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74 Cards in this Set
- Front
- Back
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What is a gravitational field?
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A region of space where a mass experiences a force due to the presence of another mass.
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Which four fundamental interactions are there and what do they act on?
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Gravitational force - acts on mass
Electromagnetic force - acts on electric charge Strong force - acts on nuclear particles Weak force - acts on most elementary particles |
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What are electromagnetic fields?
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The forces acting between charged particles. They are repulsive or attractive.
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What is g?
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The magnitude of a gravitational field
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What is Newton's law of universal gravitation?
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All mass attracts all other mass with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
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What is G? Is it a variable or a constant?
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6.67 x 10^-11, constant
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What is V in gravity? Is it a variable or a constant?
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Gravitational potential energy. It is potential energy per unit of mass for an object. It is a variable.
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What is escape velocity?
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The minimum energy a mass needs to escape the gravitational field and reach infinity.
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What is the velocity of an object given escape velocity at infinity?
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0
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What is T when referring to satellites?
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The satellite's period.
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What is required for geosynchronous orbit?
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A period of 24 hours.
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Which way do field lines go in an electrostatic force diagram?
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Away from positive charge and towards negative charge.
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What is V in electrostatics?
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The amount of work done in moving a unit positive charge from infinity to that point.
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Materials that don't hold magnetism when removed from a magnetic field are called?
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Soft magnets
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Materials that hold magnetism when removed from a magnetic field are called?
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Hard magnets
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What materials are magnets often made of?
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Ferromagnetic materials
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What is it called when a material remains magnetised?
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Remanence
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Fleming's left hand rule:
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First finger - Field
seCond finger - Current thuMb - Motion |
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What is B? Is it a variable or constant?
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B is magnetic field strength. It is a variable.
It is the force per unit length per unit current on a current-carrying conductor at right angles to the direction of the magnetic field. |
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What is the SI unit of B?
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The Tesla (T)
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What is the strong force?
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The subatomic glueing force that acts between subatomic particles to keep like charges from flying apart. It has a very short range.
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What is the study of static electricity called?
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Electrostatics
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What is a conservative field?
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The energy transferred when a charge moves between two points is independent of the path taken.
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What can the electric field strength between two charges be influenced by?
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Dielectrics and the medium between them. (epsilon r)
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What are the differences between electrical fields and gravitational fields?
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- The force may be attractive or repulsive for electrical fields
- The electrical fields are much stronger than gravitational fields - Potential electric energy is negative and potential gravitational energy is positive. - Potential is negative for electrical fields and positive for gravitational field. |
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What does Einstein say in his general theory of relativity about gravitational fields?
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That gravitational fields are different from magnetic and electrical fields even though the mathematical relationships are the same. Gravitational fields are warps or distortions of space.
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What kind of relationship does Force vary by?
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An inverse square law.
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What is one coulomb of charge defined as?
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The charge on 6.25 x 10^18 electrons.
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What is one ampere defined as?
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1 Coulomb per second.
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What units does electric field strength have?
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Newtons per coulomb (N C^-1)
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What units does gravitational field strength have?
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Newtons per kilogram (N Kg^-1)
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What units does gravitational potential have?
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J Kg^-1
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What units does electrical potential have?
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J C^-1
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What is F=BqvsinX
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The force on a charge moving in a magnetic field.
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What is electromagnetic induction?
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The use of magnetic fields to produce electricity.
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How can the magnitude of the current be effected?
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By the speed of movement of the magnet, the strength of the magnet and the number of loops in the conductor.
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What is the current caused by in electromagnetic induction?
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The created e.m.f across the ends of the wire.
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What is mutual induction?
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Where a pulse of current in a primary conductor causes an e.m.f across the ends of a secondary conductor.
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What is magnetic flux (theta)?
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The flow of magnetism in a magnet or around a wire carrying current.
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What is magnetic flux measured in?
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Webers (Wb)
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How can an e.m.f be induced in terms of magnetic flux?
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1. By keeping flux density constant (Magnetic field strength) and changing the area enclosed by the circuit.
2. By keeping the area enclosed by the circuit constant and changing the flux density. |
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What is Faraday's law of electromagnetic induction?
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The e.m.f induced in a circuit is directly proportional to the rate of flux cutting or the change in flux linkage through the circuit.
epsilon=Blv |
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What are transformers used for?
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The stepping up and stepping down of voltage in an electrical grid.
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What does a transformer consist of?
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A primary and secondary coil wound around two ends of a magnetically soft material.
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Is there an electrical connection between the coils?
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No but the e.m.f produced in the primary coil causes an e.m.f to be produced in the secondary coil.
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When does a nucleus release gamma rays?
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When it is in an excited state after releasing alpha or beta particles.
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What is binding energy?
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The energy released when nucleons are brought together from infinity to form the nucleus.
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What is the mass defect?
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The difference in mass between the individual nucleons and the atom.
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How does fission occur?
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The incoming neutron distorts the nucleus so that parts of the nucleus move far away enough for the electromagnetic force repulsing the protons overcoming the strong force holding them together.
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What factor must exist for the chain reaction in fission to be self-sustaining?
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The material to exceed critical mass.
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What rate does fission occur at when the reactor is at critical state?
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Constant
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What kind of light is required for the escape of electrons from a metal surface?
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Ultraviolet or smaller.
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What are liberated electrons called (liberated by ultraviolet light)?
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Photoelectrons
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What is the minimum frequency of light required for the photoelectric effect to occur?
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The threshold frequency.
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Does the rate of photoelectrons emitted depend on the frequency?
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No it depends on the intensity of the light.
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In the equation for the photoelectric effect, what does hf represent?
What does theta represent? |
The energy of the photon of U.V light.
The work function of the metal. |
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What is a photomultiplier tube used for and how does it do this?
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It detects light. A photon causes a pulse of current to flow through an external circuit due to the created avalanche of photoelectrons.
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What are the practical applications of the photoelectric effect?
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Light detection in fiber optics
Photosynthesis in plants Photomultipliers are used in low levels of light. |
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What are the experiments in particle accelerators called?
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Scattering experiments.
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What was the first accelerator? What particle energy would it enable to be produced? What is a feature of it? What are the disadvantages?
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The linear accelerator. GeV energies. It had drift tubes to accelerate the particles. The alternating current in the drift tubes causes a force on the charge to move it forward. The linear accelerator is very space consuming because it has to be very long to speed up the protons to the required velocity.
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What is the cyclotron and what are its advantages over a linear accelerator?
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The cyclotron uses two large poles of a magnet and two large D shaped electrodes. It causes protons to gain velocity and spiral out as they pick up speed.
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How are the D shaped electrodes used?
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An alternating potential is applied across the electrodes. This changes at exactly the right frequency to make a force act on the particles when they reach the gap.
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What is the synchrotron and what advantages did it have over the cyclotron?
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The disadvantage of cyclotrons is that they need a large area because the particles spiral out into large radii. In a synchrotron, varying magnetic field strength is used in order to keep protons in the same radius.
Because the radius of the proton travel remains the same, the extra space saved from the cyclotron model can be used to build more powerful synchrotrons that are able to accelerate protons to even higher velocities and hence increase the maximum energy particles created. |
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Why are colliding beams more useful than protons hitting targets?
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When a proton hits a target, most of the high energy of the proton is transmitted into kinetic energy as the target recoils. On the other hand, Colliding beams simply combine their energy when they collide to form new particles. The excess energy appears as mass after the collision.
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Why is all the energy available in collision of beams?
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Because of the conservation of momentum, the two particles have 0 momentum in total due to their travel in opposite directions. This means that any resulting mass after the collision has no momentum either. This means that all the energy of the protons is put into creating mass.
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What are some detectors?
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The spinthariscope
The cloud chamber The bubble chamber. The spark chamber |
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How are the results of particle acceleration interpreted?
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- The length of the track - the more energy a particle has, the longer its track.
- The thickness - the charge - The curvature - the charge |
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What is an antiparticle?
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A particle matching a regular particle with the opposite charge.
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What is pair production?
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The production of a particle and its antiparticle by 2 gamma rays. Only occurs near other particles.
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What is pair annihilation?
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The transmutation of a particle and its antiparticle into 2 gamma rays.
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What are the three groups of particles?
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Leptons
Mesons Baryons |
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Which ones are hadrons and what does this mean?
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Mesons and baryons because they are influenced by the strong force.
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What are the leptons?
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electrons, positrons, neutrinos and antineutrinos, muons and taus.
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What are the flavours of quarks?
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Up
Down Strange Charmed Bottom Top |
