Science Section 1 Academic Decathlon 25-26

William Gilbert (1544-1603)

Philosopher

Discovered "electric force" in 1600 by rubbing amber together

Amber

Elektron (In Greek)

Used in William Gilbert's experiment for the electric force

Old Western basic elements

Water, earth, fire, air

Fundamental elements cannot be made of anything because everything is made of it

Elements

From the Periodic Table

Made of smaller pieces

Atom

Atom = indivisible

All matter was made of atoms

Creates elements

Benjamin Franklin (1706-90)

Drafted Declaration of Independence

Kite & Thunderstorm experiment

Popular in France

Leyden Jar

Device that stores electricity and gives an electric shock

Inspired Ben Franklin's kit experiment

Electrical Fire

Benjamin Franklin

Attracted and repelled things

Electric charge in conserved

Actually electrically charged particles moving from atom to atom

Kite and thunderstorm experiment

Benjamin Franklin

Attached key to stand surrounded by small shelter

Measured static electricity buildup on key

Proved lightning was electrical

Particle

Fundamental piece of matter of which everything else is made

Nucleus

Center of atoms

Protons & neutrons

Protons

Positively charged

Similar mass to neutron

Made of quarks

Neutrons

Neutrally charged

Similar mass to proton

Made of quarks

Mass

Measured in kilograms

Determines object's response to forces

Like inertia

Kilograms

Measure of mass

1kg~1L Water

Avg person = 60-70kg

Inertia

Resistance to changes in motion

Like mass

Electron

Negatively charged

Surrounds nucleus

Equal number to protons, can be different

Electric Charge

Fundamental quality of a particle

Can be zero

Opposites attract, same repels

Newton's 1st Law of Motion

An object's inertia will allow it to keep going as long as there are no forces to stop it

Force

Interactions between objects

How one object can change the motion of another object

Measured in Newtons

1 Newton = Weight of 1 Apple

Newton's 2nd Law of Motion

Object feeling a force will accelerate in the direction of that force

More mass=more resistance

F=MA

Newton's 3rd Law of Motion

Every action has an equivalent reaction

Gravity of planets, attraction between protons/electrons

Quark

Makes up protons and neutrons

Positive Scientific Notion

10^1= 10

10^2= 100

10^3= 1000

Power = # Zeros After 1

Multiplying by 10

Negative Scientific Notion

10^-1= 0.1

10^-2= 0.01

10^-3= 0.001

Dividing by 10

Scientific Notation Conversions

1kg= 1,000 g = 1x10^3 g

1g= 1x10^-3 kg

1km= 1,000 m = 1x10^3 m

Fundamental Forces

Strong Nuclear Force & Weak Nuclear Force (Only occurs within nucleus)

Gravitational Force

Electromagnetic Force

Strong Nuclear Force

Keeps protons & neutrons within nucleus (otherwise they would repel or be unstabilized)

Only occurs within nucleus

Weak Nuclear Force

Transforms particles into other particles

Radioactive Decay

Only occurs within nucleus

Gravitational Force

Pulls mass towards other mass

Strength depends on masses & distance apart

FG=G(m1m2/r^2)

Electromagnetic Force

Attracts and repels charged particles

Keeps atoms together

Gravitational Force Equation

m= masses of 2 objects; r= distance between 2 objects; FG= Force of Gravity; G= Gravitational Constant (6.67x10^-11 N m^2/kg^2)

Inverse Square

Sensitive to changes in distance than mass

Only attractive

Inverse Square Law

Solves for a quantity that is inversely proportional to the distance squared

Jupiter, Sun, Earth

Jupiter is 5x further from the sun than Earth

Jupiter gets 1/25th the amount of light the Earth gets

Example of the Inverse Square Law

Gravitational Constant

aka Newton's Constant

Tells how strong a force you get

6.67x10^-11 N m^2/kg^2

Very small

Earth's Force

6x10^24

Mass of Proton

1x7x10^-27

Mass of an electron

9.1x10^-31

Coulomb's Law

q= Amount of charge on two objects; r= distance apart; k=constant (8.99x10^9 N m^2/C^2)

Electricity can attract and repel

Discovery of Coulomb's Law

Charles Coulomb, 1785

Torsion balance with a charged rod suspended by a string, twisted by electric forces from rod

Coulomb

Measurement of electric current

Very big compared to proton or electron (+-1.7x10^-19 coulombs)

Coulomb's Constant

k= 8.99x10^9 N m^2/C^2

Electric v. Gravitational Force

Electric force is much stronger (by more than 10^40)

Less noticeable because most atoms are electrically neutral, while everything has positive mass

Cloth & glass rod

Glass picks up a positive charge, cloth is negative charge due to stealing glass's electrons

Vector

Magnitude & Direction

EX Wind, Gravity

Scalar

Magnitude

EX Temperature

Simplified Gravitational Equation

FG=mg

m=mass; g= strength of gravitational field created by earth (depends on mass/distance of object, often 9.8 newtons/kg)

g decreases with square of distance

Satellite Gravity

g=90% of earth's

Moons gravity

g<1% of earth's

Simplified Electrical Force Equation

FE=qE

q=charge; E=electric field (newtons/coulomb), how much force a particle with charge q will feel at that location

Positive mass follows direction of gravity

Positive charge goes in the same direction as E, neg opposite

Positively charged object's electric field

Points away from object

Negatively charged object's electric field

Points towards object

Strength of proton's electric field

E=kq/r^2

Calculating a large object's electric field

Electric fields from multiple objects can be added together

2 Protons Electric field

Add together, looks like field w 2x strength of proton

In between (@ = magnitude) P1 points L, P2 points R, cancels out (0 force)

Proton/Electron Electric field

Very weak, looks like charge of zero

In between, proton points R, electron point R, reinforce

Around, points away from proton and towards Electron

Electric Dipole

Large, flat sheet with proton

Flat sheet is positively charged -> proton is pushed upwards & diagonal (cancelled out)

Gauss's Law

Find out what the electric field looks like for extended objects

Closed geometric shape, calculate the amount that passes through the "Gaussian Surface"

εo= Permittivity of free space; q=total charge within surface (=σA); φE= Electric Field Flux (=2EA)

Permittivity of Free Space (εo)

1/4(pi)k

Electric Field Flux (φE)

Scalar

φ=phi

Amount that passes through a given area

Depends on strength of electric field & orientation of relative to field

Normally E (strength of electric field) * A (surface area)

Large, flat sheet & cylinder

Top & Bottom of cylinder (same flux) :2 EA =q/εo

How much charge : 2 EA = σA/εo

Cancel out A: E = σ/2εo

σA

Charge Density

Van de Graff Generator

Vertical conveyor belt, continuously rubs two materials together at the bottom of a tower -> stray electrons gather at top, in a metal ball

Static Electricity

Two different materials rubbing against each other, one steals the others electrons and looks for a way out to prevent buildup

Electrically Polarized

When an object is neutral, but the positive nucleus is off to one side and the electrons are off to another

Electrons continue to be repelled, protons continue to be attracted

Ions

Uneven # of protons/electrons

Conductor

Quickly exchanges heat energy and charge with surroundings

Outer electrons are loosely bound to nucleus, allows them to freely jump

Metals (aluminum, copper)

Outer orbital shells are unfilled

Insulators

Do not allow electrons to move freely

Conductor that gains a net electric charge

Electrons are as far spread a part as they can be

Electric field = 0

(non zero=keep moving)

Faraday Cage

Sheilds the inside from electromagnetic radiation

Corners V Circles

Corners = more charge density of