M field Flashcards
definition of 1 tesla
flux density that exert a force of 1N on 1m of wire carrying 1 A(amp),B=F/IL
condition for resultant force acting on a charged particle moving in the magnetic field
field line is perpendicular to velocity
path of the charge entering the field
circular
what is the work done when charge entering the M field
zero
acceleration of the charge when entering the field
towards the centre of circle (F=mv^2/r)
speed of the charged particle in the field
constant
what is cyclotron
charged particle accelerator that contains semi-circular electrodes “Dees”, strong uniform magnetic field and alternating electric field
where is the source of protons in cyclotron
centre of the circle
briefly explain how happens when the particle enter the dee
-source of charged particle at the centre
-magnetic field applied perpendicular to the path
-magnetic force acting perpendicular to the path and the field
-moving in circular path in the Dees
when particle crossing the gap between the Dees
-electric field is applied
-alternating voltage and field accelerates the particle due to electric force
-moving in higher speed and larger radius in the follow path in the Dees
role of magnetic field in cyclotron
To supply the centripetal force needed to keep the particles moving in circular motion
role of electric field
To accelerate the particles between the Dees
formula of the radius of the protons path
r=mv/BQ
formula of time taken for the proton to travel through one dee(semi-circle)
t=m(pi)/BQ
what factors affect the final velocity
radius of the dee and magnetic field strength
does time taken for a particle moving around the Dees depend on speed of the charge
no
what can we say about the time period of the AC voltage
constant as particle moving in constant speed in the Dees
In mass spectrometer what conditions will the ions pass through the E and M fields in a straight line
forces by the two fields acting in opposite direction and are equal (EQ=BQv)
describe the process of electromagnetic induction
inducing emf(p.d.) in a conductor when there is a relative motion between the magnetic field and a charge
define flux
total amount of magnetic field lines(magnetic flux)in a given area, flux=BA
define flux linkage
amount of magnetic flux in all the loops added together
when is the flux/flux linkage at its min and max
max when the plane of area is perpendicular to the field lines(cut the field lines)
min when the plane is parallel the field lines (does not cut the field lines)
formula of flux linkage
flux linkage=N(/BA)fluxcos (theta), where theta is the angle between the axis of the coil and the flux
factors that increase the emf induced in a coil
-increasing the magnetic field strength
-increasing speed of motion of the magnet
-adding more turns
factors that decrease the emf in a wire
-decrease the length of wire
-decrease the strength of the magnet
- reduce the speed of motion of the magnet
what does Faradays law suggest
that the magnitude of induced emf is proportional to the rate of change in magnetic flux linkage
what does Lenz’s law suggest
the direction of emf induced will oppose the change that causing the induced emf
formula of induced emf in a coil rotating uniformly in a magnetic field
ε=BANωsin ωt
equation for induced emf for a conductor of 1 turn
ε=Blv
what is time base
how many seconds in each division represent
what does it mean when a vertical straight line shown on the oscilloscope
time base is turned off and only voltage is shown
what does it mean when a horizontal straight line shown on the oscilloscope
dc supply as voltage remains constant
shape of graph for ac current/voltage
sinusoidal
how can p.d. cross the two coils in a transformer
-alternating current and voltage in the primary coil
-this causes change in magnetic field therefore change in magnetic flux linkage inside the iron core
- emf is induced in the secondary coil
what is the role of iron core
-increase the strength of magnetic field
-channel the magnetic field through the secondary coil
what happen when secondary coil has more turns
increased voltage output
describe eddy current
-eddy current is induced in the core
-as magnetic field is changing
-inducing an emf is in the core
-this produces a field that oppose the field in the core and reduces its strength
causes of insufficiencies in transformers
-eddy current
-hysteresis–>iron ions rotate, causes friction
-wire power loss P=I^2R
ways to reduce insufficiencies
-use soft iron to reduce hysteresis
-use thicker wire to reduce resistance
-laminating the core
