge. By how much did Dr. Mike’s weight change?

Answer

In Example 1, we calculated that the balloon received 3.93 x 1013 electrons. The weight of these additional electrons is then found as follows.


Properties of objects

Example 3

Dr. Mike puts electrons on a neutral balloon by rubbing it in his hair. His hair loses 3.5 x 1016 electrons. How much charge does Dr. Mike have when he is finished?

Answer

The charge is given by Q in the equation from the previous slide.


Properties of objects

Conservation

The amount of charge in the universe never changes.

Example

Dr. Mike puts electrons on a balloon by rubbing it in his hair. The balloon gains -6.3 μC of charge. How much charge does Dr. Mike’s hair have after he has done this?

Answer

The electrons moved from Dr. Mike to the balloon. Thus, the charge that move to the balloon was taken away from Dr. Mike and he has +6.3 μC of charge more than he had when he began.

The total charge in the universe is still the same as it was when he began.


Properties of objects

You can easily determine the number of electron and protons in a mole of some element.

Example

How much negative electron charge is in 3 moles of oxygen?

Answer

There are Avogadro’s number of oxygen atoms in one mole. Using the periodic table (look it up on the web or in your chemistry textbook), we see that there are 8 electrons in on oxygen atom. And there is –e charge in each electron. So we have…

Note: There are just as many protons. So 3 moles of oxygen is actually neutral.


Properties of objects

In an insulator, all of the electrons are bound to a nucleus…

even the excess charges which stay right where they were forced to be by friction.


Properties of objects

In a conductor, some of the electrons are free to move between atoms.

Excess electrons will move freely as well, but they will stay on the surface of the conductor.


Properties of objects

In a semiconductor, the electrons cannot move unless given a high enough energy.

They are insulators when the energy is low.

and conductors when the energy is high


Properties of objects

A photoconductor is a semiconductor that uses light as its input energy.

They are insulators when the light energy is low.

and conductors when the light energy is high


Properties of objects

L

Dipoles

Dipoles are pairs of equal positive and negative charge that can rotate but not translate.

The intrinsic physical properties of the dipole are its charge and its length. (It also has mass and spin but we will almost never speak of the mass or spin of a dipole.)

The dipole is sometimes described by its dipole moment. The magnitude of the dipole moment is given by the equation

and it points from positive to negative in direction.

-q

+q


Properties of objects

Polarization

Dipoles always attract charged objects.

  • A negatively charged object causes the dipole to rotate so that the positive charge is closer to the conductor.

  • A positively charged object causes the dipole to rotate so that the negative charge is closer to the conductor.


Properties of objects

Inductors and conductors sometimes exchange charge by rubbing them together.

Use the Tribolectric Table to know which way the charges move.


Properties of objects

In conductors, electrons are free to move…

There are two ways to add charge to a conductor.

  • Touching a charged rod to a conducting sphere transfers electrons to the sphere.

    This is called charging by contact.

What would happen if the rod were positive to begin with?

A negative total charge remains


Properties of objects

In conductors, electrons are free to move…

There are two ways to add charge to a conductor.

  • If a charged rod is simply brought near a conducting sphere, the electrons will begin to move. And, some will go into the ground.

    This is called charging by induction.

What would happen if the rod were positive to begin with?

A positive total charge remains


Properties of objects

In insulators, electrons are not free to move. They stick to the atom…

Insulators can shift their charges and will therefore attract any charged conductor.

  • A negative conductor repels the electrons and is then attracted by the closer protons.

  • A positive conductor attracts the electrons and is then attracted by these closer electrons.


Properties of objects

Dipoles are pairs of positive and negative charge that can rotate but not translate.

Like insulators they always attract the conductor.

  • A negative conductor causes the dipole to rotate so that the positive charge is closer to the conductor.

  • A positive conductor causes the dipole to rotate so that the negative charge is closer to the conductor.


Properties of objects

Properties of Objects

Fundamental Particles

Atoms and Ions

Quantization of Charge

Conservation of Charge

Conductors, Insulators and Semiconductors

Polarization

How to Put Charge on an Object


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