electricity - electric charges and currents Flashcards
name some models of atoms in history
plum pudding model
Rutherford bohr model
charge cloud model
rutherford model
what is an atom made up of
protons (positive charge)
neutrons (no charge)
electrons (negative charge)
what do you need for an electric current to pass round a circuit?
- a complete circuit
- source of potential difference (battery)
what is electric current
rate of flow of charge in wire
what is the current due to?
passage of charged particles, called charge carriers
_____ field in the ____ caused by _____ source _____ all _____ to move
electric field in wire caused by voltage source induces all electrons to move
what is the convention of the direction of current
from positive terminal to negative
symbol for charge
Q
what are electrons in a circuit
Electrons are the charge carriers that flow in an electrical circuit – from the negative to positive terminals.
unit for charge
coulombs C
charge of proton (and electron)
1.6 x 10^19 C
what is conservation of charge
no net electric charge can be created or destroyed
what is electricity?
movement of charge around a circuit - electric current
what is electric current
movement of negative charges (electrons) in a circuit
rate of flow of charge
unit for current
ampere A
symbol for current
I
equation for current when there is a charge and time
Q = IT
one amp of current is due to _______________________
a flow of charge of 1 couloumb per second
what are 3 categories a material can be classified in electrical terms
conductors, insulators, semi-conductors
what is an insulator?
each electron is attached to an atom and cant mov away.
when voltage is applied across insulator - no current passes through
as no electrons can move through
what is a metallic conductor
most electrons are attached to atoms but some are delocalised (free to move)
delocalised electrons are charge carriers
when voltage is applied across metal, these conduction electrons are attracted to positive terminal
what is a semi conductor
number of charge carriers increases with an increase in temperature
resistance of a semi conductor decreases as temperature is raised
what makes a good conductor
allows electrons to move throw them easily
what makes a good insulator
does not allow electrons to move easily
what does a battery have potential to do?
potential to transfer energy
what happens when a battery is in a circuit?
each electron passing through a circuit component does work to pass through the component and therefore transfers some/all of its energy
work done by an electron is equal to….
The work done by an electron is equal to its loss of energy.
what is work done per unit charge defined as?
potential difference
what is potential difference?
Potential difference is defined as the work done (or energy transfer) per unit charge.
what is the unit of pd
volt
equation for p.d
V = W / Q
w - work done
q - charge
what is the emf
The emf of a source of electricity is defined as the electrical energy produced per unit charge passing through the source.
unit of emf
volt
what is internal resistance
The resistance to the flow of charge within a source. Internal resistance results in energy being dissipated within the source.
equation for work done by charge carriers
work done = IVt
current
pd
change in time
equation for electrical power
P = IV
unit - watt
what is one volt equal to
one volt is equal to one watt per amp
