Physics Tips 2

mins to hrs

min ÷ 60

how to get kW from W

W ÷ 1000

Cost =

Rate × Energy

how to calculate cost?

1. Get amount of time in hours.

2. Get the kWh

3. Use Cost formula and solve.

how to get kWh?

W = Pt

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What units should cost be in?

R and ^c

what standard must be fulfilled for a voltmeter to read a charge?

If an open switch blocks the path to the battery (open switch on main circuit), the voltmeter is completely disconnected from the power source. With no power reaching it, it reads V = 0.

eV to J

eV × (1,6×10‐¹⁹)

what units is frequency in?

Hz

explain how photoelectric effect provides evidence for the particle nature of light

• If light was a wave, inc of light intensity would result in the emissions of a photoelectron from the metal's surface of a metal for a light of any frequency.

• Because energy would bud up on the metal.

• The fact that electrons are only emitted when freq. inc above a certain level and still emits even if intensity is very low

• proves that if light interacts with metal in discrete bundles that will each only emit electrons if thier energy is enough.

how to format the moment before = to after formula

∑pᵢ = ∑pբ

mₓvₓ ᵢ + mᵧvᵧ ᵢ = mₓvₓբ + mᵧvᵧբ

what to rememebr when explaining force (3rd law)

• must say same force will be experienced

• in an opp direction

• due to Newton’s Third Law

what to remember if object is stopping?

Fₙₑₜ will act in the direction opposite of the obj

when doing work done by force what must you remember? (2)

• units

• use the relevant angle (wether 0/90/180 or a given)

what do motors and generators convert?

motor: electrical to mechanical (fan)

generator: mechanical to electrical

what rule do you use for motors

Flemings Left-hand rule

what rule do you use for generators

right hand rule

where does the middle finger point to

north to south

split ring vs slip ring

DC motor (carbon brushes and battery) vs AC motor (power source and alternating current)

motors in real life (3)

• fans

• electric drills

• washing machine

how to inc magnetic force turning the motors coil

• Increasing the strength of the magnetic field. Instead of using permanent magnets we can use electromagnets (stronger)

• Increasing the current strength in the coil by increasing the emf of the DC power source or decreasing coils resistance (thicker wire)

• Increasing the number of turns in the coil.

INCREASE the MAGNITUDE of the induced current by: (3)

• Moving the conductor faster (this decreases the time)

• Using a stronger magnetic field so stronger magnets

• Increasing the length of the conductor - increase the number of turns (this increases N)

what do B and A represent in magnetic flux formula

• B stands for magnetic field strength (or magnetic flux density. Its standard unit is the Tesla (T).

• A stands for Area. Siize of the flat surface (like a loop, coil, or rectangle) that the magnetic field lines pass through. Its unit is square meters (m²)

Placement and function of the carbon brushes:

• The two carbon brushes are in contact with the slip rings (they are not connected to them).

• These brushes conduct the current induced in the armature (coil) to an external circuit.

Function of the slip rings: (2)

• Establishes contact with the AC Voltage brushes, allowing the current to pass to the external circuit '

• Enable the armature to rotate in the same direction constantly without twisting the wire

Placement and build of slip rings

• Slip rings are each connected to one end of the coil.

• The slip rings are made up of copper bands around insulation rings.

Function of coil and axel and how they relate

• The coil will carry the induced current

• the axel is used to rotate the coil.

• coil (armature) connected to an insulated axel

where do magnets flow?

north to south

label generator

lable generator

what to remember abt the votage of a battery when switch is closed

reflects emf

what to remember when doing emf = Vext + Vint

parrelel V would could as one since repeat

Vint =

I_^T x r

“amount of heat produced”

W is energy

removal of a voltage from parallel

• battery’s voltage would decrease

• lower resistance

• I = V/R (lower resistance leads to inc current)

• EMF and r remain constant

• V_ext decrease

basically whatever to R leads to V_ext

km to m

km x 1000

conservative force ~ (3)

• work done depends only on the starting and ending positions

• Open path: The net work done over a complete round trip (starting and ending at the exact same point) is zero.

W_nc = - ΔE_p

non-conservative force ~ (3)

• A longer or windier route changes the total amount of work done.

• Closed Path: The net work done over a complete round trip is not zero.

W_nc = ΔE_k + ΔE_p

examples of conservative forces (3)

F_g, Elastic/Spring force (F_s), and Electrostatic force.

what can you do when W_nc = 0

E_{m intial} = E_{m final}

examples of non-conservative forces (4)

F_f, Air resistance/Drag, F_t and F_a

what can frequency be seen as

• Strength of the packet

• The frequency of the light (like the color) determines how much energy each individual packet has: Red light photons are too weak. Blue or ultraviolet light photons carry a heavy punch

what can intensity be seen as

• Number of packets

• The intensity (brightness) just means you are throwing more packets, but if the individual packets are too weak (like red light), throwing more of them still won't do the job!

what force always acts straight down

F_g

how to write ΔE_k + ΔE_p easier

½ m (v_f² - v_i²) + mv(h_f - h_i)

how to get θ in work formula

angle between where its going and where it was

what happens when elevator is at constant speed

• scale shows the persons actual weight

how does tension work with triangle shape and it hanging in the middle

W = mg

what happens when internal resistance inc

• V_int increases

• V_ext decreases

• current decreases

EMF = V_ext + v_int

(emf must stay same)

shorter wavelength =

higher kinetic energy

why are bouncing balls lines on the graph parallel to one another?

• Gradient of a velocity–time graph is acceleration.

• The acceleration of the ball is constant as ball is in free fall.

what to place extra attention to when making bouncing ball graph

if the ball stops/start in air or on the ground

why obj in a vehicle accelerate in opp direction of vehicle

• the maximum static frictional forces is insufficient to accelerate the obj with the seat.

a = (two unknows)

Δv/Δt

when can you use short acceleration formula?

when v_i = 0 from t = 0

“energy transferred from obj to what it hit”

ΔE_k = E_k(after) - E_k(before)

km or m for electric field

m

do you use kg or g in electostatics

kg

mC to C

mC x 10^-3

μC to C

μC x 10^-6

nC to C

nC x 10^-9

pC to C

pC x 10^-12

what to remember when’describe the changes in the angle between string and ABC’

angle AND diretion