79 terms

Honors Physics Chapter 17 & 18

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electric potential energy
Potential energy associated with the interaction of charges
mechanical energy
Electric potential energy is a form of
no friction or resistance
Mechanical energy is conserved as long as there is
work
Whenever a charge is moved by another charge's electric field force,____ is done
point charges
no PE for
work done
no change in PE, no
electric potential energy
When a charge is moved in a uniform electric field, the change in location relates to a change in
d
is the displacement from reference point
uniform
point charges are not____ because their field weakens at a distance
increase; decrease
The negative sign means that the PE will ____ when the charge is negative and ______ when the charge is positive
perpendicular
No work is done when a charge is moved _____ to an electric field, and the PEelectric remains constant
Electric potential
is the potential energy associated with a charge in an electric field
Potential difference
is the change in electric potential
equation for potential difference
∆V = ∆PEelectric/q
volt (V)
Unit for potential difference is the
Electron volt
a unit of energy, energy 1 electron gains when moved through a potential difference of 1V.
Battery
energy storage unit that maintains a constant potential difference between two locations called terminals
positive----negative
Negative charges inside the battery move from the ___ terminal to the ____
Capacitor
device used to store electric potential energy
energized or charged
When the plates are charged, the capacitor is said to be
potential difference
The plates become charged by connecting them to a source of
Capacitance
is the ratio of the charge to the potential difference of the plates
Unit = farad (F), which is one coulomb/volt
unit for capacitance
ε
is the permittivity of the material,
εo
is the permittivity in a vacuum, which is 8.85x10-12 C2/(Nm2)
material
Changing the____ between the plates of a capacitor will change how much charge it can hold
dielectric
Capacitors made with a _____ between the plates hold more charge - this book assumes vacuum between plates
connected to a material that conducts
Once a capacitor is charged it will remain so until
zero
When discharged, the charges move between the plates until the potential difference is
PE
A charged capacitor stores
transfer of energy
Work done to move the charge is a measure of the
Electric Current
Movement of electric charge
Luigi Galvani
discovered that animals conduct electricity - frog legs twitched when conducting electrical experiments near the frog
Current
is the rate of charge transfer
Unit = ampere (A or amps), one coulomb per second
unit for current
Positive charge movement
Conventional current =
charge carrier
Current motion is actually made up of positive, negative or movement of both - called
Drift velocity =
net velocity of the charge carriers, very small (~25mm/s)
Electrons
in the conductor move along a zig-zag due to their vibrations - causes collisions and energy transfer
slowly
Electrons move ____ through a conductor in the opposite direction from the electric field - however E reaches the electrons at nearly c
resistance
Opposition of the motion of charge through a conductor
Unit: ohm (Ω)
unit for resistance
constant
Resistance is____ over a range of potential differences
less resistance
Greater area =
greater resistance
Longer material =
higher resistance
Higher temperature =
Ohms law
V = IR
ohmic materials
Ohm's law only applies to materials that have constant resistance - called
Resistors
control the amount of current in a conductor
Saltwater and perspiration
lower the body's resistance
Potentiometer -
a type of resistor that allows the user to change the potential difference across a conductor - used on volume control knobs, dimmer light switch, video game controllers
high---low
Free electrons in a conductor move from areas of ___ electric potential to areas of ___ electric potential
constant
Potential difference maintains ____ in a circuit
Direct Current (DC) -
electrons move in one direction, from low electric potential to high electric potential (remember conventional current is flow of positive charge) - conventional current moves from positive terminal to negative terminal
Alternating Current (AC) -
terminals causing potential difference are constantly changing sign, causes charges to just vibrate back and forth rather than flow
Electric Power -
rate of energy conversion
Unit: Watt (W), one joule per second
unit for electric power
kilowatt-hours.
Power companies measure energy usage in
W/s, not kWh
SI unit for electrical energy is
I
variable for current
A
variable for ampere
R
variable for resistance
Ω
variable for ohm
V
variable for potential difference
V
variable for volt
E
variable for electrical energy
J
variable for joule
Series Circuit
-one path
Series Circuit
-constant I
Series Circuit
-sum up V
Parallel Circuit
-2 or more paths
Parallel Circuit
-constant V
Parallel Circuit
-sum up I
electromotive force
EMF
volts
unit for EMF
Series Circuit
-Req> any R of a device
Parallel Circuit
-Req< any components resistance
Series Circuit
-Req= Ra+Rb+Rc....
Parallel Circuit
Req=(1/Ra +1/Rb...)^-1
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