Circuits Flashcards
Current
Flow of electrons in a circuit, carries electrical energy to components
Current in series
Same at all points in circuit - not used up
Current in parallel
The current in branches adds up to the total leaving and returning to the cell.
The current splits down each branch
Potential difference
A measure of how much energy is transferred in different parts of the circuit
Basically the energy to push the current around
Potential difference in series
The total V in all components = the voltage in the cell
Potential difference in parallel
Total voltage in each branch is the same
Potential difference in a battery
All the cells added up together, if some are facing the wrong way they cancel it out.
Resistance
The opposition to the flow of current (slows it down)
Resistance in series
Increases as more components are added
Resistance in parallel
Decreases as more components are added, because there are more paths for the current to pass through.
Charge
The property of being charged
A current of 1 ampere = 1 coulomb of charge flowing per second
Charge, energy and voltage?
Energy transferred = Charge flow × Potential difference
E = Q x V
Evil Queen Vacuuming
How to find the charge flow?
Charge flow = current x time
Q = I x T
(Queen It’s Time)
Resistor
Adds resistance to the electrical circuit
less energy is transferred per current
If the resistance is kept constant, what happens to the current and potential difference?
They will increase proportionally as long as the temp is the same
Fuse
Made up of thin wire that melts if too much current goes through
LDR
Light dependent resistor
Resistor affected by light hitting it
LED
Light emitting diode
Produce light when a current flows through them in the forward direction
Diode
Component that regulates potential difference
Resistance is high in one direction so current can only flow through the OTHER direction
What way does the current flow in a circuit?
From the negative end to the positive
When electrons return to the positive end what happens to the energy?
They have less energy than they did before they left the cell
Conventional current
Incorrect idea scientists and the electrons went from positive end to negative end
We still draw arrows like this however
Unit of current
Ampere (A)
How to measure current?
Use an ammeter
How is potential difference, charge and energy transferred linked?
1 volt means 1 joule of energy is transferred per coulomb of charge
How to measure voltage?
Voltmeter
Why are lamps dimmer when more lamps are connected in series?
Because voltage in series splits evenly so more added = less voltage for one lamp = less energy transferred to light energy
Ohm’s law
The current and potential difference is directly proportional as long as certain conditions are kept the same
Factors effecting ohms law?
These must be kept constant:
Resistance
Current in an ohmic resistor
Directly proportional to voltage
Because resistance doesn’t change when current is in creased
(If the temp is constant)
What must the ohmic resistor be for this law to work?
Temperature is kept constant
Why does adding more components in series decrease the energy transfer for each one?
Because in series the voltage in the battery is equal to the total voltage of components
So adding more components means you’ll have to share the voltage between them
Thus less energy transferred to them per coulomb of charge
Current and potential difference through a resistor
Directly proportional
Thermistor
Resistance depends upon the temperature
Variable resistor
Can change the resistance = not set
What does the potential difference/ current graph look like for a variable resistor?
Directly proportional
Because of Ohm’s law that they will be kept constant
What does the potential difference/ current graph look like for a Diode?
Almost 0 in negative values
Then becomes increasing after that like a curve
Because it has very high resistance in negative direction = no current
