Electricity Flashcards
how do objects become charged?
if friction causes electrons to be transferred
do like charges attract or repel?
repel
what happens if there is a potential difference between two points?
the negatively charged electrons will move towards the positive side
electrical current definition
the rate of flow of charge (how much charge flows through a point in the circuit in one second
what are electrical currents measured in?
amps (A)
what is the charge on an electron?
1.6 x 10^-19 coulombs
what is a potential difference?
the work done per coulomb charge that passes between the parts
what does a current need to flow?
potential difference
what is potential difference measured in?
volts using a voltmeter
what does a potential difference provide?
a push for the electrons (and current to flow)
electrical current equation
charge = current x time or Q=I x T
what is resistance
the opposition to the flow of charge
what is resistance measured in?
ohms
what is ohms law?
the current passing through a compound is directly proportional to the potential difference across it, provided the temperature is constant
what is resistance
the opposition to the flow of charge
what does increasing diameter do to resistance
decreases
what does increasing conductivity do to resistance
decreases
what does increasing length do to resistance
increases
what does increasing temperature do to resistance
increases
what does an iv graph show
the current passing through a component changes with potential difference
what is the resistance of a fixed resistor
- constant
what is the resistance of a filament bulb
increasing
what is the resistance of a diode
very high so no current flow
what is a series circuit
a circuit with only one loop
rule for current in a series circuit
current is the same at all points. only one route for the current to flow around
rule for potential difference in series circuit
shared between components , reduced by each resistance
rule for total resistance of series circuits
equal to the sum of the resistance of each component
problems with series circuits
if you remove a lightbulb or one burns out , they all go out
to have one bulb all the others must be on
what is a parallel circuit
a circuit with multiple loops
rule for total current in parallel circuits
total current is the sum of the currents through each branch
potential difference rule in parallel circuits
pd across each component is the same as the supply voltage
resistance rule in parallel circuits
total resistance is less than the resistance of the resistor with the least resistance
what affects resistance in an ldr
light intensity
where are ldrs useful
in circuits where light level drops below. a certain value so a light can be triggered to turn on
what is the bird rule for ldrs
brightness increases resistance decreases
what affects resistance in a thermistor
temperature
what can thermistors be used in
circuits to regulate temperature
what is the turd rule for thermistors
temperature up resistance down
