Science

meaning of elektron in Greek

amber

“electrical fire” definition

electrically charged particles moving between atoms

nucleus definition

center of every atom

proton, electron, neutron definitions

positively particles, non-charged particles, negatively charged particles (respectively)

Newton’s 3 Laws of Motion

1. An object at rest remains at rest, an object in motion remains in motion (unless there is an unbalanced force).

2. An object’s acceleration is directly proportional to the force applied on it (F=ma).

3. Every action (force) has an equal and opposite reaction (force).

mass of proton

1.7\times10^{-27} \text{ kg}

mass of electron

9.1\times10^{-31} \text{ kg}

What are the four fundamental forces?

1. electromagnetic force

2. strong nuclear force

3. weak nuclear force

4. gravitational force

strong nuclear force definition (as per Curriculum)

keeps protons within nucleus (strongest force, acts over short distances)

weak nuclear force definition (as per Curriculum)

transforms particles into other particles, i.e. radioactive decay

equation for gravitational force ANYWHERE

F_G=

F_G=G\frac{m_1m_2}{r^2}

Coulomb's Law

F_E=\frac{kq_1q_2}{r²}

charge of proton/electron

\pm1.7\times10^{-19} \text{ coulombs}

k (Coulomb's constant)

8.99\times10^9 \frac{Nm²}{C²}

scalar fields vs. vector fields + examples from Curriculum

scalar fields: no direction, just magnitude (ex. temperature in room)

vector fields: direction and magnitude (ex. wind over Earth’s surface)

equation for gravitational force close to Earth

F_G=

F_G=mg

m is mass of object experiencing F_G, g is gravitational field created by Earth

strength of Earth’s gravitational force near surface

g

g=9.8 \text{ N/kg}

equation for vector field of electric force

F_E

F_{E}=qE , E is electric field in Newtons/Coulombs

equation for electric field

E

E = \frac{kq}{r²}

Gauss' law

\Phi_E=\frac{q}{\epsilon_0}

symbol for permittivity of free space

\epsilon_0

equation for permittivity of free space

\epsilon _ 0

\epsilon_0=\frac{1}{4\pi k}

symbol for electric field flux

\phi_{E}

equation for electric field flux

\Phi_{E}=

\Phi _E = EA

E is the strength of the constant electric field, A is the area of the Gaussian surface

symbol for charge density

\sigma

insulators vs. conductors

insulators: materials that don’t allow electrons to move freely

conductors: outer electrons are loosely bonded to nucleus, can easily move between atoms

What is the electric field inside a charged conductor?

0 (imagine room w/ people wanting to be as far away from each other as possible, w/ one person in the center)

3 Laws of Thermodynamics

1. Conservation of energy: energy cannot be created or destroyed, only transferred.

2. Heat flows from high temperature objects to low temperature objects.

3. No substance can ever reach a temperature of absolute zero.

“phlogiston” definition

it was originally thought that heat was its own substance called phlogiston

heat definition (as per Curriculum)

energy moving between objects at different temperatures

kinetic energy definition

the type of energy an object has due to its motion

temperature definition

average kinetic energy of atoms of a substance

gravitational potential energy definition

the type of energy an object has due to its position in a gravitational field

electric potential energy definition

the type of energy an object has due to its position in a electric field

voltage definition

differences in electric potential

electric potential definition

electric potential energy divided by charge

change in electric potential energy equation

\Delta E =

\Delta E = qV

What analogy is used in the Curriculum to explain how a proton moves from a positively charged metal plate towards a negatively charged metal plate?

a ball rolling downhill from high potential to low potential

battery definition

device that maintains constant voltage by keeping 2 collections of positive & negative charge separate from each other

electric current definition

amount of charge that flows past a point per second

Ohm's law

I=\frac{V}{R}

I is current, V is voltage of battery, R is resistance

resistance of series circuit:

R_{series}=

add together resistances of each resistor:
R_{series} = R_1 + R_2 + … + R_n

resistance of parallel circuit:

R_{parallel}

reciprocal of total resistance is sum of reciprocal of each resistor:\frac{1}{R_{parallel}} = \frac{1}{R_1} + \frac{1}{R_2} + … + \frac{1}{R_n}

power in terms of current and voltage

P = IV

capacitor definition

two conductors separated by small distance

capacitor example from Curriculum

Leyden jar

capacitance definition

how much charge a capacitor can store

dielectric definition

material placed between two conductors in capacitor

purpose of dielectrics

to prevent dielectric breakdown and toallow capacitors to hold more charge at lower voltages

ferromagnetic definition

permanent magnet

paramagnetic definition

impermanent magnet; only magnetized when exposed to external magnetic field

right-hand rule for magnetic field

right-hand rule for magnetic force

magnetic force equation

\vec{F}=q\vec{v}\vec{B}

where \vec{B} is magnetic field and \vec{v} is velocity of particle

strength of Earth's magnetic field

25\text{-}65 \text{ microTeslas}

use of mass spectrometer

determine atomic composition of unknown sample

Who discovered the electron and when?

J.J. Thomson in 1897

purpose of Ampere's law (as stated by Curriculum)

determine what magnetic field around objects looks like

equation of magnetic field of Amperian loop

B=

B=\frac{\mu_0I}{2\pi r} or B(2\pi r)=\mu_0I

B is magnetic field, I is current passing through Amperian loop, 2\pi r is the length around Amperian loop

symbol for permeability of free space

\mu_0

solenoid definition

multiple circular loops of wires

equation for magnetic field of solenoid

B=\mu_0I(\frac{N}{L})

Faraday's law

V=-N\frac{\Delta\Phi_{B}}{\Delta t}

alternating current (AC) definition

current (and magnetic field) is constantly switching directions

diode definition

device that allows current to flow through it in only one direction

inductor definition

solenoid attached to circuit at either end

purpose of inductor

to resist changes in current in electric circuit

What happens when you have both a capacitor and an inductor?

capacitor discharges, inductor opposes decrease in current using a countercurrent, capacitor recharges, and so on (think a swinging pendulum)

frequency of capacitor + inductor system

f=\frac{1}{2\pi\sqrt{LC}}

L is inductance of inductor, C is capacitance of capacitor

Who created the first electric light and when?

Frank Hauksbee in 1705 ("barometric light")

How did Humphrey Davy's arc lamp work?

dielectric breakdown between two pieces of metal created a miniature lightning bolt

velocity of electromagnetic wave using permittivity & permeability of free space

v=\frac{1}{\sqrt{\epsilon_0\mu_0}}

Who invented the three-phase generator?

Mikhail Dolivo-Dobrovolsky

meaning of first of Maxwell’s equations

Gauss’ law: electric field created around charge

meaning of second of Maxwell’s equations

it is impossible to draw a closed surface thru which there is a non-zero magnetic flux: no individual magnetic charges, only dipoles

meaning of third of Maxwell’s equations

Faraday’s law: changing magnetic field causes electric field

meaning of fourth of Maxwell’s equations

Ampere’s law: changing electric field gives rise to magnetic field

last term of fourth of Maxwell’s equations

Maxwell’s displacement current: changing electric field between plates of discharging capacitor

speed of light in terms of permittivity and permeability of free space

v=\frac{1}{\sqrt{\epsilon_0 \mu_0}}

longitudinal wave definition

direction of vibration parallel to direction of wave

transverse wave definition

direction of vibration perpendicular to direction of wave

wave frequency

how many full wavelengths pass through given point per second

hertz (Hz) definition

1 Hz = 1 wavelength per second

velocity of electromagnetic wave in terms of wavelength and frequency

v=\lambda f or c=\lambda f

\lambda is the wavelength, f is the frequency of the wave, c is the speed of light

electromagnetic spectrum, in order from longest to shortest wavelengths

radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays

visible spectrum definition

400nm (blue) to 700nm (red)

Who discovered X-rays and when?

Wilhem Röntgen in 1895

amplitude modulation (AM)

amplitude of radio wave varied in proportion to frequency of sound wave

frequency modulation (FM)

frequency of radio wave varies with frequency of sound

cathode ray tube (CRT)

a device that accelerates electrons and then magnetically deflects them onto different parts of a screen to create an image

liquid crystal displays (LCDs)

one pixel is actually made of a red, green, and blue component

each pixel has liquid crystal between two glass plates (one vertically polarized, other horizontally polarized), pixel becomes dark when voltage applied

What are diodes often used for? (as mentioned in the Curriculum)

LEDs, convert from AC to DC

What is a light sail?

a large sheet of reflective material that “catches” sunlight like a wind sail

What is one of the most well-known failed experiments to measure a change in the speed of light? (as mentioned in the Curriculum)

Michelson-Morley experiment

Lorentz factor

\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}

v is the velocity of the object, c is the speed of light

purpose of Lorentz factor

tells the difference between how much time you experience versus how much time another observer will experience going at speed v relative to you