Electrics Flashcards
Conductor
A material that has many free electrons and allows current to flow
Insulator
A material that resists flow of current
Charge
A net surplus or deficiency of electrons in an object
Static Electricity
An object which has gained electrons and cannot lose them has a static negative charge
If the object has a net deficiency of electrons it has a static positive charge
Voltage
The force or pressure that allows electrons to flow
EMF
Current
The rate of flow of electrons
Resistance
Opposition to current
Ohm’s Law
Voltage = current x resistance
More voltage means more current flow
More resistance means less current flow
Electric Power
The rate of work
Power = Voltage x Current
Circuits
A closed path through which current can flow
Direct Current (DC)
Current flow in one direction
Produced by batteries or converted by a rectifier from AC
Alternating Current (AC)
Current whose flow reverses at regular intervals
Produced by alternators or converted by an inverter from DC
Measured by mean voltage or cycles per second
Reverse Current Relay
Limits the minimum generator voltage, to protect the battery
Power source with greater voltage will drive the electrics
Takes the generator out of the circuit when its output falls below that of the battery
Sources of Electrical Power
The battery
The alternator
The Alternator
Generates electricity mechanically by spinning an electromagnet near a coil
Once the engine is started, the alternator charges the battery and powers electrical systems
Has a slightly higher voltage output to ensure the alternator powers the system instead of the battery
Produces AC
Usually 28 volt
The Battery
Can store electricity Rated according to voltage and capacity Can supply power for a finite time Contains electrolyte Usually 24 volt
Venting
Battery must be ventilated to prevent a build up of hydrogen and oxygen produced by the lead-acid batteries
Voltage Regulator
Maintains the correct voltage output form the generator
Overvoltage Relay
Prevents excess voltage from going to the bus bar in the case that the voltage regulator fails
It isolates the alternator and the battery supplies the power
Bus Bar
A distribution point to which all the electrical services are attached
Circuit Breakers and Fuses
Isolates each circuit if a surge of current threatens to damage it
Tolerate a number of amps before popping
Only reset once
Battery Master Switch
Connects the battery to the electrical system and drives the circuit for the alternators magnetic field
The Centre Zero Ammeter
Located in the battery circuit and indicates the current flowing to or from the battery
Should normally show a slight positive charge as the battery is charges
If the battery is discharging the needle is deflected to the minus side
The Left Zero Ammeter
Located in the alternator circuit and indicates the output of the alternator
Normally deflected to the right
A zero indication signals an alternator failure
External Power Receptacle
Provision for an external power source to be plugged in
Conserves battery power and is connected by a relay requiring a small current from the battery
Gauge of the Wire
The thickness of the wire and is determined by the current
Alternator Fault
Warning light will turn on
Recycle the switch, holding for 1-2 seconds, if it faults again turn the alternator switch off
Can supply all the electrics and will load shed non-essentials if necessary
Capacitor
Stores electricity for a moment when a switch is turned off
Eg. the magnetos
Transformer
Increase or reduce electricity (volts)
Step-up or step-down
