Forces and Fields/Magnetism Flashcards
Electrostatics
the study of charges not in motion
Law of Conservation of Charge
the net amount of electric charge produced in any process is zero. you cannot create or destroy charges
what is an ion
an atom that has lost or gained electrons
conductivity
a way of describing how easily charges move through a material
insulators
charges do not move easily. (most materials besides metals (plastic, glass, rubber))
conductors
charges move easily, they are free moving. most metals
separation of charge (polarization)
movement of electrons in an neutral object where one side becomes positive and the other side becomes negative.
charging by friction
rubbing two materials together, causing electrons to transfer from one material to the other. some materials hold electrons better than others. results in oppositely charged objects
charging by induction
when a charged object comes close enough to induce a charge (no contact), causing a redistribution/separation of charges. results in oppositely charged objects
charging by conduction
when a charged object comes in contact with another and electrons transfer from one to the other. charges are shared this results in identically charged objects
grounding
the process of connecting a charged object to the earth which will cause the grounded object to neutralize in terms of charge.
electroscope
an instrument used to detect the presence and nature of a charge. the more the leaves diverge, the greater the charge
Coulomb’s Law
describes the electrostatic force between two charged objects in relation to the distance between them. Fe = (kq1q2) / r^2
What did Coulomb use to study the relationship between distance and charge?
a torsion balance apparatus
Fields
arc spheres of influence and cause an ‘action at a distance’. number of field lines indicate strength
vector fields
have specific directions as well as magnitude
Electric Fields
radiate away from positive charge and towards negative charge.
test charge
the mathematically perfect charge that could be brought near another charge (source charge) to measure the source charge’s electric field.
potential difference
the work required to move a charge between two points in an electric field
current
the flow rate of an electric charge
What was Millikan’s experiment
he used the the electric field created by two parallel plates to determine the charge of an electron (the oil drop experiment)
how did Millikan’s oil drop experiment work
he dropped oil droplets between two charged plates. the positive ones would accelerate down, towards the negative plate, the negative ones would fall enough for Fe=Fg
can causing by induction cause permanent charge changes?
yes. if an something neutral is grounded and a positive rod is brought near it, the electrons in the object and more electrons from the ground will move towards the positive rod. when the ground is removed, there are more electrons than there where before.
who developed the idea of field lines?
Michael Faraday
how can work be done in an electrical system
pull opposite charges apart or push like charges together
what does a cathode ray tube do
it uses electric fields to accelerate electrons (aka electron gun)
cathode is connected to
negative terminal
anode in connected to
positive terminal
which metals experience noticeable net force in a magnetic field?
iron, copper, nickel
what are magnetic fields caused by
moving charges
what causes magnets
electrons spinning, causing magnetic fields
what are domains
small magnets inside magnets.
which direction do magnetic field lines point?
towards south and away form north
what did Hans Christian Oersted discover?
electrons moving in the form of current also produce electric fields
First Hand Rule (for straight conductors)
determines direction of magnetic field. Thumb - charge direction, Curled Fingers = magnetic field direction
what does looping a current-carrying wire do
it increases the magnetic field
solenoid
a coil of wire
the shape of the magnetic field of a solenoid is
similar to that of a bar magnet
more loops in a solenoid
increases field strength
Second Hand Rule (for coils)
determines direction of magnetic field caused by a current-carrying coil. Curled Fingers = direction of current flow, Thumb = direction of North magnetic pole
Third Hand Rule (for moving charges in magnetic field)
determines the direction of the force acting on a charged particle as it moves through an external magnetic field. Thumb = direction of charge motion, Fingers = magnetic field direction, Palm = direction of force on particle.
What happens to neutral objects in electric or magnetic fields?
they are not deflected
moving charges are known as
electric current
what direction do electrons flow
from negative to positive
if the conductor is levitated in the magnetic field
Fm = Fg
What kind of force does magnetic force act like
centripetal force (center-seeking) (Fm=Fc)
what is a mass spectrometer
a device that determines the charge to mass ratio of ions
Generator effect (Induction)
a wire that is forced to move through a magnetic field produces a current. the current produced it’s own magnetic field that opposes the original magnetic field.
Galvanometer
device that measures current and it’s direction
Three ways to induce a current
- Move a conductor near a magnet
- Move a magnet near a conductor
- change the strength of the magnetic field
Lenz’s Law
the direction of an induced current will cause a magnetic field that opposes the charge in the external field that is causing the induced current. uses conservation of energy.
Motor effect
current carrying wire in a magnetic field will experience a force causing the wire to turn
How do you tell which direction electric field lines are in?
the direction a positive charge would move (towards negative and away from positive)
what is the net electric field?
the sum of all the individual fields
magnetic fields are produced by
moving charges
where does a compass needle point on a wire
it is deflected perpendicular to the current carrying wire. it shows the direction of the magnetic field
the direction of the current flow affects the
direction of the magnetic field
are electric and magnetic positive and negative the same phenomena
no. positive and negative charges are NOT attracted to or repelled from north and south poles
