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An appliance's electrical system can be compared with a home's plumbing system. Electrical current flows along wires in much the same way as water flows through pipes. Both electricity and water enter the home, are distributed through the house, do their “work” and exit. With plumbing, water flows through a pressurized supply system. Electricity current flows along “hot” wires. Current flowing along hot wires is also pressurized. The pressure of electrical current is called voltage. Larger supply pipes have a greater capacity to carry larger amounts of water. In the same way, larger wires can carry more current than small wires. Water is distributed for use by faucets, valves, and showerheads. Electricity is made available through receptacles, switches, and fixtures. Water leaves the home through a drain system that is not pressurized. Similarly, electricity flows back through neutral wires. The current within neutral wires is not pressurized and is said to be at zero voltage.
Circuit: A complete path from positive to negative through which electricity can travel.
Load: Component that converts electricity to heat, light, or motion. All loads restrict the flow of electricity while performing their work.
Conductor: Material through which electricity can flow. It will usually be a copper wire, and sometimes the chassis, or metal frame, on which the components are mounted.
Short: A circuit that offers no resistance to the current flowing through it. A direct short will cause a breaker or fues to blow and possibly start an electrical fire. A direct short is when electrons find an alternate path to a ground source that offers no resistance, such as water or a broken wire contacting the grounded metal cabinet of an appliance.
Shorted Switch: A switch that has fused in the closed position and can offer no resistance to the flow of current through it.
Open Switch: A switch that will not allow current to flow through it.
Closed switch: A switch that will allow current to flow through it.
Continuity: When an electrical circuit is capable of conducting current, it demonstrates electrical continuity. It is also said to be “closed” because the circuit is complete.
1. Power Source
A circuit must have a power source such as electricity supplied by a wall socket, battery, or generator.
Conductors are usually copper or aluminum wire, in some cases it can even be the frame on which the components are mounted.
The load is the components that do all the work, such as a washer motor, heating element, or light bulb.
Controls are devices that control the flow of electricity to the loads. A control is usually some sort of switch that is operated by the user of the appliance, or operated by the appliance itself.
Voltage is the electrical force that moves electrons through a conductor.
Voltage is electrical pressure, also known as EMF (Electro Motive Force) that pushes electrons.
The greater the difference in electrical potential push (difference between positive and negative), the greater the voltage force potential.
A VOLTMETER measures the voltage potential across or parallel to the circuit.
The Voltmeter measures the amount of electrical pressure difference between two points being measured.
Voltage can exist between two points without electron flow.
Voltage is measured in units called VOLTS.
Voltage measurements can use different value prefixes such as millivolt (mV 0.001volts), volt (V), Kilovolt (kV 1,000 volts)
CURRENT is the quantity or flow rate of electrons moving past a point within the circuit in one second. Current flow is also known as amperage, or amps for short. Higher voltage will produce higher current flow, and lower voltage will produce lower current flow.
An AMMETER measures the quantity of current flow. Ammeters are placed in series (inline) to count the electrons passing through it, in much the same way as a water meter counts the gallons of water flowing through it.
Current flow is measured in units called Amperes or AMPS.
Amperage measurements can use different value prefixes, such as microamp (µA 0.000001), milliamp (mA 0.001), and Amp (A 1).
AFFECTS OF CURRENT FLOW
Two common effects of current flow are Heat Generation and Electromagnetism.
When current flows, heat will be generated. The higher the current flow, the greater the heat generated. An example would be a light bulb. If enough current flows across the filament, it will glow white hot and illuminate to produce light.
When current flows, a small magnetic field is created. The higher the current flow, the stronger the magnetic field. An example: Electromagnetism principles are used in alternators, ignition systems, and other electronic devices.
Resistance is the force that reduces or stops the flow of electrons. It opposes voltage.
Higher resistance will decrease the flow of electrons and lower resistance will allow more electrons to flow.
Infinite Resistance: so much resistance that current cannot flow through the circuit ("open circuit.")
Zero Resistance: no resistance and current can flow through the circuit ("closed circuit")
An OHMMETER measures the resistance of an electrical circuit or component. No voltage can be applied while the ohmmeter is connected, or damage to the meter will occur.
Example: Water flows through a garden hose, and someone steps on the hose. The greater the pressure placed on the hose, the greater the hose restriction and the less water flows.
Resistance is measured in units called OHMS.
Resistance measurements can use different value prefixes, such as Kilo ohm (K 1,000) and Megaohms (M 1,000,000).
Various factors can affect the resistance. These include:
- LENGTH of the conductor. The longer the conductor, the higher the resistance.
- DIAMETER of the conductor. The narrower the conductor, the higher the resistance.
- TEMPERATURE of the material. Depending on the material, most will increase resistance as temperature increases.
- PHYSICAL CONDITION (DAMAGE) to the material. Any damage will increase resistance.
- TYPE of MATERIAL used. Various materials have a wide range of resistances.
- click here for a more in depth look at resistance.
There are two basic types of Electricity classifications:
is electricity that is standing still. Voltage potential with NO electron flow.
is electricity that is in motion. Voltage potential WITH electron flow. Two types of Dynamic electricity exist:
ALTERNATING CURRENT (AC)
Electricity with electrons flowing back and forth, negative - positive- negative, is called Alternating Current, or AC. The electrical appliances in your home use AC power.
DIRECT CURRENT (DC)
Electricity with electrons flowing in only one direction is called Direct Current or DC.
DC electrical systems are used in cars.
Electricity can be created by several means: Friction, Heat, Light, Pressure, Chemical Action, or Magnetic Action.
A battery produces electricity through chemical action; an alternator produces electricity through magnetic action.
Friction creates static electricity.
Heat can act upon a device called a thermo couple (used by most pilot driven safety valves) to create DC current.
Light applied to photoelectric (solar panels) materials will produce DC electricity.
Pressure applied to a piezoelectric material will produce DC electricity.
Chemical Action of certain chemicals will create electricity.
This department of defense video shows how a magnetic field can be used to produce an AC current (alternating current)
Basic Electricity PDF
• Electrical wiring
• Alternating Current
• Direct current