magnetic fields

Question 1

what objects are affected by the electromagnetic force?

Answer 1

magnets and magnetic materials

Question 2

What is the exchange particle for electric and magnetic fields?

Answer 2

photon

Question 3

Magnetic field strength is proportional to?

Answer 3

speed of the charge F=B/qv

Question 4

What is magnetic flux measured in?

Answer 4

Weber (Wb)

Question 5

What does magnetic flux show?

Answer 5

the path of a positive charge in the field

Question 6

What does magnetic flux density show?

Answer 6

the strength of the magnetic field

Question 7

What is magnetic flux density measured in?

Answer 7

Teslas (T)

Question 8

What is magnetic flux density in webers?

Answer 8

Wb/m^2

Question 9

What is the magnetic flux density range for calculations?

Answer 9

5 x 10^-3 T is for a fridge magnet
100T is for a white dwarf

Question 10

The principles of electromagnetism

Answer 10

every electrical wire with a current must have a magnetic field

Question 11

What does the magnetic field around a current carrying wire look like?

Answer 11

concentric circles

Question 12

which direction does current move?

Answer 12

conventional current - positive to negative

Question 13

what happens to flux density if you increase current?

Answer 13

flux density increases

Question 14

what happens if you reverse the current?

Answer 14

the polarity of the magnet field reverses

Question 15

What causes a resultant force on the wire?

Answer 15

a difference in magnetic flux density above and below the wire

Question 16

What factors affect the magnetic force?

Answer 16

1) greater flux density = greater flux cut by conductor = greater force
2)greater the length = greater flux cut = greater force
3)greater current = greater flux =greater force

Question 17

What is the equation for the magnetic force?

Answer 17

F = BILsin@

Question 18

How do you measure the length of the conductor?

Answer 18

Only the length of the conductor in the field

Question 19

Define a Tesla?

Answer 19

the magnetic flux density of a wire 1m carrying one amp as a force of 1N is exerted on it in a direction perpendicular to both flux and current

Question 20

Why is the force produced?

Answer 20

due to the interaction of the magnetic fields of the wire with the magnetic field of the magnet

Question 21

If there is a wire experiencing a magnetic force downwards, what happens to the reading on the balance?

Answer 21

it decreases (balance measures reaction force on whatever is carrying the wire)

Question 22

What do you use to vary the current in the experiment?

Answer 22

variable resistor

Question 23

What is the equation for magnetic force on a particle?

Answer 23

Bqv

Question 24

what equation can you use if the particle is deflecting?

Answer 24

mv^2/r (centripetal force)

Question 25

what is the equation for the radius of deflection?

Answer 25

r= mv/Bq

Question 26

What is the relationship between momentum and radius?

Answer 26

as momentum increase, radius of deflection increases r=mv/Bq

Question 27

Describe a cyclotron

Answer 27

-2 semi circular disks (Ds) - there is a uniform magnetic field perpendicular to the planes of the dees - there is a small gap between the dees where an alternating voltage is applied in the gap

Question 28

what if the voltage was not alternating in a cyclotron?

Answer 28

the particle would slow down after leaving the second electrode

Question 29

what does NOT affect the time a particle spends in the dee?

Answer 29

speed t=pim/Bq

Question 30

Derive why velocity does not affect the time a particle spends in the d?

Answer 30

t = 2pi r/v (replace r with r=mv/Bq) t= 2pim/bq

Question 31

compare magnetic flux density and magnetic flux

Answer 31

density: the number of field lines passing through a unit area flux: number of field lines in a region

Question 32

Give an equation of magnetic flux in terms of magnetic flux density for one wire

Answer 32

Flux = B x Acos@

Question 33

What is flux linkage?

Answer 33

the product of the flux and the number of turns on a coil

Question 34

what's the equation for flux linkage?

Answer 34

N x flux =BANcos@

Question 35

What is the unit for flux linkage?

Answer 35

Wb turns

Question 36

What is faradays law of induction?

Answer 36

induced emf is proportional to the rate of change of flux linkage