physics- electricity Flashcards
what charge does an electron has
. One electron has a charge of 1.6x10-19 C.
what is charge measured in
Charge (Q) is measured in Coulombs (C)
what is 1 coulomb defined as
1 Coulomb is defined as the amount of charge that passes in 1 second when the current is 1 Ampere
what does a current of 1a mean
A current of 1A means that
1 coulomb of charge flows past that point every second
what is current
Current (I) is the rate of flow of charge, and is measured in Amperes (A).
what is potential difference measured in
voltages
what does 1 voltage mean
1V
means that 1 Joule of work is done in pushing 1 coulomb of charge through a particular area/component
where are voltmeters placed in a circuit
Voltmeters are placed in parallel and have infinite resistance, so they measure current between
2 points in a circuit.
what is resistant defined as
the ratio of voltage to
current
power
Power (P) is measured in watts (W)
watts
the rate of transfer of energy.
1W is the transfer of 1 Joule of energy per second.
what happens when cells are connected
When cells are connected in series, the total voltage supplied to the circuit is the sum of the individual voltages of the cells. However, when
identical cells are in parallel with each other, the total voltage supplied
to the circuit is equal to the voltage of just one of the cells
what is a cell
A cell is a single electrical energy source which uses chemical reactions to produce a current*
how to work out total voltage in a line
add them all together
resistance in series circuit
add them
resistance in parrellel
1/r and add .
CONSERVATION OF CHARGE –
“The total charge flowing into a junction of wires must equal the total
charge flowing out of the wires”.
This leads to…
KIRCHOFF’S FIRST LAW
– “The sum of the currents flowing into a junction of wires must equal the sum
of the currents flowing away from the junction of wires”.
what happens with currents in parrelel and currents in series
In a parallel circuit, the current splits. In a series circuit, the current is constant throughout
what is the conventional current
The arrow points in the direction of
conventional current, which flows from positive to negative.
Although electrons themselves flow from negative to positive,
why is the conventional current the opposite way around
the convention was decided years before this was discovered,
so when discussing currents, we say that current flows from
positive to negative (The tall end of the cell is the positive
end).
why is the conventional current the opposite way around
the convention was decided years before this was discovered,
so when discussing currents, we say that current flows from positive to negative (The tall end of the cell is the positive end).
voltage
shared in series circuits
same in parrellel circuit
R1 V1
R2 V2
The ratio of the voltages is the same as the ratio of
the resistances.
what is a diode
if a diode points in the direction of the conventional current nothing occurs. if it is in the opposite direction then it is in the reverse bias and no charge can go through
Transformers
A transformer is a device that changes voltage and current, whilst keeping power the same.
