Current Electricity Flashcards
Electric current
Electrons flowing through a circuit generating electricity
Current electricity
The controlled flow of electrons through a conductor
Electric circuit
A continuous path in which electrons can flow
Source
The resources for electric power (EX. electric cell, three-cell battery, DC power supply, etc.)
Load
The part of an electric circuit that converts electrical energy into other forms of energy (EX. lamp, electric motor, etc.)
Control device
The part of an electric circuit that controls the energy flow from the source to the load (EX. a switch)
Direct current (DC)
A flow of electrons in one direction through an electric circuit
Alternating current (AC)
A flow of electrons that alternates in direction in an electric circuit
Series circuit
A circuit in which the loads are connected end to end so that there is only one path for electrons to flow
Parallel circuit
A circuit in which the loads are connected by branches so that there are two or more paths for electrons to flow
Conductor
A material that lets electrons move easily through it (EX. silver, copper, etc.)
Insulator
A material that does not easily allow the movement of electrons through it (EX. plastic, rubber, etc.)
Current (I)
A measure of the rate of electron flow past a given point in a circuit; measured in amperes (A)
Potential difference (voltage) (v)
The difference in electrical potential energy per unit charge measured at two different points; measured in volts
Resistance (R)
The ability of a material to oppose the flow of electric current; measured in ohms (Ω)
Primary cell
An electric cell that may only be used once
Secondary cell
An electric cell that can be recharged
Watt
The unit of measurement for electrical, one watt is equal to one Joule per second
(W=J/s)
Kilowatt-hour (KW-h):
The SI (metric) unit for measuring electrical energy usage; the used of one kilowatt of power for one hour
Efficiency
Comparison of the energy output of a device with the energy supplied
What do simple electric circuits typically contain
An energy source, a load, conducting wires and sometimes, a switch
Points about electrical energy
- electrical energy is measured in joules (J)
- electrical devices use electrical energy to do work
- work occurs when one form of energy is converted into another form of energy
Examples of sources of electrical energy
- batteries
- electric generating stations
Advantages of hydro-electric dams
- will never run out of this electricity source
- many possible locations for generating stations
- small-scale hydro-electric projects are in good shape
Disadvantages of hydro-electric dams
- dams change the way water flows
- changes ecology of a watershed
- land may become flooded
- disrupts fish migration
- blocks salmon from reaching spawning grounds
- costs are high for both consumers and construction/operation
Review all photos
In iPhoto’s
What is current electricity
Electric charge that is moving (the electrons are flowing from one atom to the other atom)
What is a moving charge called
Electric current
What is an electric circuit
A controlled path through which electric current passes; used to convert electrical energy into other forms of energy
Ammeter
A device used to measure electric current
must be connected in series
Voltmeter
A device used to measure potential difference (voltage)
must be connected in parallel with the load
Ohmmeter
A device used to measure resistance
must be connected in parallel with the load
Factors that affect resistance
- Type of material
- Cross sectional area
- Length
- Temperature
Type of material
The ability of a material to conduct electricity (how freely electrons can move)
Cross sectional area
Thicker wires have less internal resistance (electrons have more room to move)
Length
Longer wires have more resistance (electrons have to travel through more material)
Temperature
When the temperature increases, vibrations increase causing more collisions with electrons and more resistance
Resistor
A device that reduces the flow of electric current
Symbol in photos
Examples of resistors
- lamps with more than one setting
- dimmer switches in the wall
- volume controls on a stereo
Ohm’s law definition
The straight-line relationship between voltage and current
What is ohms law
As the potential difference (v) across a load increases, so does the current
Formula for ohm’s law
R=V/I
Looks in photos
Grass method
Given Required Apply equation Solution Statement
Loads in series
More loads, more resistance, less current
More identical lamps connected in series means less of an electron’s electric potential energy gets converted into heat and light
Loads in series formula
Look in photos
V= V source/# of loads
Loads in parallel
More loads, more paths electrons have to follow
Loads in parallel formula
I Load= I source/# of loads
