test 3
can electrostatic charge be created/destroyed
no it can only be transferred
what materials conduct metals
ones that allow changed to move relatively easy due to atomic structure
materials that insulate
make it difficult for charges to move
what is 1 ampete (amp)
6.25 x 10^18 electrons
charge of one electron
1.6x10^-19
what is a positive columb (C)
6.25 x 10^18 protons
what is a negative columb (C)
6.25x10^18 electrons
to find charge of columbs
ne =Q x 6.25 x 10^18
or Q=ne/6.25x10^18
ne = electron number
what is induction
if charged object is brought near neutral conditional object it will induce charge into neutral object
why is induction
when the charged object goes next to tye neutral object, the electrons in the neutral object go closer or further from the charged object depending on the charge, creating an imbalance in the perviously neutral object, creating a charge
what is a current
moving electrons theough repelling/attracting
what is a current defined as
the amount of charge flowing per second measured in ampetes (amps/A)
what is the equation for current
I=Q/t = (ne x 1.6 c 10^-19)/t
I is current (A)
Q is charge (C)
t=time (seconds)
what is a direct current
circuits using direct current meaning charge only flows in one direction (batteries)
what is an alternating current
direction changed constantly (periodically moves back and forth between negative and positive) (sin graph)
how to measure a current
an ammeter is placed in circuit and charge is measured as electrons flow through (how many pass)
what is electric potential energy (voltage)
the PE stored per unit of charge (positron)
generally asked abt change in voltage
equation for change in voltage
(triangle)V=E/Q
V is voltage change in volts (1V is 1J/C)
E is electric potential energy used in joules
Q is change in columbs
what is voltage defined as
energy lost by each columb of charge
as charge progresses around circuit energy is lost into components
how is voltage/diff measured irl
voltmeter is placed outside of circuit, across load measuring and the before and after load is measured and diff is found
what does E= triangleV x Q tell us
if Q= I x t then
E= triangleV x I x t
what happens fo the energy as it passes through resustor
resistor gets hot as the electrical enegy becomes thermal
this means that W=QV
what is the energy transfer of circuits
circuits can be transformed to heat, sound or light from the electric potential energy
what does the amount of energy transferred from EPE depend on
amt of PE used by each charge (V)
nunber if charges passing through section (Q)
what is the pitential diff
the voltage drop
the change in voltage between two locations
what is resistence
the ratio of voltage drop across conductor fo current flowing through it
what is equation of resistance
R=V/I (Ohms Law)
measured in Ohms or horse shoe thing
Ohm=V/A
properties of Ohmic devices
constant resistance
fixed ratio of V/I (straight y=x graph of ratio)
law of conservation of charge
charge flowing into point must equal charge flowing out of point
thus I(in)=I(out)
principle of conservation of electrical energy
all circuits
in any closed loop sum of voltage =sum of EMF(s) in loop (energy supply)
thus
V(end)-V1-V2-V3=0
series circuit current rules
charge flowing in = charge flowing out
thus I(in)=I(out)
thus current same at all points
series circuit voltage rules
sum of voltage drops over each resistor= EMF power supply
this V(supply)=V(R1)+V(R2)
series circuit toal resistence rules
R(T)=R1+R2
parallel circuit charge rules
same I(in)=I(out)
however
current divided into two when branch/node
(I1 and I2)
therefore I(in)=I1+I2=I(out)
parallel circuits voltage rules
multiple loops
each loop must adhere to conservation of energy
voltage measured across both branches same as original
parallel circuit resistent rules
V(supply)/R(T) =V1/R1 +V2/R2
then because V(supply) =V1=V2
therefore 1/R(T)=1/R1 + 1/R2
what is power
product of voltage drop and current flowing through
total power is what in series and parallel
P1 + P2 + P3 etc
when does a short circuit occur
when path of zero (negligible) resistance between volt drop
what can short circuits lead to
very high current
thus fire
also drains source of voltage very quick
what is a transducer
a component of a circuit that receives energy in one form and gives out energy in another form
what is an input transducer
a transducer that converts energy into smt that a circuit can use (electrical)
what is a potentiometer
a variable resistor that can have uts resistance changed/controlled
how does a potentiometer increase resistance
by making the current flow through more resistant material, increasing ohms of resistance
what is a thermoresistor
a type of variable resistor that acts based on temperature
set to a certain temp and acts when temp isnt in that range (fridge)
what is a light dependant resistor
a resistor that only acts when it has enough or little enough light on it (streetlamps)
what is a diode
a signal processing device with infinite resistance until a certain amt of voltage is fed into it
when a diode receives enough voltage what happens
a bridge is created that allows current to flow through freely
if diode is positive biased what occurs
voltage drop will always be Vs
current flows
if diode is negative biased what happens
resistance is always infinite
current doesnt flow
what is an active wire
the wire that the electricity comes through prior to the resistor/switch (top left)
rough RMS (V) of active wire
avg of 0-240 or -240-0 (can go up to 330/-330)
what is the neutral wire
the wire that receives if positive or hives if negative from or to the active wire (top right)
why is the switch on the active wire
to prevent the electricity from going into circuit/machine which prevents possible injuries as machine doesnt have left over electricity
what is earth wire
wire connected to conductive metal rod to absorb excess voltage if circuit breaks
why may a machine not have an earth wire
if the machine is double insulated with metal and plastic then elec cant escape and jnjure anyway
what is residual current device
if current not same between in/out (human intervention) then turns off circuit in 20 milliseconds
is RCD and circuit breaker diff
yes, circuit breaker protects overloads and short circuits, RCD checks current and stops if bad
what is charge
coulumbs (C) or Q