electrostatics electrostatics - the study of electricity at rest

ELECTROSTATICS

• Electrostatics - the study of electricity at rest.

QuickTime™ and a decompressor

are needed to see this picture.

QuickTime™ and a decompressor

are needed to see this picture.

ELECTROSTATICS

Electrical Forces arise from particles in atoms-can be either repulsive or attractive

Like charges repel.

-protons repel protons ( + + )

-electrons repel electrons ( - - )

Unlike charges attract. -protons and electrons attract each other

(+ -)

ELECTROSTATICS

QuickTime™ and a decompressor

are needed to see this picture.

ELECTROSTATICSCharge – a property that is attributed with

attractive or repulsive behaviorIn the atom, by convention (general agreement),

electrons are assigned a negative charge (-)

protons are assigned a positive charge (+), and

neutrons are neutral (0).

QuickTime™ and a decompressor

are needed to see this picture.

ELECTROSTATICSFacts about Atoms:

-positively charged nucleus surrounded by negatively charged electrons

-electrons are identical (same mass and same amount of negative charge)

-nucleus is made of positively charged protons and neutral neutrons

-all protons are identical (same mass and same amount of positive charge)

-all neutrons are identical (same mass)

ELECTROSTATICSAtoms have the same number of protons and electrons.

# of protons = # of electronsNeutral atom has a net charge of zero.

Atom with extra electrons has a net negative charge.

negative ion

Atom with less electrons has a net positive charge.

positive ion

Only electrons can be lost or gained - not protons or neutrons.

Atoms and Ions

UNIT OF CHARGE

Coulomb - SI unit of charge

- abbreviated C

1 Coulomb is the charge on

6.24 x 1018 electrons

The charge on 1 electron is

(1/6.24 x 1018) = -1.6 x 10-19 C

COULOMB’S LAWThe electrical force between charged particles is directly related to the charge of each particle and

inversely related to the square of the distance between the particles.

F = k q1q2

----------

d2

k = 9.0 x 109 N.m2

C2

COMPARE and CONTRAST

NEWTON’S LAW OF GRAVITATIONF = G m1m2 G = 6.7 x 10-11 N.m2

d2 kg2

COULOMB’S LAWF = k q1q2 k = 9.0 x 109 N.m2

d2 C2

COMPARE and CONTRAST

Newton’s Coulomb’s

Gravitation Electrical

Similarities

1. 1.

2. 2.

Differences1. 1.

2. 2.

COMPARE and CONTRAST

Newton’s Coulomb’s

Gravitation Electrical

Similarities

1. Product of masses 1. Product of charges

2. Inverse square law 2. Inverse square law

Differences1. Very small constant 1. Very large constant

(very small force) (very large force)

2. Attractive force only 2. Attractive and repulsive

INSULATORS and CONDUCTORS

Conductors - materials that allow electric charge to move easily - “loose” electrons

Examples:

Insulators - materials that do not allow electric charge to move easily

Examples:

CHARGING MATERIALS

• FRICTION - this is the process of adding or taking away electrons by moving objects across each other.

QuickTime™ and a decompressor

are needed to see this picture.

CHARGING MATERIALS

• CONDUCTION OR CONTACT - the process of giving a charge to an object by touching it with another charged object.

QuickTime™ and a decompressor

are needed to see this picture.

CHARGING MATERIALS

• INDUCTION - the process of charging an object by bringing another charged object near but not touching the object.

QuickTime™ and a decompressor

are needed to see this picture.

CHARGE POLARIZATION

• An object can be electrically

polarized when one side of

the object is more negative

(or positive) than the other

side of the object.

QuickTime™ and a decompressor

are needed to see this picture.