Unit 2: Electricity Flashcards
What are both units for current?
A/Amps/Amperes
And
CS-1
What is current?
Current is the rate of flow of charge (electrons)
What is the unit of charge?
Coulombs/C
What is the equation for current?
I=Q/t
Charge/time
Derive the equation for I=nAve
Volume = Area*Length
n is the number of electrons per unit volume
nAl = the total number of electrons in the volume
e = the charge of 1 electron
nAle = total charge
I = total charge/time
I = nAle/t
l/t = distance/time which is also velocity, therefore
I=nAve
What is a Coulomb
The unit of electrical charge
What is potential difference?
Potential difference is the energy required to push 1 coulomb of charge from 1 point to another
What does Ohm’s Law state?
Ohm’s Law States that potential difference across a component is directly proportional to the current through it under constant physical conditions
How is Ohm’s law represented?
V=IR
What is resistance?
Resistance is the measure of how difficult it is for the current to flow, a greater resistance requires a greater potential difference in order to produce a current
How does resistance occur?
Resistance occurs from the collisions between free electrons and ions within the conductor.
What does the gradient represent on an I-V graph and a V-I graph?
On a I-V graph the gradient represents 1/R
On a V-I graph the gradient represents R
How does temperature affect resistance?
When temperature increase the ions become more energise and have more kinetic energy causing more frequent collisions with electrons leading to a greater resistance
What is resistivity?
Resistivity is the measurement of a materials resistance
What is the equation for resistivity?
ρ = Resistance X Area / Length
How does a thermistor work?
If temperature goes down, resistance increases, if resistance increases voltage share increases.
How do LDRs work?
If light levels decrease resistance increases, therefore voltage share increases.
What is superconductivity?
It is when a material will conduct with 0 resistance.
How do materials become superconductors?
A material will become a superconductor once cooled down to a certain temperature called the transition temperature. This can be achieved using liquid nitrogen and liquid helium.
What are uses of superconductors?
Superconductors can be used to make magnets which can later be used in making floating vehicles, MRI scanners, particle accelerators
What are potential dividers?
Potential dividers are circuits which deliberately divide the potential difference between 2 or more components. The PD is shared based on resistance.
What is emf?
the electromotive force is the energy from a supply converted into electrical potential energy per coulomb of charge passing through it
How is the potential difference measured using EMF giving the equation and explaining it
V = E - Ir
The potential difference is equal to the EMF taken away by the current multiplied by the internal resistance of the supply.
