Physics Test Review Flashcards
electrically neutral
describes an object that has equal amounts of positive and negative charges
charging by friction
process of charging materials by rubbing them together
insulator
A material in which electrical charges cannot move easily. (ex. glass, wood, styrofoam, plastic)
conductor
a material in which electrical charges can move easily (ex. copper, iron, gold, silver)
how to test whether something is a conductor or insulator
conductivity meter. if material is insulator, no movement or light, if material is conductor, light or action
static electricity
the buildup of negative charges in one place
law of electric charge
opposites attract, likes repel
electroscopes
used to detect electric charge (ex. Pith Ball, Metal Leaf)
charging by conduction (contact)
Two differently charged objects come in contact
Electrons flow from the more negative object to the more positive
Objects will not necessarily be neutral but have the same amount of electrons afterwards
charging by conduction: using a negatively charged object
Before contact, ebonite rod was negative and electroscope was neutral. You can tell as the leaves hung down. After contact, electrons from ebonite rod moved into electroscope making it negative. The leaves repel because they’re both positive
what happens when we rub a charged object on a metal conductor?
metals allow electrons to move around freely, causing them to be unable to build up in one place or cause static electricity
pith ball
-plant material hanging from string
-if a charged object is brough near it will move
grounding
-way of removing excess charge
-transfer electrons from small object into large object such as the earth
-earth is large so it spreads out and becomes neutralized
-for a positive object electrons travel back into object until neutralized
electric discharge
-quick transfer of electrons from one place to another
-happens when 2 objects with charge imbalances are brought together but do not touch
-electrons move from more negative to more positive
what do we experience from electrical discharge
-crack or pop
-air temp increase
-sparks between objects
lighting
-caused between ground and clouds
-electrons transferred between water droplets moving past each other. ex of charging by friction
-negative molecules collect at cloud bottoms
lightning rod
-gives electrons safe path to the ground
-made of metal
-protects buildings
current electricity
- refers to electrons that flow through a conductor in a controlled way, steady flow
- there is a steady flow of electrons through a conductor
types of batteries (electrical cells)
- primary cells: single use batteries (lithium, alkaline)
- secondary cells: can be recharged by reversing the flow of electrons (lead-acid, NiMH, lithium)
- fuel cells: chemicals are continuously pumped into the cell, resulting in a longer battery life (hydrogen)
types of current electricity
- direct: can only flow in one direction (ex. devices that use a battery)
- alternating: can flow in multiple directions (ex. generating stations flow in an alternating current)
what is needed for electrons to flow in a current?
conductors because they hold electrons loosely
what makes electrons flow through a conductor?
batteries
where do applinces without batteries get electrons from?
outlets which are connected to power generating stations
what are electrical charge measure in?
joules
circuit
continuous loop consisting of an energy source, conducting wires, one or more loads, and a switch
basic circuit requirements
a load, source of electricity, electrical conductor, and control device
what type of electric cell is suitable for a flashlight or smoke detector?
primary cells as they have a low discharge rate than other types of batteries which is suitable for appliances like flashlights and smoke detectors as they are not often used
they are also quite compact and energy dense
current
flow of charge (amount of charge passing through a point per second)
what is current measured with? and whats the symbols
ammeter A and I
potential difference
difference in potential energy per coulomb of charge at one circuit point compared to another
what is potential difference measured with
voltmeter
resistance
something that slows the flow of electrons in a circuit (the loads)
result of the conversion of energy to other forms as the current passes through a load
what is resistance measured with?
ohmeter
give 5 examples of current electricity generators
hydro-electric, biomass, geo-thermal, tidal, nuclear, solar, wind