current electricity Flashcards
(45 cards)
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
