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Module 6 - Chapter 23 - Magnetic fields I - Coggle Diagram
Module 6 - Chapter 23 - Magnetic fields I
Magentic field
Field surronding a permanent magent/ current carrying conductor in which magnetic object experiences a force
Magentic field patterns
Arrow is direction a free north pole would move (north to south)
Equally spaced parallle lines show uniform field
Close lines mean a strong field
Field is strongest at poles
Electromagnetism
Magentic field is created around a current carrying wire
Any charged particle that moves creates a magentic field around it ( eg: electrons moving in the wire)
Magnetic field of bar magnet is caused by electrons whizzing around the iron nuclei
Iron atoms act as tiny magnetis, aligned in the same direction
Current-carrying conductors
Field lines for a current-carrying wire are concentric circles centered on wire and perpendicular to it
Right hand grip rule shows direction of coventional current
Magnetic fied outside solenoid is similar to bar magnet. At centre of the core, it's uniform
Flemings left hand rule
When conductor is placed in an external magnetic field, two fields interact like permanent magents - equal and opposite force experienced
Direction of force experienced by current-carrying conductor placed perpendicular to the external magnetic field can be determined used F.LH.R
First finger gived direction of external magnetic field
Second finger gives direction of conventional current
Thumb givs direction of motion(force) of the wire
Magnetic flux density
Force is max when wire is perpendicular and 0 when parallel
B = magnetic flux density - strength of the field measured in Tesla
B is 1T when a wire carrying a current of 1A placed perpendicular to the magnetic field experiences force force of 1N per metre of its length
B is a vector quantity
Determining B
Magnets are placed on a top-pan balance
Magnetic field is almost uniform
Stiff copper wire is held perpendicular to the magnetic field between the two poles
Length is measured using ruler
Section of wire is connected in series with an ammeter and power supply usinf crocodile clips
Balance is zeroed when there is no current in the wire
Wither a current I, the wire experiences a vertical upward force, so magnets experience an equal downard force shown by change in mass reading
F = mg where g is acceleration of free fall
Circular tracks
Chagred particle moving in a magnetic field experiences a force, which can be shown using an electorn deflection tube
Electrons change durection, and force on each electron is always perpendicular to its velocity
Speed remains unchanged because the force has no component in direction of motion
Once out of the field, electrons keep moving in a straight line
Current carrying wire in uniform magneitc field epxeriences a force as each electron epxeriences a tiny force
Force on each particle =
Going around
Particle moving at right angles to uniform magentic field can be described using circular motion
Faster more massive particles travel in bigger circles
Particles in stronger magnetic fields and greater charge move in smaller circles
Velocity selector
Device that uses both electric and magnetic fields to select charged particles of specific velocity
Consists of two parallel horizontal plates connected to power supply which product uniform electric field between plates
Uniform magneitc field is produced perpendicular to plates
Charged particles travel at different speeds to be sorted through a narrow slit
Field deflect particles in opposite direction, only particles with a specific speed will these cancel so they travel in a straight line and emergy from the second narrow slit
mass spectrometers
Measure mass and relative concentrations of atoms and molecules
Accelerated and ionised atoms pass through velocity selector and emergy with the same speed
Particles enter a uniform magnetic field and each ion is deflected a different amount depending on mass
