Physics Chapter 17 Test
Terms in this set (72)
electric potential energy
Results from interaction of two objects' charge
The sum of the kinetic energy and all forms of potential energy
ME = KE + sigma (E)PE
total or all
When is work done electrically?
Work is done if an electric charge is moved because of the electric field of another object.
uniform electric field
Has the same value and same direction at all points.
Ex: 2 charged parallel - plates
formula for electric potential energy (PE)
PE = -qEd
Electrical Potential Energy = -(charge x electric field strength x displacement)
Similarities between electric potential energy & gravity
Electric field strength does work on a charge by moving it in the direction of the electric field strength. Earths gravity does work on a mass by always moving it towards Earth.
electric potential (v)
the work that must be performed against electric forces to move a charge from a reference point divided by the charge.
electric potential (v)
v = PE/q
v = w/q
potential difference (delta V)
The work that must be performed to move a charge between the two points in question, divided by the charge.
potential difference (delta V)
delta v = - PE electric/ q
delta v = w/q
delta v = Va-Vb
A device that stores energy. A battery provides a constant potential difference between two locations (terminals) in a battery.
What does it mean when it says a battery is 1.5 V alkaline battery?
The potential difference that two terminals is 1.5 V.
A device that is used to store electrical potential energy. It has many uses, including tuning the frequency of radio receivers, eliminating sparking in automobile ignition systems, and storing energy in electronic flash units.
Charged energy can be reclaimed when needed and is energized by connecting to a battery.
Parallel - plate capacitor
consists of two parallel metal petals
the ability of a conductor to store energy in the form of electrically separated charges
formula for capactiance
c = q/delta (v) OR net charge/potential difference
What does capacitance depend on?
Size & Shape of capacitor.
Capacitance increases with size.
An insulating material used to fill the space in a parallel - plate capacitor.
Ex: air, rubber, glass, & waved paper
Increase the capacitance by reducing the charge on the plates
How to discharge a capacitor?
Connecting them to a material that conducts will discharge the capacitor. This is similar to grounding.
Uses for capacitors
1. flashes in cameras
2. computer keyboards or press keys
The rate which electrical charges pass through a given area.
The rate of electric charge.
Uses for electrical currents?
1. Power lights
4. Air conditions
5. vehicle engines
7. human body
Direction of current
Opposite the direction of the movement of negative charge
Formula for Current
I = q/t
positive & negative charges in motion
the flow of positive charge
The direction is from positive terminal to negative terminal .Electrons move in the opposite diection
a solute that dissolves in water to form a solution that conducts electric current.
velocity with which the electrons move in a conductor
the opposition to the motion of charge through a conductor
formula for resistance
R = delta v/ I
The resistance is constant over a wide range of applied potential differences.
The ratio of the potential difference to the current is always constant for a given resistor.
Materials that function according to Ohm's Law
Have a constant resistance over a wide range of potential difference. .
Ex: most metals
Materials that do no function according to Ohm's Law
Semi - conducting device that is non - ohmic used to control the direction of current
What 4 factors determine Resistance
Length - resistance increases with length
Area - resistance decreases with area (wider = less resistance & narrower = more resistance)
structure of atoms making up a material
Relationship between resistance and temp
Resistance increases with temp
George Simon Ohm
1789 - 1854
Examles of Resistors
Wiring in walls & electric devices are resistors
Fact about charges
charges do not move at the speed of light
9 types of solutions
3 states of matter (solid, liquid, and gas) x 3 states of matter (solid, liquid, and gas)
Facts about Solutions & Solvents
salt & water - most common solution
solvent - water
solute - salt
Usually the liquid part of a solution
Usually the solid part of a solution
Relationship between Current & resistance
Uses for resistors
1. Used to control the amount of current in a conductor
2. Could change potential difference to control curren
Amount of Shock the human body feels
<..01 amps: slight shock
>.15 amps: fatal
Humans body when wet & dry
Dry = 500,000 ohms
Uses for the Galvanic Skin Response Test
Stress tests & lie decetors
Resistance decreases & perspiration increases
A special type of resistor that has a fixed contact on one end and an adjustable sliding contact that allows the use r to tap off different potential differences.
Uses for potentiometers
1. joys stick on video games
2. dimmer switch to control outputs of light fixtures
3. volume controls on stereos
Materials that produce no heating or reduction in the current when conducting.
Zero resistance below a certain temperature.
Copper, Silver, and Gold are not superconductors
Remarkable feature or a superconductors
Once a current is established in them, the current continues for years even if the potential difference is removed.
Floating magnet in air over a superconductor
Uses for superconductors
2. microwave devices
What is needed for a current to be maintained?
Potential difference must be maintained across the terminals
Converts chemical energy to electric potential energy .
Stores energy in the form of chemical energy and releases the chemical energy until it is gone. When the energy is gone the batter will need to be replaced. Chemical reaction
Convert mechanical energy into electrical energy. Supply energy to operate your appliances. Generators supply energy to your home with a potential difference over 120V.
Ex: hydroelectric power plants
Two types of current
Direct & Alternating
charges move in one directions
Negative charges move from lower & higher electric potential.
Terminals constantly change sign from (+) to (-)
Charges move back and fourth
In the US the current oscillates 60 times per second (frequency is 60 Hz)
The rate at which charge carriers do work.
The rate at which charge carriers convert electrical potential energy to nonelectric energy
Formula for electric poower
P = w/t
P = (I)(delta v)
The power rating of a light bulb
Amount of heat given off
The conversion of electrical energy to internal energy in a resistant material called Joule heating
Referred to as a IR^2 loss
Kilowatt - Hour
Unit for electrical energy
How do power companies minimize energy loss
Decrease the current of the resistance
Power companies transfer energy at high potential difference to minimize the loss of energy.