electricity Flashcards
what is energy
work done by a force of one newton when it moves one metre in the direction of action of the force
what is frequency
one oscillation per second
what is current
when 1 coulomb of charge flow past a point in one second
what is potential difference
when 1 joule of energy is transferred to ( or form ) 1 coulomb of charge
what is power
when 1 joule of energy is transferred in 1 second
what is charge
1 coulomb is the amount of charge delivered by 1 ampere of current in 1 second
what is resistance
transmits a current of one ampere when subjected to a potential difference of 1 volt
what is resistivity
resistance of unit length of wire with unit cross sectional area
what is the voltage called that starts a diode and what is the the voltage
trigger voltage 0.7v
what does a diode on a graph look like
follows the line of the x axis until the trigger voltage which causes a gradual gradient
what is Kirchhoff’s first law
total current into a junction = total current out of a junction
what is EMF
electromotive force
how many electrons are required to carry 1 coulomb of charge
no. of electrons = 1C/1.6x10^-19C = 6.25x10^18
what is the equation for volts
energy transferred / charge
what are the 2 types of circuits
-series
-parallel
list 12 electrical components
-switch
-cell
-lamp/bulb
-resistor
-variable resistor
-LDR
-thermistor
-diode
-LED
-ammeter
-voltmeter
-fuse
what is the equation for resistance in a series circuit
Rt = R1 + R2… + Rn
what is the equation for resistance in a parallel circuit
1/Rt = 1/R1 + 1/R2… + 1/Rn ( inverse)
what is electrical current
electrical current is the rate of flow of charge.
what is the equation for electrical current`
I = ΔQ/Δt
what is the rearranged equation for amps
ΔQ = IΔt
how does resistance correlate with resistivity
they are directly proportional
how does resistance correlate with with length
they are directly proportional
how does resistance correlate with with the cross sectional area of the wire
they are inversely proportional
what is the equation for resistivity
Ρ = RA/l (resistivity = resistance*area / length)
what is the equation for resistance using resistivity
R = ρl/a ( resistance = resistivity*length/area)
define resistivity
resistance is a constant material property, whereas resistance is a sample/specific, depending on a materials resistivity, length and cross sectional area.
how do thermistors work
an increase in temperature causes an increase in resistance and vice versa, so the resistance varies with temperature
most thermistors are negative temperature coefficient what does this mean
this means if the temperature increases the resistance of the thermistor decreases and vice versa
describe resistance in terms of particles
the electrons collide with the vibrating atoms which impede their flow, so the current decreases
doubling the length of the wire will
will double the resistance
doubling the cross sectional area of a wire will
half the resistance
what is conventional current flow
Flow from positive to negative, used to describe the direction of current in a circuit.
what does a diode do
Components that allow current through in one direction. In the correct direction, diodes have a threshold voltage (typically 0.6 V) after which current flows normally.
what is the EMF (electromotive force)
The energy supplied by a source per unit charge passing
through the source, measured in volts
what is internal resistance
The unavoidable resistance any power source will have that makes it harder for current to flow through the source. It causes energy to be dissipated in the source.
describe how a potential divider works (3-4 marks)
-combination of two or more resistors in series.
-These result in the potential difference of the circuit being split into a specific ratio depending on the resistance of the resistors.
-They can be used to get a specific output voltage from the circuit.
