Assumptions There are a very large number of molecules (N) Molecules have negligible volume compared to the container The molecules show random motion (ranges of speeds and directions) Newton’s Laws of Motion can be applied to the molecules Collisions are elastic and...
Gas Properties Volume, V: This is the space occupied by the particles that make up the gas. Volume is measured in metres cubed, m3 Temperature, T: This is a measure of the internal energy of the gas and this is equal to the average kinetic energy of its particles....
Internal Energy The internal energy of a substance is due to the vibrations/movement energy of the particles (kinetic) and the energy due to the bonds holding them together (potential). Solids: In a solid the particles are arranged in a regular fixed structure, they...
Specific Heat Capacity We know that when we heat a substance the temperature will increase. The equation that links heat (energy) and temperature is: c is the specific heat capacity which is the energy required to raise the temperature of 1 kg of a substance by 1...
Making Electricity This is a typical nuclear fission reactor. A nuclear power station is similar to a power station powered by the combustion of fossil fuels or biomass. In such a station the fuel is burnt in a boiler, the heat this produces it uses to heat water into...
Nuclear Reactor Safety There are many safety features and controls in place designed to minimise the risk of harm to humans and the surrounding environment. Fuel Used Using solids rather than liquids avoids the danger of leaks or spillages. They are inserted and...
The nucleons move closer together à potential energy is lost à energy is given out.
Decay (Also seen in GCSE Physics 1) Something that is radioactive will decay into something that is stable. Radioactive decay happens randomly and spontaneously: there is no way of predicting when a radioactive nucleus will decay and external factors do not influence...
Results (Also seen in GCSE Physics 2) Geiger and Marsden found that almost all of the alpha particles passed through with little or no deflection. Rutherford suggested moving the microscope in front of the foil, when they did they found that about 1 in every 8000 was...
Transformers (Also seen at GCSE Physics 3) A transformer is a device used to change the voltage/current of a circuit using electromagnetic induction. It consists of a soft iron core wrapped on both side with wire. The first coil of wire is called the primary coil and...
Making Electricity (Also seen at GCSE Physics 3) An e.m.f. can be induced across the ends of a conducting wire in two ways: 1) Move the wire through a magnetic field or 2) Move a magnet through a coil of the wire In both cases magnetic field lines and...
The Cyclotron A cyclotron is a particle accelerator. It consists of two hollow D-shaped electrodes (called ‘dees’) that are attached to an alternating p.d. supply. The dees are placed in vacuum chamber and a magnetic field which acts at right angles to...
We will be looking at the force a current carrying wire experiences when it is in a magnetic field. Before we look into the size and direction of the force we need to establish some basics. Conventional Current We know that the current flowing in a circuit is due to...
Quantitative Treatment We could use the graph above to find the charge on the capacitor after a time, t. We could also use it to find the time it takes for the charge to fall to a value of Q. This requires the graph to be drawn very accurately and values...
In the diagram to the right a capacitor can be charged by the battery if the switch is moved to position A. It can then be discharged through a resistor by moving the switch to position B. Charging a Capacitor When the switch is moved to A the battery sends...
Motion in an Electric Field A charged particle moving through an electric field will feel a force towards the oppositely charged plate. We see that the electron moves in a parabola towards the positive plate and the positron moves towards the negative plate. ...
Charging and Discharging When a capacitor is connected to a battery is sends out electrons to one of the plates, this becomes negatively charged. The same amount of electrons move from the second plate and enter the battery, leaving the plate positively charged. The...
Coulomb’s Law (Electric Force) (Also seen in GCSE Physics 2) The electrostatic force acts between all charged particles and can be attractive or repulsive. It is the charges themselves that cause the force to exist. The force that acts between two charges, Q1 and Q2,...
Graphs Here are the graphs of how gravitational field strength and gravitational potential vary with distance from the centre of a mass (eg planet). In both cases R is the radius of the mass (planet).
Orbits (Also seen in GCSE Physics 3) For anything to stay in orbit it requires two things: *A centripetal force, caused by the gravitational force acting between the object orbiting and the object being orbited *To be moving at a high speed We now know equations for...
Newton’s Law of Gravitation (Gravity) (Also seen in GCSE Physics 3) Gravity is an attractive force that acts between all masses. It is the masses themselves that cause the force to exist. The force that acts between two masses, m1 and m2, whose centres are separated...
Free Vibration Free vibration is where a system is given an initial displacement and then allowed to vibrate/oscillate freely. The system will oscillate at a set frequency called the natural frequency, f0. We have seen from the last lesson that the time period for a...
Pendulum Consider the simple pendulum drawn below. When released from A the bob accelerates and moves to the centre point. When it reached B it has reached a maximum velocity in the positive direction and then begins to slow down. At C it has stopped completely so the...
Oscillations In each of the cases below there is something that is oscillating, it vibrates back and forth or up and down. Each of these systems is demonstrating Simple Harmonic Motion (SHM). SHM Characteristics The equilibrium point is where the object comes to rest,...
Moving in a Circle (Also seen in GCSE Physics 3) For an object to continue to move in a circle a force is needed that acts on the object towards the centre of the circle. This is called the centripetal force and is provided by a number of things: For a satellite...
To the right is the path a car is taking as it moves in a circle of radius r. Speed is measured in metres per second, m/s or m s-1
This states that the force is a measure of change of momentum with respect to time. This is Newton’s Second Law of Motion: The rate of change of an object’s linear momentum is directly proportional to the resultant external force. The change in the momentum takes...
Diffraction When waves pass through a gap they spread out, this is called diffraction. The amount of diffraction depends on the size of the wavelength compared to the size of the gap. In the first diagram the gap is several times wider than the wavelength so the wave...
Since momentum is conserved the total momentum before the crash = the total momentum after the crash. The total momentum before is the momentum of A + the momentum of B The total momentum after is the new momentum of A + the new momentum of B We can represent this...
Interference Interference is a special case of superposition where the waves that combine are coherent. The waves overlap and form a repeating interference pattern of maxima and minima areas. If the waves weren’t coherent the interference pattern would change rapidly...
Bending Light When light passes from one material to another it is not only the speed of the light that changes, the direction can change too. If the ray of light is incident at 90° to the material then there is no change in direction, only speed. It may help to...
Total Internal Reflection (Also seen in GCSE Physics 3) We know that whenever light travels from one material to another the majority of the light refracts but a small proportion of the light also reflects off the boundary and stays in the first material. When the...
Superposition Here are two waves that have amplitudes of 1.0 travelling in opposite directions: Stationary/Standing Waves When two similar waves travel in opposite directions they can superpose to form a standing (or stationary) wave. Here is the experimental set up...
Waves All waves are caused by oscillations and all transfer energy without transferring matter. This means that a sound wave can transfer energy to your eardrum from a far speaker without the air particles by the speaker moving into your ear. We will now look at the...
Waves All waves are caused by oscillations and all transfer energy without transferring matter. This means that a water wave can transfer energy to you sitting on the shore without the water particles far out to sea moving to the beach. Here is a diagram of a wave; it...
The Young Modulus, E The Young Modulus can be thought of as the stiffness constant of a material, a measure of how much strain will result from a stress being applied to the material. It can be used to compare the stiffness of different materials even though their...
Deforming Solids Forces can be used to change the speed, direction and shape of an object. This section of Physics looks at using forces to change of shape of a solid object, either temporarily or permanently. If a pair of forces are used to squash a material we say...
Density, ρ Density is the mass per unit volume of a material, a measure of how much mass each cubic metre of volume contains. Density if given by the equation: Where ρ is density, m is mass in kilograms and V is volume in metres cubed. Density is measured in...
Hooke’s Law If we take a metal wire or a spring and hang it from the ceiling it will have a natural, unstretched length of l metres. If we then attach masses to the bottom of the wire is will begin to increase in length (stretch). The amount of length it has increased...
Energy (Also seen in GCSE Physics 1) We already know that it appears in a number of different forms and may be transformed from one form to another. But what is energy? Energy is the ability to do work. We can say that the work done is equal to the energy transferred ...
Energy Transformations (Also seen in GCSE Physics 1) We already know that energy cannot be created or destroyed, only transformed from one type to another and transferred from one thing to another. Eg a speaker transforms electrical energy to sound energy with the...
Acceleration Due To Gravity (Also seen in GCSE Physics 2) An object that falls freely will accelerate towards the Earth because of the force of gravity acting on it. The size of this acceleration does not depend mass, so a feather and a bowling ball accelerate at the...
Newton’s 1st Law An object will remain at rest, or continue to move with uniform velocity, unless it is acted upon by an external resultant force. Newton’s 2nd Law The rate of change of an object’s linear momentum is directly proportional to the resultant external...
Before we look at the two types of graphs we use to represent motion, we must make sure we know how to calculate the gradient of a line and the area under it. Gradient We calculate the gradient by choosing two points on the line and calculating the change in the y...
In the last lesson we looked at how we could add vectors together and find the resultant. In this lesson we will first look at ‘breaking down’ the vectors and then finding the equilibrium. Resolving Vectors A vector can be ‘broken down’ or resolved into its vertical...
What is a Vector? A vector is a physical quantity that has both magnitude (size) and direction. Examples of Vectors: Displacement, velocity, force, acceleration and momentum. What is a Scalar? A scalar is a physical quantity that has magnitude only (it doesn’t act in...
The Oscilloscope An oscilloscope can be used to show the sizes of voltages and currents in both d.c. and a.c. circuits. This is what a typical oscilloscope looks like. A trace would be seen on the grid display. D.C. Traces (Also seen in GCSE Physics 2) If we connected...
Energy is conserved in all circuits, for any complete circuit the sum of the emfs is equal to the sum of the potential differences. Energy givers = energy takers. In the diagram we can say that: ε = pd1 + pd2 + pd3 + pd4. Uses In...
ACDC Definitions (Also seen in GCSE Physics 2) Direct Current Cells and batteries are suppliers of direct current; they supply an emf in one direction. In the graph below we can see that the current and voltage are constant. The bottom line shows that when the battery...
Fuses (Also seen in GCSE Physics 2) Electrical devices connected to the Mains supply by a three-pin plug have a fuse as part of their circuit. This is a thin piece of wire that melts if the current through it exceeds its maximum tolerance. The common fuses used are...
Energy in Circuits In circuits there are two fundamental types of component: energy givers and energy takers. Electromotive Force (emf), ε Energy givers provide an electromotive force, they force electrons around the circuit which transfer energy. The size of the emf...
Series Circuits (Also seen in GCSE Physics 2) In a series circuit all the components are in one circuit or loop. If resistor 1 in the diagram was removed this would break the whole circuit. Parallel Circuits (Also seen in GCSE Physics 2) Components in...
Resistance The resistance of a wire is caused by free electrons colliding with the positive ions that make up the structure of the metal. The resistance depends upon several factors: Length, l...
Ohm’s Law (Also seen in GCSE Physics 2) After the last lesson we knew that a voltage (or potential difference) causes a current to flow and that the size of the current depends on the size of the p.d. For something to obey Ohm’s law the current flowing is proportional...
Definitions (Also seen in GCSE Physics 2) Current, I Electrical current is the rate of flow of charge in a circuit. Electrons are charged particles that move around the circuit. So we can think of the electrical current is the rate of the flow of electrons, not so...
Two years after de Broglie came up with his particle wavelengths and idea that electrons could diffract, Davisson and Germer proved this to happen. They fired electrons into a crystal structure which acted as a diffraction grating. This produced areas of electrons and...
It can do this by another electron colliding with it or by absorbing a photon of the exact energy. When moving down a level the electron must lose the exact amount of energy when making the transition. It releases this energy as a photon of energy equal to the energy...
Observations When light fell onto a metal plate it released electrons from the surface straight away. Increasing the intensity increased the number of electrons emitted. If the frequency of the light was lowered, no electrons were emitted at all. Increasing the...
Feynman Diagrams An American Physicist called Richard Feynman came up with a way of visualising forces and exchange particles. Below are some examples of how Feynman diagrams can represent particle interactions. The most important things to note when dealing with...
Strangeness The weak interaction is the only interaction that causes a quark to change into a different type of quark. In beta decay up quarks and down quarks are changed into one another. In some reactions an up or down quark can change into a strange quark meaning...
The Strong Interaction The strong nuclear force acts between quarks. Since Hadrons are the only particles made of quarks only they experience the strong nuclear force. In both Baryons and Mesons the quarks are attracted to each other by exchanging virtual particles...
The Four Interactions There are four forces in the universe, some you will have come across already and some will be new: The electromagnetic interaction causes an attractive or repulsive force between charges. The gravitational interaction causes an attractive force...
Made from Smaller Stuff Hadrons, the Greek for ‘heavy’ are not fundamental particles they are all made from smaller particles, quarks. The properties of a hadron are due to the combined properties of the quarks that it is made from. There are two categories of...
Fundamental Particles A fundamental particle is a particle which is not made of anything smaller. Baryons and Mesons are made from quarks so they are not fundamental, but quarks themselves are. The only other known fundamental particles are Bosons (see Lesson 6:...
Rutherford Also seen in GCSE Physics 2 Rutherford fired a beam of alpha particles at a thin gold foil. If the atom had no inner structure the alpha particles would only be deflected by very small angles. Some of the alpha particles were scattered at large angles by...
Antimatter British Physicist Paul Dirac predicted a particle of equal mass to an electron but of opposite charge (positive). This particle is called a positron and is the electron’s antiparticle. Every particles has its own antiparticle. An antiparticle has the same...
The Nuclear Model (Also seen in GCSE Physics 1 and 2) We know from Rutherford’s experiment that the structure of an atom consists of positively charged protons and neutral neutrons in one place called the nucleus. The nucleus sits in the middle of the atom and has...