Chapter 22 Flashcards
what is a current
it is the motion of a charge through a conductor
when we connect a charged parallel plate capacitor to a conducting wire, what happens to the net charge od the plates and why
the plates are discharged as the charges flow through the wire in a current
what are charge carriers
charges that move in a current
what are conduction electrons
they are electrons that move around in a metal and create a current
why can an insulator not have a current
no, the elecrons do not flow easily
describe the motion of electrons in a current of a metal
an electric field within the metal exerts a force on the electrons that causes them to accelerate.
these electrons collide into eachother, and kinetic energy is lost as thermal energy which makes the metal warmer
what direction do electrons move in an electric field?
they move opposite of the electric field
when there is a potential difference what happens to the electric field and the current in a wire
the potential difference causes an electric field that points from high potential to low. This drives a current that flows from high to low
if a conductor has a current, why is it not at equilibrium
the charges are in motion
what is the law of conersevation of current
the current is the same at all points in a current-carrying wire.
on either side of a bulb, what is the relationship of the current going into the bulb vs out
it is the same and it is conserved
what direction does current flow?
it flows in the direction of positive charge
What is another way to describe current
it is the rate (C/s) at which charges move through a wire
what is the unit of current
it is 1 ampere= 1A= 1 coulomb per second
what is a junction? what happens to the current of a wire when a junction is present
a junction is where a wire spilts or merges into one. The sum of the current in is the same as the sum of the current out
what do batteries do for.a current
they keep the charges in motion through energy conversions
how does a charge escalator work in a battery
due to chemical reactions, the charges are moved from the low-potential negative terminal and “lifted” to the high-potential positive terminal
what does the charge escalator do for a current
it sustains the current by continuously providing a renewed supply of charges at the positive terminal
What happens in a battery when the charge reaches the positive terminal?
it flows downhill from high potential to low potential and the potential energy is converted to kinetic energy as the charge flows downhill back into the battery in a complete circuit
what is emf or ε
the potential difference created in a battery
what happens to the potential difference when we connect a battery in a series
the potential difference is the sum of the individual batteries differences
what in a battery creates a potential difference
the removal of a charge from the negative to the positive terminal
what is a consequence of a battery’s potential difference
the current
what is resistance
it is how hard it is to push charges through a wire
the potential difference between the two ends of a wire connected to a battery are equal to what
they are equal to the potential differences in the batteries terminals
what happens to the current when you add a battery to in a series?
the difference in potential increases so the current increases
what happens to the current when you use a short and thick wire on a battery
the current is stronger
what happens to the current when you use a long, thin wire
the current is smaller
what are the three factors that affect current
the dimensions of the wire, the potential difference in the batteries, the material of the wire
what are the units of resistance
ohm
what is resistivity
it is an inherent property of a material
materials with a low resistivity are good at what?
conducting
materials with a high resistivity are good at what
insulating, they are poor conductors
whats the difference between resistivity and resistance
resistivity is a property of a material whereas resistance depends on the specific geometry of a wire
why is ohm’s law not a law of nature
not all objects have a constant resistance
what are objects that adhere to ohm’s law called
they are called ohmic
what are objects that do not obey ohms law lcalled
nonohmic
what types of objects does ohm’s law apply to
resistive devices like wires or lightbulb filaments
what objects does ohm’s law not apply to
batteries or capacitors
what is a voltage drop
it is a decrease in potential across a resistor as we go from high potential to low potential in a current
the electric field inside of a resistor is
uniform
what happens to the chemical energy of a battery as it moves through a resistor
it is converted into electric potential energy, kinetic energy, and then it is transformed into thermal energy in the resistor and raises it’s tempertaure
the rate at which a battery supplies energy is equal to what
the rate at which a resistor dissipates energy
