Forces on Charged Particles

Question 1

electric fields

Answer 1

imagine a test positive charge
outwards from positive
inwards towards negative

Question 2

what is a force field

Answer 2

a region where an object experiences a force without being touched
eg: gravitational, magnetic, electric

Question 3

uniform fields

Answer 3

closer together=stronger force
further away a particle gets, less strength of field acting on it
field lines in parallel plate equally spaced

Question 4

what does a charged object create?

Answer 4

an electric field

Question 5

what happens when a charged particle moves

Answer 5

it will also produce a magnetic field

Question 6

what will happen if a charged particle is in a magnetic field?

Answer 6

it will experience a force

Question 7

what does each finger represent in the right hand rule?

Answer 7

index - magnetic field
middle - direction of particle
thumb - direction of force

Question 8

left or right for a positively charged particle

Answer 8

left

Question 9

left or right for a negatively charged particle

Answer 9

right

Question 10

what does x mean

Answer 10

into the page

Question 11

what does o mean

Answer 11

out of page

Question 12

how can something accelerate and travel at constant speed?

Answer 12

change in velocity - either magnitude or direction
particle follows curved path, constantly changing direction
eg: roundabout

Question 13

what does it say about the magnetic field if there is no change in velocity of the electron

Answer 13

the magnetic field must be parallel to the motion of the electron

Question 14

what path does electron follow if force is at right angles?

Answer 14

circular path

Question 15

what happens to kinetic energy if direction is changing

Answer 15

velocity is changing but magnitude of velocity stays the same so Ek=1/2mv squared remains the same

Question 16

if a negative charge moves through an electric field from negative to positive, the energy will appear as…

Answer 16

kinetic energy

Question 17

if a positive charge is moved from negative to positive then work has to be done. the energy is stored as…

Answer 17

electric potential energy

Question 18

change in potential energy=

Answer 18

work done

Question 19

work done in electric field equation

Answer 19

W=QV (v=E/Q)

Question 20

once the charge is released…

Answer 20

the electric potential energy is converted into kinetic energy

Question 21

moving charges in electric fields equation

Answer 21

QV=1/2mv squared (QV=Ek)

Question 22

what are particle accelerators?

Answer 22

devices that use electric and magnetic fields to accelerate charged particles to very high speeds for particular purposes

Question 23

example of particle accelerator

Answer 23

cathode ray tubes used in older-style televisions/computer monitors

Question 24

Types of particle accelerators

Answer 24

1. linear accelerator
2. circular accelerators
3. synchrotrons

Question 25

The Large Hadron Collider

Answer 25

27km of tunnels on the France-Switzerland border with massive detectors placed at various points along its route

Question 26

Cathode ray tubes

Answer 26

large glass tubes that contain a particle accelerator

types include: deflection tubes, Maltese cross tubes or Perrin tubes

Question 27

how cathode ray tubes work

Answer 27

an electric field between the cathode and anode causes electrons to be accelerated from one to the other

Question 28

linear accelerators (linacs)

Answer 28

a charged particle is attracted towards a plate in a ‘drift’ tube

the particle passes through one of these tubes and is then accelerated towards the next and so on.

the field between each drift tube must change rapidly so that each new tube attracts the particle leaving the previous tube

kept in centre by series of magnets but in order to increase the energy and velocity of the particle, the accelerator needs to be big. (eg: longest is Stanford Linear Accelerator in California)

Question 29

circular accelerators (cyclotron)

Answer 29

work by using a series of magnets to keep the particles in a circular orbit. this allows high-frequency voltage supply to accelerate the particles

can be smaller and therefore cheaper

comprises two D-shaped sections with a small gap and a very high potential difference between them

a charged particle is accelerated across the gap then bent inside one of the dees until it is in the opposite direction. It accelerates across the gap again and process is repeated until particle has correct energy

as particle becomes faster, path radius increases and it moves out towards the edge of the dees. at very high speeds, relativistic effects interfere with the efficient operation of the cyclotron and it can become difficult to adapt the fields in line with the particle.

Question 30

Synchrotrons

Answer 30

synchrotron radiation is emitted under the conditions mentioned before and this can lead to energy loss in particle physics experiments

we can build the synchrotron such that the radiation is produced at certain frequencies for scientific/medical purposes

specific type of circular accelerator where magnetic and electromagnetic fields have been adapted to produce a very energetic and narrow ring of charged particles at very high energies

many synchrotrons produce high energy x-rays for spectroscopy where structure of atoms are investigated

Question 31

examples of synchrotrons

Answer 31

The Large Hadron Collider and the Fermilab in the USA (massive and extremely expensive)