ACTUALLY surviving physics 2

thermodynamics

exchange of heat energy between bodies and the conversion of heat energy

temperature

average kinetic energy of the atoms withina system;measure of internal energy

kinetic energy

K= 3/2k_bT or 3/2nRT = 1/2mv²

maxwell-bolton distribution

graph of the speed average

when speed increases, graph flattens on the right

when it decreases, it scooches up on the left

ideal gas

has random instantaneous velocities of its atoms

negligible volume

random elastic collisions

only forces during collisons matter

density and pressure are constant at all points

pressure of an ideal gas is the  same everywhere

no potential energy

ideal gas law

PV= nRT

Heating

transfer of energy into a system

Cooling

transfer of energy out of a system

Conduction

Convection

radiation

where does energy flow

most likely from high temperature to low temperature

transferred until systems are the same temperature

thermal equilibrium

when no net energy is transferred between 2 systems

internal energy(U)

Q+W= 3/2 nRt

Equal to sum of all kinetic energy in the system

Change in internal energy leads to change in internal structure and behavior of a system

First law of thermodynamics

U = Q+W

In an isolated system the total energy is constant

In a closed system, the change in internal energy is the sum of energy transferred to the system by heating + work

Thermal work

W = -P* change in V

Pressure volume graphs

Represent thermodyanmic processes

Work = area underneath curve

isovolumetric/isochoric

constant volume

isothermal

constant temperature

isobaric

constant pressure

adiabatic

no energy transferred

Energy required to change temperature

Q=mc*change in T

c = specific heat

Rate at which energy is transferred by conduction

Q/change in t= (kA*change in T)/L

k = Thermal conductivity

A = area

T = temperature

L = length

Second law of thermodynamics

total entropy of an isolated system never decreases and is constant when all processes a system goes under are reversible

entropy

tendency of energy to spread/unavailability of a system’s energy to do work

maximized in thermal equilibrium

isolated systems move toward thermal equilibrium

entropy of an isolated system never decrases, but in a closed system it can decrease due to energy being transferred in our out

Charge

positive/negatie quantity of all matter

Electron have -e, protons have +e, neutrons have no charge

Coloumbs law

k or 1 /4pi epsilon not * q1q2/r²

direction of force

opposites attract, likes repel

electric permittivity

measure of the degree to which a material/medium is polarized in the prescence of an electric field

electric polarization

rearrangement of electrons by an external electric field

Constant in free space

Net charge

changes due to transfer of charge(electrons) between a system and its surroundings

Grounding

connecting a charged system to a larger neutral system

Electric field

ratio of electric force to charge

E=fe/q or E= V/r

acts positive; points away from positive charges and towards negative charges

measured in N/C

electrostatic equilibrium

charge of a conductor is distributed on surface; electric field is 0

electric field is perpendicular to surface of a conductor

electric field is same at every point in the sphere and 0 at the center

insulator has charge distributed inside and on the surface

electric potential energy

equal to work required for an external force to bring the point charges to their current position from infinitely far away

Ue=kq1q2/r

Measured in joules

Electric potential

electric potential energy per unit charge

V= k*sum of (q/r) or Ue/q

Measured in volts

electric potential difference is change in electric potential energy when a test charge is moved between 2 points

Isolines

lines of electric potential in space

electric field is stronger when closer together

stronger for negatives lower for positives

Capacitors

two separated parallel conducting surfaces that can hold equal amounts of charge with opposite signs

Capacitance

C=Q/V

Depends on capacitor

For parallel plates with a dielectric in the middle

C = K(epsilon not) * A/d

Measured in farads

Electric field of a capacitor

Ec= Q/k(epsilonnot)A

Electric potential energy of a capacitor

Uc= 1/2QV

Conservation of electric energy

Ue= qV

Current

the rate at which charge passes through the cross-sectional area of a ire

I= q/t

Measured in amperes

Moves in the direction of positive charge

Circuit

composed of electrical loops which can include elements such as wires, batteries, resistors, lightbulbs, capacitors, switches, ammeters, and voltmeters

Closed electrical loop

closed path where charges can flow

Closed circuit

a circuit where charges can flow

Open circuit

one where charges can’t flow

short circuit

charge can flow with no potential difference

Circuit elements

battery, bulb, switch, capacitor, resistor, ammeter, voltmeter

Resistance

measure of the degree an object opposes the movement of electric charge

R = pl/A(resistor with uniform geometry)

p = resistivity

l = length

A = area

Measured in ohms

Ohm’s law

I = V/R

Ohmic material

A material with constant resistance for all currents and constant resistivity for all temperatures

Electric power

P = IV

P = I²R = V²/R

Brightness of a bulb increases with power

Series connection

connection where charges must pass through all elements with no other paths available; current in each element must be the same

R = sum of all Rs

parallel connection

Connection where charges will flow through one of multiple paths

1/R = sum of 1/R

Resistance of the group decreases

Ideal batteries and wires

negligible resistance

nonideal battery

resistance like a resistor in series with an ideal battery and remainder of the circuit

Potential difference(V) = E(emf)- Ir

Ammeter

used to measure current at a specific point in a circuit; must be in series and have 0 resistance

nonideal if it changes properties of circuit being measured

Voltmeters

used to measure potential different beteen two points; must be connected in parallel and have infinite resistance

nonideal if it changes properties of circuit being measured

Kirchoff’s loop rule

potential difference of all circuit elements in a closed loop must equal 0

Kirchhoff’s junction rule

Current entering a junction must equal that leaving a junction

Capacitors in series

1/C

Capacitors in parallel

C

Time constant of an Rc circuit

measure of how quickly a capacitor will charge/discharge

tau  = Req*Ceq

Charging capacitor time constant

time required for capacitor charge to increase from 0 to 63 percent

Discharging capacitor

time required for capacitor charge to decrease from fully charged to 37 percent

Potential difference and current of a capacitor

Charges but steadies over time

Magnetic field

a vector field that can be used to determine magnetic force exerted on moving electric charges, electric currents, or magnetic materials

produced by dipoles 

north and south polarity

form closed loops

decreases getting farther away from the dipole

points away from north pole, towards south

earth is a dipole

perpendicular to velocity and position of an object

magnitude is max when velocity vector is perpendicular

independent from electric field

permanent magnetism

ferromagnetic materials 

induced/weak magnetism

paramagnetic materials

dimagnetism

electronic structure is weakly aligned with dipoles

magnetic permeability

measurement of the amount of magnetization in a material in response to an external magnetic field

free space

constant magnetic permeability uo

magnetic force

exerted by a field on a charged object

F=qvBsin0

B = magnetic field

Hall effect

describes potential difference created in a conductor by an external magnetic field that has a component perpendicular to the direction of charges moving in the conductor

magnetic field of a current carrying wire

B= uoI/2pir

Direction with the right hand rule

multiple with vectors

magnetic force on a current carrying wire

F=IlBsin0

I = current

l = length

light ray

straight line that is perpendicular to the wavefront of a light wave and points in the direction the wave travels

law of reflection

the angle between the indirect ray(when it touches the surface) and the normal line(line perpendicular to the surface) is equal to the angle between the reflected ray and normal line

diffuse reflection

the reflection of light from a rough surface, resulting in light being reflected in many directions

specular reflection

the reflection of light from a smooth surface, resulting in light uniformly reflected from the surface

focal point

the common location that incident light rays gather

focal length

distance from lens to the focus; specific to different lens

plane mirrors

only produce upright and virtual images that are the same size as the object and same distance behind the mirror as the object is in front

infinite focal length

concave mirror

a converging mirror where all the rays gather towards one point; positive focal length

real images form in front of the mirror and can be projected, while virtual form behind and cannot be projected

focal length = R/2

convex mirror

a diverging mirror where all the rays reflect in different directions; negative focal length

image is always smaller than the object and behind the mirror; upright and virtual

focal length = -R/2

spherical mirror

focal point located between principal axis of the mirror halfway between the surface of the mirror and the center of the mirror’s radius of curvature

real image

formed by a mirror when light rays coming from a common point are reflected and intersect at a common point

virtual image

formed by a mirror when light rays diverge to look like they originated from a common point

Location of an image

distance between the image and mirror = distance between the object and mirror

Magnification of an image

ratio of size/height of the image formed by the object and the size/height of the object itself

if greater than 1, the image is enlarged

if less than 1, image is reduced

ray diagrams

used to determine ray location, type, size, and orientation formed by mirrors

important rays: parallel to the principal axis, the ray that reflects at the center of the mirror, the ray that passes through the focal point

refraction

a result of the speed of light changing when light enters a new medium

index of refraction

value showing how prone a medium is to refraction

n=c/v

Snell’s law

relates incidence angles and refraction of a light ray passing from one medium to another

when a light ray travels from a medium with a higher index of refraction into a medium with a lower index of refraction, the ray refracts away from the medium, and vice versa

when a light ray is incident along the normal, the ray is not refracted

total internal reflection

occurs when light passes from one medium into another with a lower index of refraction; occurs at the critical angle of incidence

critical angle

at the critical angle, incident rays refract at 90 degrees and travel along the surface of the material; beyond it all light is reflected

sign conventions

positive focal length; convex

negative focal length; concave

positive image distance; real

negative image distance; virtual

positive image height; upright

negative image height; inverted

thin lens equation

wave

transfers energy WITHOUT TRANSFERRING MATTER between two locations