Electrical Principles and Technologies Part Two Flashcards
What are Insulators?
Electrons are tightly bound to the nucleus, allowing little movement. (wood, rubber, air)
What are conductors?
Electrons are free to move to the positive terminal when a voltage source is applied.
How do neon signs work?
Usually gas would be an insulator but when current is applied, the electrons are excited and free themselves from the atoms. Creates a mixture of charged particles which conducts electricity.
What are semi conductors?
At high temps they act like conductors, at low temps they act like insulators. (germanium, silicon, etc)
What are superconductors?
Perfect conductors (no resistance). Some metals act as superconductors at extremely low temperatures.
What is resistance?
Allow current to pass through but provides resistance, limiting the current.
What is a switch?
A device that allows the flow of electrons or when the switch is open there is no flow, because there is a gap.
What is a rheostat?
It is used to change the electron flow gradually. (ex. dimmer switch)
What is the unit of resistance?
The Ohm
What does Ohm’s law state as long as the temperature stays the same.
- the resistance of a conductor stays constant
- the current is directly proportional to the voltage applied
How to calculate voltage, current, or resistance?
V= I*R v= voltage
I= V/R I= current (amp)
R= V/I R= Resistance
Two most common types of resistors?
1) Wire wound: the larger and thinner the wire the higher the resistance
2) Carbon-composite: by varying composition and diameter, different resistances are available.
What do voltmeters do?
They measure voltage differences (voltage drop) in volts.
What do ammeters do?
Measure small currents.
What do multimeters do?
can measure voltage, current, and resistance in a circuit.
Parts of a circuit?
- A source provides energy and supply of electrons for circuit.
- a conductor provides a path for current.
- a switching mechanism controls current flow, turning it on and off or directing it into different parts of the circuit.
- a load converts electrical energy into another form of energy.
What is an open circuit?
The switch is open, the circuit is off.
What is a closed circuit?
The switch is closed, the circuit is on.
What is a series circuit?
- one pathway for current
- entire circuit shuts down if there is a single break
- adding components increases resistance and decreases the current
What is a parallel circuit?
- multiple pathways for current
- components in circuit can have own pathway
- adding resistors decreases total resistance of the circuit
What are microcircuits?
Transistors are used with 3 layers of specially treated silicon with the middle layer receiving a small voltage, allowing it to control the voltage in the outer layers. This allows the transistors to act as switches.
