Physics Unit 1 and 2 Revision Theory

FIA4 revision - Not all of electrical curcuits (unit 1, topic 3) revised.

What are the 4 states of matter?

1. Solid

2. Liquid

3. Gas

4. Plasma

Describe gases:

In a gas, which for a given substance occurs at higher temperatures than its liquid and solid states. The average kinetic energy is high enough that they can break free from bonds holding them together.

Describe liquids:

In a liquid, particles are close together but can move past each other, allowing liquids to take the shape of their container. The average kinetic energy is lower than in gases, resulting in a definite volume but no fixed shape.

Describe solids:

In a solid, particles are closely packed in a fixed arrangement and vibrate in place, giving solids a definite shape and volume. The average kinetic energy is low, resulting in strong intermolecular forces holding the particles in place.

What is Kinetic energy?

The energy a body has due to its motion.

What is internal energy? (U)

the sum of the Kinetic energy of its particles and the potential energy stored in their bonds.

U = K_E + P_E (J)

What is heat?

The transfer of thermal energy through a substance or between substances.

What are the modes of Heat Transfer?

The modes of heat transfer are conduction, convection, and radiation.

Explain conduction:

Conduction is the transfer of heat through direct contact between materials, where faster-moving particles collide with slower-moving ones, transferring energy. This process occurs primarily in solids.

Explain convection:

Transfer of heat in liquids or gases when warmer, less dense fluid rises and cooler fluid sinks; the bulk movement of particles.

Explain radiation heat transfer:

Object emits electromagnetic waves carrying thermal energy. Does not require a medium to travel through.

Kelvin Scale conversion:

T_K = T_C + 273K.

What is absolute zero?

The kelvin scale uses absolute zero. This is the temperature at which the motion of particles should cease.

What is Specific Heat Capacity?

Specific heat capacity is the amount of energy required to raise the temperature of 1kg of a substance by 1 degrees. This is modelled by formula:
Q = mc∆T.

What is Work?

The capacity to do work is described by W = Force (F) x Displacement (s)

Define Temperature:

Temperature is the average kinetic energy of particles in a system.

What is Thermal Equilibrium?

Thermal equilibrium is the state in which two or more interacting systems reach the same temperature, causing no net transfer of heat energy between them. 2 or more objects at different temperatures will eventually reach the same temperature when in contact. Can be described using

-Qlost = Qgained (Joules)

What is latent heat?

During a change of state, energy is added or removed. The energy added or removed during a state change is called latent heat. It can be separated into the Latent Heat of Fusion or the Latent Heat of Vaporisation.

What is Latent Heat of Fusion? (L_f)

The energy required to change the state of 1kg of a substance from its solid state to liquid state without change in temperature.

What is Latent Heat of Vaporisation (L_v)

The energy required to change the stage of 1kg of a substance from liquid to gaseous state.

What are the forces within the nucleus? (what holds it together?)

Is held together by strong nuclear forces. The positive charge of protons causes them to electrostatically repel each other within the nucleus, but is overwhelmed by the short-range attraction of the strong force (all nucleons), causing them to stick.

What is an isotope?

Elements with the same number of electrons and protons but a different amount of neutrons in its nucleus.

What is radioactive decay? (natural)

Radioactive decay is the spontaneous process in which unstable nuclei try to give of excess protons or neurons, emitting radiation in the form of particles or rays. Any radiation that can remove an electron from an atom to create a heavy positive ion and a free electron is called ionising radiation.

Describe Alpha radiation (α):

Alpha radiation occurs when the particle has too much mass. An alpha particle, containing 2-protons and 2-neutrons is ejected. The atomic number (protons) decreases by 2, and mass reduces by four. (p+n)

Describe Beta Positive Radiation (B⁺)

Occurs when the particle has too many protons. A proton transforms into a neutron by emitting a positron and a neutrino. the atomic no (protons) decreases by one and the mass number is unchanged (as proton turned into neutron.) The positron usually destroys an electron producing two gamma rays.

Describe Beta Negative Radiation (B^-)

Occurs when the particle has too many neutrons. A neutron transforms into a proton by emitting an electron and anti-neutrino The Atomic No. increases by one (as neutron transformed into proton) and the mass number is unchanged.

Describe Gamma Radiation

Occurs when there is a unstable or a metastable nucleus in band of stability. The nucleus reshuffles into a more stable (lower energy) configuration emitting a gamma ray. Often occurs immediately or shortly after other types of decay.

What are the properties of nuclear radiation?

1. Ionisation ability

2. Penetrating ability

3. Deflection in electric and magnetic fields

What is ionisation ability?

Ionisation ability is the measure of the ability of radiation to remove electrons from a particle as it passes through it. The higher the ionisation ability, the greater the ability to remove an electron from the atom.

Ionisation ability depends on the size (mass) of the particle. As mass increases, there is higher ionisation ability. Furthermore, the greater the charge, greater ionisation.

What is Penetrating Ability?

Penetrating ability describes how far a type of radiation can travel through matter before being absorbed or stopped. Alpha radiation stops at paper, Beta (both) go through paper and stop at thin woods, aluminum etc., and gamma radiation goes through all except Lead, iron and other thick metal.

What is Deflection in electric or magnetic fields?

As nuclear particles pass through electric and magnetic fields, they are deflected. The extent and direction depends on mass and charge. Beta positive decay moves toward negatively charged plates with great deflection because they are lightweight.

Alpha decay moves towards negatively charged objects, but not to the extent of beta positive (as they are heavier and greater momentum).

Gamma radiation is not affected (no charge or mass) whereas beta negative decay moves toward positively charged plates.

What is a neutrino?

A neutrino is an elementary particle very similar to an electron, but without electrical charge and a samll mass.

How is intensity (cps) found?

I₁/I₂ = (r₂)²/(r₁)²

What is Half-Life?

Half-Life is the time taken for half (on average) of the atoms in a sample of the material to undergo radioactive decay. Longer half-life indicated greater stability. In general, we say that:

N = N_o (1/2)<sup>n

In which N is the number of atoms, No is the initial number of atoms, and n is the number of half-lives. no. of half lives can be given by time elapsed over half life duration. Can be rearranged into different ways to</sup>

What is Artificial Transmutation?

Nuclear reactions can be classifies as either due to natural radioactive decay or artificial nuclear reactions. Artificial nuclear reactions can be induced using artificial transmutation. The most common type is nuclear bombardment in which a proton, neutron, or alpha particle etc. is fired at a nucleus to analyse the particles and nuclei that emerge.

Proton Bombardment:

Firing a proton at a stable nucleus can cause the nucleus to split into two. For example a lithium atom is stable and does not decay naturally. But when a proton is fired at lithium is transmutates into a helium nuclei w/ a flash of gamma energy.

Neutron Bombardment

Another form of artificial transmutation is neutron bombardment. Because they carry no charge they can enter the nuclei easily (more easily) than charged particles

What is binding energy?

Binding energy (energy holding the particles of an atom together) is the energy required to separate the nucleus into its component parts. Energy on the atomic scale is often measured in electron volts.

What is the mass defect?

The masses of nuclei are observed to be slightly less than the sum of their individual parts added together. The missing mass is called the mass defect. A nucleus has less energy than the total energy of its seperated constitutents since some of the energy since some of the energy is released in the formation of the nucleus.

Calculating Binding Energy Tips:

Use the table in the formula book to find the corresponding element's nuclide’s mass. Then find out how many protons, neutrons, and electrons there are, multiply each by its corresponding mass in the formula book, and add them together to get the m(constitutional-parts). Using this info, find the mass defect: Mass defect = m_cp - m_nuclide. Answer in amu.

Multiply mass defect answer by 931.5 MeV to get the binding energy in MeV.

If you need it in Joules, use orignal mass defect, multiply is by x1.66 × 10^-27 kg then use E = mc² as specified below, giving answer in joules. .

To find the binding energy per nucleon, divide the binding energy by the number of protons and neutrons. Give an answer in J/ per nucleon or MeV/ nucleon (depending on which one was asked to figure out.)
_.
Binding Energy: E = mc².

If using amu, instead of kg, 1u = 931.5MeV. Therefore, multiply your amount of amu by 931.5MeV to give the binding energy.

If using kg, find the mass defect in kilograms (mass defect (Δm) × 1.66 × 10^-27), then use E = mc², where m is the mass found and c = 3 × 10^8 m/s. This gives answer in joules. Convert joules to eV by dividing by 1.6×10^-19, then to MeV by / 10⁶.

Mass defect = m_cp - m_nuclide

Explain Nuclear Fission and the chain reaction.

Occurs when the repelling electrical forces within a nucleus overpower the attracting nuclear strong forces. The splitting of atomic nuclei is called nuclear fission. In all known nuclei, the nuclear forces dominate. However, in some elements, such as uranium, this domination is tenuous. One neutron starts the fission, and two to three neutrons are produced when the atom splits. These neutrons can in turn cause the fissioning of 2 of 3 more nuclei, releasing 4 - 9 more neutrons.

This causes a chain reaction succeeding in splitting another atom. Is self-sustaining. The mass of fragments is less than the fissioned nuclei.

Neutron-induced nuclear fission:

Is when Uranium-235 is bombarded with neutrons, causing it to absorb then split, one bigger than the other and producing 3 neutrons (no charge). energy is also produced.

Nuclear Fusion

In nuclear fusion, the colliding particle unites with the parent and fuses into a single nucleus with a higher mass. The new composite nucleus is more stable than the colliding particles. After fusion, the total mass of the nuclei formed is less than that of the mass of the initial nuclei fused.

What’s the law of conservation of charge?

The net amount of charge produced in any transfer is zero.

What is current?

The rate of flow of charge in a circuit. Is described by the equation: I = Q/t

I: Amperes (A)
Q: Couloumbs (C)
t: Time (s)

What is Voltage?

The potential difference. The work done per unit charge measures in volts. Is described by V = W/Q (work = Joules) or V = IR (R: resistance in ohms) Voltage moves from high electric potential to low electric potential, called potential difference in a circuit.

What are conductors?

Conductors need to have charge carriers that can move freely between atoms which are typically electrons. Metals are good conductors since they have a positively charged lattice with a free cloud of electrons which facilitate the movement of electricity.

What are insulators?

Insulators outer electrons are chemically bonded (therefore cant move) to neighboring atoms and therefore electricity cannot freely move.

Ohms Law

Ohm’s law states that the electric current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across those two points, provided the temperature remains constant

Kirchhoff’s 1^st and 2^nd Law

The sum of the currents flowing into a junction must be equal to the sum of the currents flowing away from the junction of wires. (series circuit, current is maintained. Parallel circuits have junctions, so current splits)

The sums of the emfs in any closed loop in a circuit must be equal to the sum of potential differences in the closed loop of the circuit. Meaning the total voltage drop or increase must be zero, as energy is conserved.

Resistance in series and parallel:

R_T = R₁ + R₂ + R₃ …

Power:

The rate of doing work, measured in Watts, W. Given by P = Work (W)/ Time (s) or P = V/t