Topic 4 - Electronics Flashcards
What is electricity?
The movement or build-up of charged particles
What is static electricity?
The accumulation of charged particles
What is electric current?
The flow of charged particles, typically electrons / ions, through a conductor
Conventional current
- flow of positive charge
- flow is from the positive terminal of a power source to the negative
- the direction was established in the early days of electrical theory by scientists who believed that electrical current flowed in this manner
Electron flow
- actual movement of electrons in a circuit
- flow from the negative terminal to positive of a power source
- electrons are negatively charged, movement constitutes the real flow of charge in most circuits
Direct current (DC)
- type of electrical current that flows in one constant direction
- produced by batteries and solar panels
- provides a constant voltage, used to power portable devices and electric vehicles
DC - Drift velocity
- average speed at which free electrons move through a conductor
- electrons drift slowly, electric signal propagates at a significant fraction of the speed of light
- typical drift velocities are in the order of m/s
Alternating current (AC)
- type of electric current where the direction of flow reverses periodically
- the electric grid and transmits alternating current to homes and businesses
- used to power appliances, lightning and machinery
AC
-has a frequency, pertains to how many times the current changes direction per second
- generated by rotating a coil within a magnetic field or vice versa, creates a sinusoidal voltage and current waveform
- frequency depends on the rotational speed of the generator
AC power transmission
- ac power is more suitable for long-distance electricity transmission, can easily be transformed to higher / lower voltages using transformers: helps reduce energy losses
- transformers use electromagnetic induction to transfer electrical energy between wire coils
- AC can also be converted to DC when required
Electric charge
- measured in coulombs (C)
- 1 Coulomb = 6.24150934×1018 electrons
Electric current:
- flow of electric charge
- charge is carried by electrons moving in a wire
- measured in coulombs per second (C/s) = Amps / Amperes (A)
Voltage
- potential difference between two points
- moving 1C of charge across 1 volt of p.d requires 1 joule of work
- measured in joules per coulombs (J/C) = (V)
Basic circuit
- power supply: pushes charge around circuit
- voltmeter: measures p.d in volts (j/c)
- resistor: resists flow of charge
- ammeter: measures flow of current in amperes ( C/s)
- difference pressure cell: makes pressure drop
- pump: pushes liquid around circuit
- long/narrow pump: resists flow of liquid
- flow meter: measures flow of liquid
Ohm’s Law
V = IR
- v: potential difference, volts (V) - driving force
- I: current, amps (A) - flow of charge
- R: electrical resistance (ohms) - resistance
Electrical power
P = IV
- P: power (Watts , J/s)
- V: voltage (volts, J/C)
- I: current (amps, C/s)
Electric components
- Building blocks used to create electronic circuits
Resistors
- restrict flow of electrons in a circuit
- provides a precise amount of resistance
- fundamental to controlling voltage and current within a circuit
Capacitors
- store electrical energy temporarily
- influence the rate of which voltage builds up and drops within the circuit
- crucial in timing and filtering applications
Inductors
- oppose changes in current flow
- store energy in a magnetic field when a current flows through them
- useful in filtering and tuning circuits
Diodes
- only allow current to flow in one direction
- use p-type and n-type semiconducting materials to create a p-n junction
- junction acts as an insulator until sufficient voltage with the correct polarity is applied
Transistors
- can switch or amplify electrical signals
- use p-type and n-type semiconducting materials
- referred to as “solid-state” because they have no moving parts
integrated circuits (ICs)
- compact devices that contain tiny electric components embedded within a single semiconductor chip
- perform a variety of electronic functions, including amplification, signal processing and calculations