current electricity Flashcards
what is electricity
flow of charges through a conductor
when does a current flow
when charges flow from one point to another
what is a conductor made up of
metal atoms which have negatively charged electrons that can move when attracted or repelled.
what is a conductor made up of
metal atoms which have negatively charged electrons that can move when attracted or repelled.
what are electrons attracted and repelled to in simple circuit
repelled by negative terminal of battery and attracted to positive terminal of battery if there is a path that runs between 2 terminals, resulting in current in path
how does current flow
from positive to negative
conventional current
convention used rather than tracking electron flow
flow of positive charge from positive terminal of battery through circuit to negative terminal of battery
not correct -created when structure of atom was unknown
circuit
path for charges to flow
(closed circuit)
cant open in open- incomplete
short circuit
direct path from positive to negative terminal
current takes path of least resistance
bad- cause batteries to drain quickly and overheat
current
(I)
rate of flow of charge
no. of coulombs of charge that flow past a point in a circuit every second
measured in Amperes (A) using ammeter connected in series
ammeters
allow charges to flow through them in order to measure quantity of charge that passes a point each second
doesn’t use any energy or obstruct flow
how is energy supplied to charges and circuit
by battery (provides electrical potential energy)
charges carry energy to circuit - changed into other forms by components in circuit (lightbulb,motor)
energy ‘used up’
charged not ‘used up’ - just carry energy through circuit
potential difference
(V)
work done per unit positive charge
messured in volts (V) using voltmeter connected in parallel
measured across component in circuit that uses up energy
comparison of energy carried per unit charge at 2 diff points in circuit-difference
provides push/force on charges allowing them to move through circuit
how does battery have potential difference across ends
because supplies energy (ability to do work) to each unit of charge (Q- measured in Coulumbs-C) that passes through it
potential difference provides push/force on charges allowing them to move through circuit
potential difference of battery also called voltage pf battery
voltmeter
compares 2 points and finds potential difference between them
— potential energy supplied per unit charge
no charges flow through voltmeter
resistors
anything in circuit that slows down flow of charges
electrical appliances
protect other components by restricting amount of current flowing
regulate potential difference across components, allowing them to function efficiently
resistance
materials opposition to flow of electric current
examples of resistors
lightbulbs, heaters, motors, electronic appliances
simple electronics device that only there to change rate of flow and decrease current
opposite of conductor
insulator
relationship between resistance and current
more resistors added
more current decreases
high currents— low resistance
high resistance— low currents
if resistance too high
energy lost
if resistance in high voltage transmission lines too high- heat up and much energy (thermal energy) lost to surroundings
if resistance too low
if resistance in element of geyser or electric kettle too low, won’t heat up
when charges move through a resistor
collide with other charges and nuclei of substance of which resistor is made
during collision- kinetic energy transferred to particles (in the way) and resistor heats up
4 factors of resistance of conductor
length- longer the conductor, greater the resistance
thickness/cross sectional area- greater cross sectional area, smaller the resistance
temperature - hotter the conductor, greater the resistance
conductor material- some materials have greater resistance to electric current
gold,silver,copper - good conductors
tungsten,nichrome- less effective
resistance formula
resistance = voltage over current
R= V/I
resistors in series relationship and formula
increase total resistance of circuit decrease total current in circuit
more resistors connected in series, more resistance in circuit
Rseries = R1 + R2 (however many)
relationship between current in circuit and the total resistance in the series circuit
inversely proportionate - more resistors, more difficult for current to flow
current in series circuit
constant through out
potential difference in series circuit
splits between resistors in connection in proportion to their resistance
Vtotal= V1 + V2 (however many)
cell
an electrical power supply
variable resistor (rheostat)
A type of resistor that can be adjusted
to give a range of resistances
ohms law
current through a conductor is directly proportional to the potential difference across the conductor at constant temperature
resistance in parallel circuit
the more resistors, the less resistance
- more pathways, more current can flow
current in parallel
splits between branches/resistors
resistor w higher resistance- lower current
series circuit
components connected one after each other- 1 path
1 path for current to flow
-current constant throughout
-current slows—> low current
resistance splits Rtotal=R1+R2+R3
more resistors = more resistance
potential difference splits Vtotal=V1+V2
as resistance in increases, current decreases
total voltage of series circuit equal to sum of voltage of all resistors in circuit
-current circuit
parallel circuit
all positive terminals connected,all negative terminals connected
-many paths
-more pathways for current to flow
-higher current
current splits in inverse proportion to total resistance
Itotal=Itop branch +Ibottom branch
potential difference constant Vtotal=V1=V2=V3
more resistors- less resistance
more pathways for current to flow
therefore resistance v current ^
1/Rparallel= 1/R1 + 1/R2
W
energy
ability to do work
why does temp as current flows in resistor
result of electrical energy converted being converted into internal energy
as charge carriers move through conductors
power
rate of work done per unit time
transfer of energy from 1 object to another
power unit
watt(W) = 1 J.s^-1
triboelectric series
shows ease at which substance loses/gains electrons
energy consumed by appliances
kilowatthours
power rating (kw) X time (h)
cost of electricity
cost per kWh X no. of kWh
emf
the total energy supplied per coulomb of charge by the cell
voltage across battery terminals when no current flows in circuit
difference between ohmic and non-ohmic conductors
Non-ohmic conductors have a resistance that fluctuates with a change in the applied voltage, whereas ohmic conductors have a constant resistance that does not.
