unit one and two physics atar

potential difference

the difference in electrical charge between two points in a circuit expressed in volts

Residual Current device

an electrical safety component that compare the active and neutral wires in a house, if there's a difference the rcd detects it and switches off in milliseconds (detects differences of 50mA or greater)

Earth wire

the wire in a mains cable used to connect the metal case of an appliance to earth

Fuse

A thin piece of wire that melts causing an open circuit if current flowing through it is too high must be replaced

Circuit breakers

uses an Electromagnetic switch that will bend away from circuits if current flows at too high of a value into your house. high current generates a magnetic field strong enough to attract a metal element in switch system, making it turn off at a chosen threshold

Work and power equations

Work= energy

Number of electrons formula

n = Q/e

Charge is measured in

Coulombs, C

Energy formula

Power x time

conservation of momentum formula has no net force

p=mv is used in totalmvi= totalmvf

derived formula if two objects stick together; m1v1 + m2v2 =(m1 + m2)vf

use formula for collisions and explosions

objects not sticking together; m1vi1 +m2vi2= m1vf1 + m2vf2

Net Force & Acceleration formula

net force= ma

acceleration is always direction of net force

can be rearranged to find each use when You see forces (pushes, friction, tension) and acceleration

use for free body diagrams

Impulse & Momentum

you see contact time delta t, changing speeds, bouncing, or a force–time graph *area=impulse.

• delta p= mvf-mvi = f delta t

delta p = kms-1

impulse = Ns

moment + impulse combined f=ma and delta p

fnet= mvf-mvi/ delta t

use formula for force of impact, contact/ breaking time, impulse/ change in momentum

change in momentum 2 dimensional questions

may need to solve equations using vector addition

e.g I=mfvf-mivi

vector addition; e.g mfvf + (-mivi) also give direction to the vectors

inclined plane rules

mgcos - perpendicular

mgsin- parallel

fnet= mgcos

Ffriction= mgsin

static friction- surfaces not sliding

kinetic friction- surfaces sliding

•         Friction then = μ mg cos θ, acting up the slope if the object slides down.

•         Net force down the slope (sliding down): ΣF = mg sin θ – μ mg cos θ.

How are non earth wired appliances safe

Double insulated -wires inside are insulated and the device has a non conductive casing (no earth connection)

Why voltmeter has little impact on current or voltage

It has ideally infinite resistance

strong force

force of attraction between quarks which make up protons and neutrons

remnant force (residual strong force)

extends a short distance beyond a proton or neutron that is a very strong attractive force between protons and neutrons

nucleus of an atom

dominated by electromagnetic (repulsive) and the strong nuclear force (attractive)atoms are typically stable if these forces are balanced

quarks

particles of matter that make up protons and neutrons

Colour confinement

A physics rule stating that quarks can never exist alone. When pulled apart, the energy stretching between them snaps and transforms into a brand-new pair of quarks, following Einstein's equation ((E=mc^2)).

proton quarks

up up down (UUD)

neutron quarks

up down down (UDD)

positron

a positively charged electron

neutrino

an elementary subatomic particle with no electric charge and an extremely small, non-zero mass.

antineutrino

the antiparticle of the neutrino

calculating the amount of neutrons in an atom

Neutrons=Mass Number−Atomic Number

beta minus decay

nucleus has too many neutrons to be stable in this process a neutron (UDD) spontaneously changes into a proton (UUD)

beta minus decay process

a proton turns into a neutron, a positron and a antineutrino

beta plus decay

when a nucleus has too many protons, a proton may spontaneously change into a neutron, a positron and a neutrino

gamma decay

radioactive decay by emission of a gamma ray

half life

the time taken for half of a substance to undergo a decay process

absorbed dose

the amount of energy deposited by ionizing radiation per unit mass of a substance or tissue equivalent to 1J/KG

equivalent dose

the measure of biological damage from an absorbed dose that has been adjusted for the type of radiation measured in Sv

radioisotope

a specific version of a chemical element that has an unstable nucleus, causing it to release radiation as it breaks down to become stable

mass defect

the difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons

Uranium-238 consists of 92 protons and 146 neutrons. The mass of a U-238 nucleus is less than the sum of the masses of its protons and neutrons. Explain why

When an atom is formed, mass is converted to "binding energy" which is released. This
energy has a mass equivalence and is known as the mass defect

Alpha radiation has the highest ionising ability of all types of radiation.

Alpha radiation has the highest ionising ability of all types of radiation.
Explain what is meant by the term "ionising radiation

Ionising radiation is energetic enough to strip electrons from atoms (or break molecular
bonds) of matter is passes through. i.e. ionizing radiation produces ions.

What would be the effect on the power output if the control rods were slowly pushed into the reactor core? Explain.

Boron is an excellent neutron absorber. Pushing the control rods deeper into the core means they will absorb more neutrons.
The Chain Reaction: With fewer neutrons available to hit other Uranium-235 atoms, the rate of fission reactions slows down, which lowers the overall thermal energy and power output.

The engineers did not include a moderator in the core. Explain how this would affect the operation of the nuclear reactor

The moderator slows neutrons down to improve the chance of U-235 capturing the neutron and undergoing fission. Not including a moderator may result in the chain reaction not sustaining fast neutrons move too quickly to reliably drop into the nucleus

reactor core operations and functions

Control Rods → Absorb neutrons → Controls rate of reaction. Moderator → Slows down fast neutrons → Makes them thermal / easier to capture.

Fission → Splitting a heavy nucleus → Releases energy and fast neutrons.

Moderator → Slows down fast neutrons → Makes them thermal / easier to capture

alpha particle charge

+2e

beta minus particle charge

-1e

beta plus particle charge

+1e

gamma particle charge

0 (neutral)

effects of ingesting gamma radiation

exposes your internal organs directly to high-energy, penetrating rays that destroy cellular DNA and cause acute radiation sickness increased risk of cancer

fast neutrons

Created instantly by fission. They travel too fast (~20,000 km/s) and just ricochet off Uranium-235 without splitting it.

slow thermal neutrons

Slowed down to ~2 km/s. Traveling slowly gives the Uranium-235 nucleus a high cross-section (chance) to capture them, triggering fission.

water moderator

Liquid water acts as both a moderator and absorber because its light hydrogen atoms mirror the exact mass of a neutron. This unique atomic matching allows water to efficiently slow down fast neutrons while also permanently trapping excess ones.

graphite moderator

Graphite acts only as a moderator because its heavy carbon atoms simply bounce and slow down neutrons without absorbing them. It efficiently creates slow neutrons to feed fission but completely lacks the safety sponge ability to trap excess ones.

fissile

Can easily split when hit by a slow, low-energy neutron. These are rare, heavy isotopes.

fissile materials example

Uranium-235 (²³⁵U) Plutonium-239 Uranium-233 (²³³U)

What is fission?

Fission splits a massive element into fragments, releasing energy in the process.

What is fusion?

Fusion joins two light elements, forming a more massive element, and releasing energy in the process.

Why do fission and fusion both release energy?

They both release energy because of the binding energy per nucleon curve.

why are higher temps needed for fusion

atomic nuclei move fast enough to crash past their electrical repulsion and fuse.

binding energy

The energy needed to break up a nucleus into its constituent nucleons.

Process of fusion

The Fuel: Usually uses deuterium and tritium (two types of heavy hydrogen).The Barrier: Positive charges naturally push the nuclei apart.The Solution: Extreme heat and pressure force them together, overcoming the repulsion.The Result: The lost mass from the collision converts into pure energy ((E=mc^2)

ave speed

distance over time

ave velocity

displacement over time

change in a variable

final- initial