Magnetic Fields Flashcards
Which pole is attracted to the other pole?
The north pole is attracted to the south pole
What do flux lines represent?
The direction of force experienced by the North pole of a magnet, by the South Pole.
Where is a magnetic field strongest
Where the flux density is highest (flux lines are closest together)
How is a magnet of double strength represented?
Twice as many flux lines in the same area
What is magnetic flux density?
The number of magnetic flux lines that pass through an area of 1m^2
- measured in Teslas(T)
What is a tesla
The flux density that causes a force of 1N on 1M of wire, carrying a current of 1A, perpendicular to the flux
What is a solenoid?
A current carrying coil of wire that produces a magnetic flux
What is the relationship between PD and flux density?
they are proportional - when in a magnetic field
What is the size of the force acting on a current
F = BIL sin(theta)
B = field strength
I =Current
L = length of wire
What is the force on a charged particle moving in a magnetic field?
F = BQv
B = field strength
Q = charge
v = velocity
What direction does a charged particle move when its at a right angle to flux lines?
It moves in a circles
because the force is perpendicular to the motion and work is force multiplied by distance moved in direction to force. Because of this, no work is done, which means the kinetic energy doesn’t change
How can you relate the equation of F = BQv to other equations?
mv^2/r = BQv
centripetal force = force on charged particle in a magnetic field
What is a cyclotron?
a particle accelerator that accelerates charged particles through a spiral path using a fixed magnetic field and an alternating PD
How does a cyclotron work?
2 semi circles are separated by a small gap and are connected to a high frequency alternating PD. The magnetic field is perpendicular to the semi circles, which causes charged particles to move in a circular path within these. The particles experience a PD when they pass through the gap, and gain energy = Qv. Now they have more energy, they accelerate. This PD alternates direction every time the particles reaches the gap
How do you derive the formula for the time spent in each semi circle of a cyclotron?
mv^2/r = BQv
v = BQr/m
radius is proportional to speed of particle, the radius increases each time the gap is passed.
t = pi*r/v
t = pi*m/(BQ)
