Electricity
General term for the variety of phenomena resulting from the presence and flow of electric current
Volts
Amperes (amps)
Ohms
3 ways
... [Show More] Electricity is measured
Volts
Measure the difference of potential between 2 points
Amperes (amps)
Measure the number of electrons that move past a specific point in 1 second
(i.e. electrical currents)
Ohms
Measure resistance, including anything that could limit the flow of electrons
Current
Electrical ___ occurs when electrons move from one place to another.
Conductors
(e.g. copper, silver, water)
A substance, body, or device that conducts electricity; allows the electrons to move freely.
Insulators
(e.g. rubber, wood)
A material of such low conductivity that does not easily allow the flow of electrical current to pass through it; discourages electrical current
Watt
This measures power, the rate at which electrical energy is consumed or transformed into another type of energy, such as light or heat
Power
The rate at which electrical energy is consumed or transformed into another type of energy, such as light or heat
Watt-hour
This is the amount of energy used in 1 hour at a rate of 1 watt.
Kilowatt-hour
The amount of energy used in 1 hour at a rate of 1,000 watts(i.e.1-kilowatt)
True
True or False
Most electricity is measured in kilowatt-hours
Wattage x Time (expressed in hours)
To find watt-hours multiply ___ by ___.
10 kilowatt-hours
How many kilowatt-hours is enough energy to run a 10,000-watt speaker system for 1 hour?
2 hours
10 kilowatt-hours is enough energy to run a 5,000-watt air conditioner for how long?
10 hours
10 kilowatt-hours is enough energy to run a 1,000-watt waffle iron for how long?
Circuit
The path of an electrical current
Open
When there is literally an open space in the circuit that prohibits current from flowing
Short
When the open space of a circuit has been closed to allow current to flow
Voltage
The difference of the pressure between 2 points in a circuit
(sometimes called voltage drop or difference of potential)
True
True or False
To see what the voltage is anywhere in a circuit, you have to compare the voltage at that point to ground
Ground
(e.g. base of a lamp, chassis of a car)
Any part of a circuit (or other object that has electricity running through it) that measures 0 volts
Voltmeter or multimeter
Measures voltage in a circuit
Voltmeter
An instrument used for measuring electrical potential difference between two points in an electric circuit (i.e. voltage)
A voltmeter has 2 leads. To measure voltage, you place one lead somewhere in the circuit and one lead at another location in the circuit. The voltmeter tells you what the voltage is between those 2 points.
How to use a voltmeter:
Cell
A storage compartment for electricity in a battery that has a specific voltage.
True
True or False
You can figure out the number of cells a battery has by dividing the voltage of the battery by the volts.
Electrical current
The flow (rate of flow) of electrons in a conductor
coulombs (C), which measure charge.
Current flow can be expressed in terms of ___.
Coulomb
The amount of electricity provided by a current of 1 ampere flowing for 1 second.
True
True or False
If 1 coulomb (about 6,241,500,000,000,000,000 electrons) flows past a specified point in 1 second, that's a flow rate of 1 ampere (amp, abbreviated A).
Ammeters
Measure the flow of current through a circuit
True
True or False
Typically current is tiny, so small that it's measured in milliamperes; 1 milliampere is one-thousandth of an ampere.
Circuit breaker
A device that automatically interrupts the electrical current.
True or False
True or False
Sometimes a circuit must be opened in order to add or remove resistance. In other words, the flow of electricity must be interrupted in order to physically change the resistance.
Rheostat
A device which can vary the resistance without opening the circuit - the electrical device can continue to work even as the resistance is altered
A dimmer switch on a light; you increase the amount of resistance to dim the light and decrease the resistance to brighten the light
Example of a rheostat
Ohms (Ω)
The SI unit of electrical resistance; measures the amount of resistance that interferes with the flow
Ohmmeter
Device that measures the amount of resistance that interferes with the flow
The amount of voltage (measured in volts)
The resistance to the current (measured in ohms)
The amount of current (measured in amps)
The 3 influences that are present when current flows through a wire
The current in a circuit is directly proportional to the applied voltage and inversely proportional to the circuit resistance.
What is Ohm's law
I
Abbreviation for current
E
Abbreviation for voltage
R
Abbreviation for resistance
Current (amperes) = Voltage(volts)/Resistance(ohms)
OR
I = E / R
Formula to solve for Current
(Ohm's law)
Voltage = Current x Resistance
OR
E=IR
Formula to solve for Voltage
(Ohm's law)
Resistance = Voltage/Current
OR
R = E / I
Formula to solve for Resistance
(Ohm's law)
Watts
Unit of power in the International System of Units (SI)
750 watts
How many watts are to 1 horsepower
True or False
One kilowatt represents 1,000 watts
By multiplying the number of kilowatts (kW) required by the number of hours of use.
(e.g. if you use a 40-watt light bulb 5 hours a day, you've used 200 watt-hours, or 0.2 killowatt-hours of electrical energy)
How are kilowatt-hours determined?
Least
Electricity follows the path of ___ resistance.
Conventional Current
The vacancies left by electrical particles "moving" from the positive (+) terminal to the negative (-) terminal of a battery.
(in regards to electrical flow of current)
True
True or False
The military teaches current flow based on the flow of the electrons, and electrons, no matter how you look at it, flow from the negative terminal to the positive terminal
Short circuit
This occurs when any wire accidentally crosses over another wire, causing the electricity to bypass the rest of the circuit and not follow the intended path
Chemical Effect
Heat Effect
Magnetic Effect
Physiological Effect
4 effects produced by current and some of their commercial applications
Chemical Effect
Current produces this effect when it passes through a chemical compound and breaks that compound up.
(Also called Electrolytic Decomposition, this phenomenon is used in Electroplating)
Electroplating
A process used to cover objects with a very thin coating of metal.
(chemical effect)
Heat Effect
Conducting electricity causes wires to become heated. Heat develops because the current must overcome the resistance of the wire. This heat energy can be quite obvious or hardly noticeable to touch, depending on the size of the wire and the amount of current
Magnetic Effect
When a wire is introduced into a magnetic field, electricity flows through the wire and creates a magnetic field that repels a magnet. This effect is used to create energy through Electromagnetic Induction. If the wire is wrapped around an iron core and a current is sent through the wire, the iron become magnetized.
Electromagnetic Induction
The production of electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, etc.
Physiological Effect
Current produces this effect when it passes through your bicep (or any other muscle) and causes the muscle to contract. This effect is used in medicine.
Direct Current (DC)
Current that only and always flows in one direction
Alternating Current (AC)
Current that constantly changes direction in a regular patter
AC
Most electricity comes in the form of __.
Alternating Current
Higher voltages are easier to obtain with ___ current.
Frequency
The number of times a current completes 2 alternations of direction per second
Hertz (Hz)
The unit of measurement for frequency
True
True or False
One hertz (Hz) equals one complete cycle per second. In other words, the current makes two complete alternations of direction.
60 Hz
The Alternating Current (AC) in your house probably completes 60 alternating cycles per second. Therefore, the AC in your house has a frequency of ___ Hz.
1000 Hertz (Hz)
1 kilohertz (kHz) = ___ Hz.
1 million Hertz (Hz)
1 megahertz (MHz) = ___ Hz.
1 billion Hertz (Hz)
1 gigahertz (GHz) = ___ Hz.
Capacitive reactance (capacitance)
Inductive reactance (inductance)
2 properties of alternating currents that impede the flow of current
Capacitive reactance (capacitance)
The storage of energy that occurs in a nonconductor. This property resists any change in voltage in a circuit.
Inductive reactance (inductance)
The property that causes an electromotive force (another way of saying voltage) to be induced in a circuit.
Impedance = Electromotive force / Current
Formula for Impedance
Capacitors and Inductors
Devices used in circuits to provide the type of reactance needed.
Microfarad (μF)
Capacitors are rated in ___.
Millihenries (mH)
Inductors are rated in ___.
Rectification
The process of making certain electronic circuits change alternating current to direct current.
(i.e. changes incoming AC to DC)
Rectifiers
The circuits that perform rectification
Semiconductor Diodes
Found in rectifiers; a component made of a material with conductivity somewhere between that of a conductor and an insulator
Diodes
These conduct electricity in only one direction.
Inductors and Capacitors
Rectification often requires ___ and ___.
Cooler
Variable
Rectification helps appliances run at ___ temperatures and allows them to run at ___ speeds.
Direct
Devices typically need ___ current to run properly.
Semiconductor
An object that conducts electricity poorly at low temperatures.
Transistor
A semiconductor that controls the flow of electricity in a circuit. Usually made of germanium or silicon.
This electrical device can amplify a signal.
True
True or False
Transistors are small, require little power, and last a long time
Emitter
Base
Collector
3 terminals a transistor contains
Emitter
The voltage output
(transistor)
Base
This acts like a gate, and the voltage at the base controls the flow of current through the transistor (and therefore the voltage)
Collector
The voltage input
(transistor)
Block diagrams
Used to show the various combined circuits that form a complex system
Wires
Used to pass current from one part of the component to another
Joined wires
Wires that are connected to each other and are indicated by a dark circle in diagrams
Unjoined wires
Wires that are not connected; in circuit diagrams, it is necessary to draw wires crossing even though they aren't connected, this is indicated by a hump symbol
Cell
This supplies electrical current.
Battery
Has 2 or more cells. The large terminal is positive
DC Power Supply
This provides direct current; direct current always flows in 1 direction
AC Power Supply
This provides alternating current; alternating current constantly changes direction at a specific frequency
Fuse
A safety device that blows (melts) if the current flowing through it exceeds a specified value
Transformer
Consists of 2 coils of wire linked by an iron core. These are used to step up (increase) and step down (decrease) AC voltages.
No electrical connection exists between the coils. Energy is transferred between the coils by the magnetic field in the core.
Ground
A connection to the earth
Transducer
A device that converts energy from one form to another
Lighting lamp
Indicator lamp
Motor
Heater
Bells & Buzzers
Michrophone
Earphones & Speakers
Examples of Transducers
Lighting lamp
Converts electrical energy to light.
e.g. light bulb, automobile headlight
Indicator lamp
Converts electrical energy to light for such uses as a warning light on a car's dashboard
Motor
Converts electrical energy to kinetic energy (motion)
Heater
Converts electrical energy to heat
Bells and Buzzers
Convert electrical energy to sound
Microphone
Converts sound to electrical energy
Earphones ans speakers
Convert electrical energy to sound
Inductor
A coil of wire hat creates a magnetic field when current passes through it
Push
Push-to-break
On/off
Two-way
Dual on/off
Relay
Types of switches
Push switch
A switch that allows current to flow only when the button is pressed
e.g. doorbell
Push-to-break switch
With this switch, the circuit is normally closed (the device is on), and the circuit is open (device is off) only when the button is pressed
On/off switch
This switch allows current to flow only when it's in the closed (on) position
Two-way switch
This switch directs the flow of current to one of two routes, according to its position [Show Less]