Electricity Flashcards
current
the measure of the flow of electrons around a circuit. Measured by amperes/ amps (A)
Potential difference
Same as voltage.
The fore driving the flow of electrons
Measure by volts (V)
Resistance
Anything that resists or slows the flow of electrons.
Measured by ohms
The current flowing through a component depends on …
1) The potential difference around the component
2) The resistance across the component
Relationship between current and resistance
The greater the resistance across the component, the small the current that flows, for a given potential difference
Current in a circuit travels from…
positive to negative
charge
a measure of the total current that flowed within a period of time.
More charge passes around the circuit when a larger current flows
what is charge measured in
coulombs
equation for charge, current and time
charge = current x time
the equation for potential difference, current and resistance
potential difference = current x resistance
Required practical - length of the wire
1) set up the wire
2) connect the wire with two crocodile clips
3) close the switch, record the current and potential difference
4) open the switch, move the second crocodile clip another 10 cm away
5) close switch and record the current and potential difference
6) repeat this for a number of different lengths od the test wire
7) use measurements to calculate the resistance
8) plot a graph of resistance against wire length
Required practical - length of the wire - results
resistance is directly proportional to the length of the wire, so when the length of the wire increases, resistance increases
Required practical error
zero error - it is difficult to get the crocodile clip exactly at 0cm and there is some resistance caused by the contact between the crocodile clip and the wire. we cannot reduce this risk so we need to subtract the zero error from all our readings
Heating effect - if the temperature of the wire increases, the resistance increases, to reduce this we can keep the pd low so that the current is low, reducing heating in the wire. And turn the current off in between readings and only turn it on when we are taking readings to reduce the heating of the wire
series circuit
one loop, no branches so the current can only flow in one path.
if you remove or disconnect one component, the circuit is broken and they all stop. So only a few things are connected in series circuits.
current in series circuit
current is the same
parallel circuit
A parallel circuit contains branches, so the current splits
if you remove or disconnect one of the components, it hardly affects the others.
current in parallel circuit
current is shared between branches, so the current in the branches adds up to the total current leaving the cell
convential current
current that flows from the positive end of the cell to the negative end of the cell
what does pd tell us about energy transferred
a pd of 1 volt tells us that 1 joule of energy is transferred for each coulomb of charge that is moving through the circuit
electric field
An electric field is a region where charges experience a force
relationsip between closeness and the strength of the field
as you decrease the distance between the charged object, the strength of the field increases, so the forces between them gets bigger
electric field lines
electric field lines go from positive to negative.
they are always at a right angle to the surface, the closer the lines are, the stronger the field is
