Electromagnetic induction - magnetic fields Flashcards
Which direction would the arrows be going near a south pole?
Towards
Which direction would the arrows be going near a north pole?
Away
Which direction does a dot show in a magnetic field diagram?
Coming out of the page
Which direction does a cross show?
Going into the page
Magnetic fields cause what?
Magnetic fields cause a moving charge to feel a force.
What do moving charges produce?
Moving charges produce a magnetic field around itself.
Explain the right hand grip rule.
- Thumb: showing the direction of CONVENTIONAL current.
- Fingers: showing the direction of the magnetic field
How do you increase the strength of the magnetic field around a current carrying wire? (3 points)
- Increase the current
- Increases number of charges flowing
- Stronger magnetic field
How does a coil of insulated wire with current produce a magnetic field?
- Current flows through the wire
- Using the right hand rule the magnetic field goes through the middle of the coil
An example of a permanent magnet and a temporary magnet?
- Perm; bar magnet
- Temp; solenoid
Magnetic Flux Density is…
… is the density of magnetic field lines in a given area (strength of a magnetic field).
Letter and unit for Magnetic Flux Density
B, Tesla (T)
Flux is…
… is a scalar measure of the magnetic field interacting with a surface area
Letter and unit of Flux
Φ, Weber (Wb)
Flux linkage is…
… is the flux interacting with multiple loops in a coil, rather than just one wire/surface
Letter and unit for Flux Linkage
NΦ (N = number of loops), Weber-turns (Wb-turns)
What is the equation used to link flux and magnetic flux density?
Φ = BA sinθ
Fleming’s left hand rule
Follow FBI
- Thumb: direction of force
- Index: magnetic field direction
- Middle: direction of CONVENTIONAL current
If the field lines and direction of current are parallel, is there a resultant force?
No, because sinθ would be sin(0) which is equal to 0.
Derivation of r = p / BQ
- F = Bqv
- F = mv^2 / r
- Bqv = mv^2 / r (make them equal)
- Bq = mv / r (divide by v)
- Bq = p / r (p = mv)
- p / Bq = r (rearrange)
If the velocity decreased of a moving charge through a magnetic field, what would happen to it’s turn radius?
- F = Bqv sinθ
- if v decreased and the centripetal acceleration didn’t change
- as F = Bqv sinθ is lower, F of F = mv^2 / r is lower
- r must have decreased so
- tighter turn radius of charge
Derive F = BIl from F = Bqv
- F = Bqv
- F = BQv (I = Q/t)
- F = BItv (v = s/t)
- F = BIs (s = distance = length)
- F = BIl
Equation for flux (fie)
flux = BA sin (theta)
