Unit 4: Electricity Flashcards
What is static electricity?
Stationary electricity
Atoms are neutral, (Same # of protons and electrons)
What is Charge Seperation
When charged objects are brought near neutral objects. May cause neutral object to become attracted to charged object
What is electrical Discharge
When a built up charge is attracted to another object and jumps to it. Usually felt as a shock
what is the Van De Graaff Generators
- builds static electricity
How it works - rubber belt rubs on metal
- Transfers charge to sphere where it builds up
What is Current electricity
- steady flow of charged particles
- keeps flowing until source runs out or it cut off
- Conduction occurs through wires in contact
What are free electrons
- electrons separated from out shell
- carry current of electricity in wires
what are the conditions for an electric current
- energy source
- complete path for circuit
What is a circuit
- paths that control the flow of electricity
- typically use solid metal
Includes - conductor, energy source, load
What is a conductor
- rapid flow of electrons in material
Ex. Metalic - copper
Non-metallic - carbon, graphite, water solutions of salt, acids, alkalis
What are insulators
Material resists flow of electrons/ doesn’t allow electrons to flow easily (also called resistors)
Ex. wood, rubber, fabric, Tungsten, Nichrome
What are Amperes
The rate at which an electrical current flow is measured
- Named after French physicist, mathematician, philosopher Andre-Marie Ampere
What devices can e used to measure current
Galvanometer - weak currents
Ammeter - strong currents
What is Voltage
- Electrical energy carried by charged particles
- How much energy each particle charged particle has
- Higher voltage = higher potential energy
- “Potential difference”
how do you measure Voltage
- Volts
- Alessandro Volta, Italian physicist
- Voltmeter
how do you measure Voltage
- Volts
- Alessandro Volta, Italian physicist
- Voltmeter
What is more deadly, Voltage or Current
Current
What are Fuses
Thin metal that melts with too much current
Must be replaced
What are Circuit breakers
- wire that triggers spring mechanism that turns off switch when too hot
- can be reset
What are electrochemical cells
- cells that use chemical reactions to create electricity
- irreversible reaction
What are Dry Cells
- cans full of chemicals that produce electrons
- Chemicals that react are in a paste
- Sealed with asphalt
- made in zinc container also functions as negative pole
- Cell works as long as the paste is moist
What are cell terminals
- cells have two terminals, pos and neg
- electrons flow from neg (zinc) to pos (carbon)
What are wet cells
- use liquid electrolyte (acid) instead of a paste
- cheaper than wet cells, but wear out faster
ex. car batteries
What are the parts of the a wet cell
- effective electrolyte
- two electrodes (one pos and one neg)
- Wires connecting terminals
What is electrochemistry
electrolysis - using electricity to separate useful elements
electroplating - using electricity to coat cheaper metals with expensive metals
What are superconductors
- almost perfect conductors
- almost no resistance electron flow
- discovered by dutch physicist Heike Kamerlingh Onnes in 1911
How are resistors used in appliances
- resistors limit the amount of current
Ex. toasters use high resistance wire to convert the electricity into light and heat
what is resistance
a measure of how difficult it is for electrons to flow through a substance
The more resistance a substance has, the more the substance gains energy from each electron that passes through it
Solutions can also be resistors
- more charged particles = low resistance
- Fewer charged particles = high resistance
What types of resistors are there
- wire round - made of heat resistant alloy wrapped around an insulating core (longer and thinner = high resistance)
- carbon-composition - made of carbon mixed with other materials
What tools are used to measure voltage and amperes
Voltmeters - measuring small voltages (millivoltmeters)
Ammeters - measure current
Galvanometers - measure small currents
Multimeters - measure voltage, current and resistance is a circuit
What are the main parts of a circuit drawing
- Power source
- Conductor
- Load
- Switching mechanism
What is the difference between a parallel and series circuit
Parallel - two or more paths, if one load malfunctions the others, there is still a path from pos to neg
Series - all the loads are in a row, one path for electricity, more loads = dimmer light
What are combination circuits
- has a combination of series and parallel paths
- parallel section is part of a series circuit
What is energy
the ability to do work
What types of energy are there
Chemical – released when chemicals react
Mechanical – energy an object has because of motion or the ability to move
Electrical – energy of charged particles
Thermal – total kinetic energy of particles in a substance
What is the law of conservation of energy
“Energy is neither created nor destroyed, it just changes form”
What is the law of conservation of energy
“Energy is neither created nor destroyed, it just changes form”
What is a thermocouple
- a device that converts thermal energy to electrical energy
- consists of two different metals that conduct heat at different rates
What is are electromagnets
Permanent Magnets - always magnetized, (bar magnets, horseshoe magnets)
Electromagnets - only magnetized when there’s a current (Scrap metal cranes)
What are the parts of an electric motor
- Armature or rotor (electromagnet)
- Commutator
- Brushes
- Axle
- Field magnet
- Power supply
How does a Motor work
- uses magnets to create motion
- magnet poles attract and repel
- The attracting and repelling forces create rotational motion
What are the two types of magnets in a motor
Electromagnet - armature/rotor
Field magnet /permanent magnet
What are the two different types of currents
AC - alternating current, flows back and forth 60 times per sec
DC - direct current, only flows in one dirrection
What is electromagnetic induction
moving a coil of wire through a magnetic field generate a steady supply of electricity
What is power
- the rate at which a device converts energy from one form to another
- the unit is watts
- 1 watt = one joule/second
What is energy
- The ability to do work
- measured in joules
What lowers the efficiency of a machine
- Input energy is often converted to “waste” energy such as heat
- In devices that convert electricity to mechanical energy, friction is responsible for creating a lot of waste energy.
How can you increase efficiency
- better bearings
- use lubricants
- improve insulation
