Flashcards in Charged particles in a magnetic field Deck (11):

1

What happens when a charged particle is moving in a magnetic field?

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- force is exerted
- this is why a current-carrying wire experiences a force in a magnetic field
- electric current is the flow of -vely charged electrons

- electric current is the flow of -vely charged electrons

2

Derive the equation F = BQv from F = BIL

use data sheet

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- electric current, I = Q / t
- chargged particle which move a distance l in time t has a velocity, v = l / t
- so l = vt
- therefore F = BIL = BQvt / t = BQv

3

Describe the deflection of a charged particle in a magnetic field?

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- deflected in a circular path

4

Why does the particle move with circular motion?

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- FLH rule says that the force n a moving charge in a magnetic field is always perpendicular ot its direction
- mathematically, that is a condition for circular motion

5

How do you use FLH rule for charged particles?

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- use your second finger (normally current) as the direction of motion for a positive charge
- if particle carries a -ve charge, point second finger in opposite direction to its motion

6

why is force due to magnetic field independant of mass but the centripetal acceleration does?

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- F = BQv
- no mass in equation

- Newtons 2nd law
- particles acceleration will be a = v
^{2} / r
- combining with newtons second law F = mv
^{2} / r
- this is force on a particle in circular orbit

- no mass in equation

- particles acceleration will be a = v
^{2}/ r - combining with newtons second law F = mv
^{2}/ r- this is force on a particle in circular orbit

7

Rearrange the equaiton to give r

use data sheet

what happens if the raidus increases or decreases?

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- radius increase
- particle deflected less
- m or v increase

- radius decreases
- particle deflected more
- B increase or Q increase

- particle deflected less
- m or v increase

- particle deflected more
- B increase or Q increase

8

What are cyclotron?

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- make use of circular delflection
- particle accelerators

9

What are the uses of cyclotrons?

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- medicine
- radioactive tracers
- high=energy beams of radioation for use in radiotherapy

10

What is a cyclotrons made up from~?>

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- two hollow semicircular electrode with a uniform magnetic field applied perpendicular to the plane of the electrons and an alternating potenttial difference between electrodes

11

How does a cyclotron work?