Electrostatics

The study of electric charges

The Three Subatomic Particles – A Review

Proton – Positive Charge (+), p+

Neutron – No Charge (0), n0

Electron – Negative Change (-), e-

In physics, “charge” is represented by the letter “q”

Electric Charges on Objects A charged object has an unequal

balance of positive and negative charges

Objects can be charged two ways… Positive (+), such as vinyl and rubber Negative (-), such as fur, glass, and

wool

How to Make a Charged Object(or, How to Transfer Charge)

Friction or Contact Rubbing two objects together, or even just

touching them, causes elctrons to move from the atoms of one object to the atoms of another object

Scuffing socks on the floor, rubbing a balloon on your hear, Swiffer dusters

Induction Electrons “jump” from one object to another

when they are brought in close contact, but do not touch

Using a charged balloon to raise the hairs on your arm, Van de Graaff generator

Properties of Charged Objects

Like charges repel, unlike (opposite) charges attract

Charges are not created, or destroyed – they are separated or combined (moved) Electrons added to, or removed from,

atoms Charges exert a force on other

charges over a distance

Because there’s a force, there are vectors

Electric force vectors show the Electric Field

ALWAYS point from (+) to (-) charges

For a single charge…

+ -

POSITIVE CHARGE NEGATIVE CHARGE

For Two Charges…

Equal but opposite charges

Two like charges (positive or negative)

Magnets -Magnets have North and South poles

-If you break a magnet the broken pieces will still have North and South Poles

- Magnets produce magnetic fields that look similar to electrical fields

Conductors & Insulators Conductors allow charge to move easily

through them Metals

Insulators DO NOT allow charge to move easily through them Wood, Styrofoam

Materials usually exhibit the same property for heat transfer

The Unit of Charge Called a Coulomb (C) 1 Coulomb (C) has a charge equal to

6.25 x 1018 electrons Charge of 1 electron = -1.6 x 10-19 C

Units of Charge The coulomb is actually a very large

unit for static electricity. We need to use the metric prefixes

and scientific notation: 1 μC = 1 x 10-6 C (μ = “micro”) 1 nC = 1 x 10-9 C (n = “nano”) 1 pC = 1 x 10-12 C (p = “pico”)

Calculating Charge - Example

If 16 million electrons are removed from a neutral sphere, what is the charge on the sphere in coulombs?

ANSWER: 2.56 x 10-12 C