Magnetism Physics Laycott

Flashcard maker : Jazzlyn Howe
Like poles
repel
Magnet poles ___ be isolated
cannot
If you cut a magnet in half
You get two smaller magnets
If you keep chopping up a magnet, you will eventually reach a minimum size, below which the pieces cease to be magnets.This is called
A Magnetic Domain
__are magnetic at the microscopic level
Permanent Magnets
__are those that can become strongly magnetized, such as iron and nickel
Ferromagnetic materials
Ferromagnetic materials are made up of tiny regions
called domains; the magnetic field in each
domain is
in a single direction
Magnetic data storage
store information as a microscopic pattern of magnetic domains which can be magnetized to write data, and measured to read the data.
The Earth’s Magnetic field
Strength
BEarth = 0.5 x10-4 Tesla
The Earth’s Magnetic field
Generated by
circulating currents in the Earth’s molten iron core
__showed that ALL magnetic fields are due to moving charges
Einstein
Magnetic fields are a consequence of
Special Relativity
Conductor w/ no current
no net charge
right hand grip thumb is
current
rught hand grip pointer is
field
right hanf grip middle is
force
A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force?
to the left
Symbol for Magnetic Field/Units
B/Tesla
This equation defines the magnetic field
F=IlBsin(0)
at right angle F=IlB
A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force?
upwards
A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force?
into the page
If a charged particle is moving perpendicular to a uniform magnetic field, its path will be
a circle.This happens because the magnetic force points at right angles to the particle’s direction of motion.the particle feels a centripetal force.
Atoms are neutral objects whose net charge is zero thus,
they do not experience a magnetic force.
A proton enters a uniform magnetic field that is perpendicular to the proton’s velocity. What happens to the kinetic energy of the proton?
it stays the same. The velocity of the proton changes direction but the magnitude (speed) doesn’t change. Thus the kinetic energy stays the same.
current PRODUCES s B-field, how to
calculate it:
B=u/2pi x I/r u=constant
Parallel currents
attract
antiparallel currents
repel
All Magnetic Fields are due
to electric charges in motion
___ is a long coil of wire. If it is tightly
wrapped, the magnetic field in its interior is almost ___
A solenoid/Uniform
Soleniod formula
B=uIN/l
____:a piece of iron is inserted in the solenoid, the magnetic field greatly_
electromagnets/increases
An electric motor also takes advantage of___, to change electrical energy to mechanical energy.
torque on a current loop
Loudspeakers use the principle that a magnet exerts a force on a current-carrying wire
to convert electrical signals into mechanical vibrations, producing sound.
A magnet moving near a conductor (a wire or a coil of wire) causes an electric current to flow called
induction
A _____consists of two coils,
either interwoven or linked by an iron
core. A changing emf in one induces
an emf in the other.
transformer
Transformer ratios
Vs/Vp=Np/Ns N=number of turns
Transformers work only if__,this is one reason why electricity is transmitted as__
if the current is changing/AC
___will interrupt the current to a circuit that has shorted out in a very short time, before a dangerous current flows, preventing electrocution.
A ground fault circuit interrupter (GFCI)
GFCI:Anti-parallel currents produce opposite magnetic fields, so a short distance away from the wires, there in
NO NET Magnetic Field.If even a tiny current leaks out of the device (say to your wet finger as you reach for a hair
dryer), the incoming and outgoing currents become imbalanced. a second coil opens a switch.
it transforms mechanical energy into electrical energy.
A generator
Generators that use magnets and coils, plus a source of mechanical power are often called
Alternators (the simplest and most efficient
type of generator.)
Alternators produce
alternating current
is induced in each coil in the generator
A sinusoidal emf
The frequency of the AC waveform depends on
how fast the generator rotates
A generator has a coil of wire rotating in a magnetic field. If the rotation rate increases, how is the maximum output voltage of the generator affected?
increases
__has a fixed coil and a magnet
hung on a spring (or vice versa), and records the current induced when the earth shakes.
A seismograph
The magnetic force is __to the
magnetic field direction.
perpendicular
In order to change the magnetic flux through the loop, what would
you have to do?
Since Φ = B A cosθ , changing the
area or tilting the loop (which varies
the projected area) would change
the magnetic flux through the loop
An electron is traveling horizontally toward the north in a uniform magnetic field that is directed vertically downward. In what direction does the magnetic force act on the electron?
east
A charged particle enters into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle’s weight, what type of path will the particle follow?
The charged particle will follow a circular path.
The magnitude of the magnetic field at a certain distance from a long, straight conductor is represented by B. What is the magnitude of the magnetic field at twice the distance from the conductor?
At twice the distance, the magnitude of the field is B/2
Two long parallel wires are placed side by side on a horizontal table. The wires carry equal currents in the same direction.the following statements are true…
The magnetic force between the two wires is attractive. The magnetic field at a point midway between the two wires is zero.
How strong is the magnetic field 2.5cm from one cable?
B = (Uo)I / 2pi*r
What current would the wire carry?
Fb=Fg
ILB=mg
IkB=2 pi (d/2)^2 g (density copper)
the following will produce a magnetic field
The Earth.
An electric current.
A magnet.
A moving electric charge.
When a charged particle moves parallel to the direction of a magnetic field, the particle travels in a
straight line.
As a proton moves through space, it creates
both an electric field and magnetic field.
the following statements about the force on a charged particle due to a magnetic field are all valid
It depends on the strength of the external magnetic field.
It acts at right angles to the direction of the particle’s motion.
It depends on the particle’s velocity.
It depends on the particle’s charge.

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