M6, C3 Electromagnetism Flashcards
Which way do field lines go on a magnetic field
from north to south
the closer the field lines on a magnetic field, the _______ the field
stronger
how could you determine the direction of the magnetic field around a current-carrying wire
When a current flows through a wire, a magnetic field is created around it.
Use the right-hand rule.
Point your thumb in the direction of the current through the wire.
Your curled fingers will then show the direction of the field.
what can magnetic fields be caused by
moving charges
or
permanent magnets
draw the magnetic field pattern of a flat coil
page 147 of year 2 textbook
draw the magnetic field pattern of a long solenoid
page 147 of year 2 textbook
what is Fleming’s left-hand rule
You can use your left hand to find the direction of the current, the direction of the external magnetic field or the direction of the force on the wire.
Point your thumb up, middle finger to the right and index finger forward.
First finger = direction of the uniform magnetic field
Second finger = direction of the conventional current
Thumb = direction of the force (motion)
define magnetic flux density
the force on one metre of wire carrying a current of one amp at right angles to the magnetic field
is magnetic flux density a scalar or vector quantity
vector
what are the units of magnetic flux density
teslas (T)
One tesla is equal to one newton per amp per metre
What equation can you use to calculate the force on a current-carrying wire which is perpendicular to a magnetic field
F = BIL
B = magnetic flux density I = current through wire L = length of the wire F = force on the current-carrying wire
what happens to the magnetic field when you put a current-carrying wire in between 2 magnets?
page 147 of the year 2 textbook
The 2 fields are added together making a resultant field.
Lines closer together show where the magnetic field is stronger.
The size of the force depends on the component of the magnetic field that is perpendicular to the current. Use Fleming’s left-hand rule.
What does the equation F = BILsinθ mean
For a wire that is at an angle to the field, the force is given by this equation.
F = force on a current-carrying wire B = magnetic flux density I = current through the wire L = length of the wire θ = angle between wire and field
Outline an experiment you can do to measure the magnetic flux density
Use F=BIL
page 151 of year 2 textbook shows diagram
a current-carrying wire is placed between two magnets. the mass is measured, it will change because a force will act upwards or downwards
An electrons travels perpendicular to a magnetic field of flux density 0.15T. Calculate the acceleration of the electron given its speed is 5X10^6 ms^-1.
F = BQv = Bev
= 0.15 X 1.6X10^-19 X 5X10^6
= 1.2X10-13 N
F = ma
a = 1.2X10^-13 / 9.11X10^-31
= 1.3X10^17 ms^-2
Charged particles travelling perpendicular to a magnetic field travel in a __________.
Circular path
Derive an equation you can use to calculate the radius of circular path of charged particles.
F = mv^2 / r F = BQv
mv^2 /r = BQv
r = mv / BQ
What happens to the radius of the circular path, if the mass or velocity of the particles increases
increases
what happens to the radius of the circular path, if the strength of the magnetic field or charge on the particle increases
decreases
what are velocity selectors used for
to separate out charged particles of a certain velocity from a stream of accelerated charged particles moving at a range of speeds
how do velocity selectors work
they apply both a magnetic and electric field at the same time perpendicular to each other, while a stream of particles is fired perpendicularly to both fields at a device with a narrow gap called a collimator
opposing forces are experienced from the magnetic and electric fields
magnetic field tries to deflect the particles upwards F=BQv
electric field tries to deflect the particles downwards F=EQ
particles won’t deflect if the forces are balanced
BQv = EQ
Bv = E
So only particles with velocity v = E/B will travel in a straight line to pass through the gap in the collimator
what is magnetic flux
The total magnetic flux passing through an area, perpendicular to a magnetic field is defined as:
Φ = BA
You can think of flux as the number of field lines in an area.