| what is charge measured in? | coulombs |
| what is an electric field | a region of space around a charge where another charge will experience force |
| what do electric fields exist around | any object that is charged |
| on an electric field diagram, what do the arrows represent | the direction a positive charge would move if placed in that field |
| what does the relative spacing on an electric field diagram show? | the strength of the field
the closer the lines to each other, the stronger the electric field |
| what does an electric field diagram look like with two opposite charges | ... |
| what does an electric field diagram look like with two oppositely charged parallel plates | ... |
| what will happen if charged particles pass through a uniform electric field? | they will move as a force is being exerted on them |
| is energy required to move a charge in an electric field? | yes
work is done in moving a charge in an electric field |
| what will happen to the potential energy of a charge if it is moved in the opposite direction to the electric field | it will increase since the energy required to move it against the field is stored |
| give a formula that relates work done to electrical potential energy | W=QV
W is work down in Joules
Q is electric charge in coulombs
V is potential difference (voltage) in volts |
| what is voltage | the energy given to each coulomb of charge in a circuit |
| what is one volt the same as | 1 joule per coulombif one joule of work is done in moving one coulomb of charge between any two points in an electric field, the potential difference between the two points is one volt |
| what happens to kinetic energy if a charge moves in the direction of the electric field | it will increase due to the work done on it by the electric field |
| what formula should you use to calculate kinetic energy of a charged particle released from rest | QV=1/2mv^2 |
| what formula should you use to calculate kinetic energy of a charged particle that is not starting from rest | work done=change in kinetic energy |
| how are magnetic fields visualised/drawn | drawn as field lines running from north to south |
| what does a magnetic field exist around | moving charges eg. current carrying wire has a magnetic field around it |
| what happens when a moving charge passes through an external magentic field | it experiences a force
the direction of which depends on the type of charge, and the direction of the magnetic field |
| how can you predict the direction of force acting on a charge moving through a magnetic field | left hand slap rule |
| what must the conditions be in order for a particle to be deflected by a magnetic field | particle must be: charged moving not travelling in the same direction as the magnetic field |
| what are particle accelerators | devices that use electric and magnetic fields to accelerate charged particles to very high speeds for particular purposes |
| what is a linear accelerator (linacs) | a type of particle accelerator in which a charged particle is attracted towards a plate in a drift tube. |
| how do charged particles move through linear accelerators? | a charged particle is attracted towards a plate in a drift tube it passes through one of these tubes and is then accelerated towards the next it passes through this tube and is accelerated towards the next and so on |
| how are charged particles attracted to each drift tube in linear accelerators? | the electric field between each drift tube must change rapidly so that each new tube attracts the particle leaving the previous tube |
| how are charged particles kept in the centre of linear accelerators? | a series of magnets is used, creating a magnetic field |
| what must a linear accelerator be in order to increase the energy and velocity of charged particles? | long the longer the particle accelerator, the more the particle will be accelerated, meaning more kinetic energy |
| why do drift tubes gradually increase in length in linacs | as speed of the particles increases they travel further in the same time |
| what is a cyclotron | a circular particle accelerator which works by using a series of magnets to keep the particles in a circular orbit |
| what are charged particles accelerated by in cyclotrons? | high frequency voltage supply |
| what is the structure of a cyclotron? | a cyclotron consists of two D shaped sections (dees) with a small gap with a high potential difference between them |
| how are charged particles accelerated in cyclotrons? | a charged particle is accelerated across the gap between the dees and bent inside one of the dees until it is in the opposite direction.
it accelerates across the gap again and the process is repeated until the particle is at the correct energy.
At this point it is released. |
| why is alternating voltage supply used in a cyclotron | to ensure the electric field is always in the correct direction |
| what is a synchrotron | a specific type of circular accelerator where the magnetic and electromagnetic fields have been adapted to produce a very energetic and narrow ring of charged particles at very high energies |
| what are many synchrotrons used for | to produce radiation for experiments and medical applications |
| what can synchrotrons produce | highly energetic photons across a range of frequencies high energy X rays for spectroscopy (where the structure of atoms can be investigated) |
| how do synchrotrons work? | particles are accelerated to high energies and focused together in order to collide
huge detectors are then used to detect and analyse the remnants of two protons |
| why do particle accelerators need to be evacuated | so that collisions or interactions with other particles can be avoided |
| what is final kinetic energy of a charged particle that is already moving | initial kinetic energy + work done |
| what is maximum kinetic energy of an electron ejected from the surface of a metal | energy of the photon incident on the plate minus the work function of the metal |
