Resistance (re) Flashcards
What is potential difference equivalent to? (also what’s its units?)
Voltage (JC^-1)
Define electro motive force
The energy converted to electrical energy per unit of charge
Define potential difference
A measure of energy, per unit of charge, transferred between two points in a circuit
[Energy converted from electrical potential energy to some other form per coulomb of change flowing from 1 point to the other]
(this is a retarded ass answer)
i mean that class was always ^^ if u know what i mean
What the equation that relates voltage to energy changes in a circuit per unit charge? (retarded ass question)
(actually not too icky yano)
J = V x c
Work done = voltage x charge
Look at the beginning of the first pages of the booklet
(because i cba to like explain this visual tasking type shit)
am pretty sure this part was “partly” useless
Well, u better get a good mark for this one, although this isn’t ideal or efficient (possibly?), it is what it is, Have Fun!
i mean, it appears to be?
What is Ohms law?
The current in a metal wire at a constant temp. is proportional to the p.d. across it
What is the equation for voltage?
V = IR
Voltage = Current x Resistance
Define resistance
Anything that opposes the flow of charge (aka current)
What’s resistance measured in?
[but there’s also a chance that there may be more for this…?]
lol i think that was useless
Ohms (that symbol that looks like a pimple)
[we shall see]
agreeable
Number 1 way of finding P?
(power)
Current x Voltage
Number 2 way of finding P?
(power)
Current^2 x Resistance
I^2 x R
Number 3 way of finding P?
Voltage^2 divided by Resistance
V^2 / R
How does resistance work specifically in 3 steps?
- As free electrons move thru wire, they collide with atoms + with one another, which slows them down
- Some of the energy is transferred to the atoms, makes them vibrate = increases temp
- Ye that’s resistance?
What is the equation for resistivity?
Resistivity = (Resistance x Cross sectional area) divided by length
p = (RA)/L
State what each of these symbols are:
p = ?
R = ?
A = ?
L = ?
p = resistivity
R = resistance
A = cross sectional area
L = length
If temp. is low in a metal wire, what dat mean for the resistance?
(3 steps)
At low temperatures:
- Electrons can drift past positive metal ions with ease
- Cuz few collisions to slow em down
- Resistance is low
If temp. is high in a metal wire, what da mean for the resistance?
At high temperatures:
- Positive ions vibrate with greater amplitude
- Electron-in collisions more frequent
- Flow of electrons slowed down
[current reduced]
RESISTANCE IS HIGH
What’s the jig with resistance and resistivity
They directly proportional
You know what that means?
If resistance increases, resistivity increases
Define semi conductor?
Component that can partially conduct electricity ig
+
changes resistance based on temp
Why resistivity decrease with increasing temp. in semi conductors?
(3 steps)
- More electrons break free of their atoms
- Increase in number of electrons available for conduction
- Resistivity decreases
Define super conductor?
A material that has 0 electrical resistance at absolute zero temperature
What name given to a temp, for a conductor that its resistance drops rapidly due to temp. change?
The Critical/transition
What’s superconductivity?
(gl man)
When it has 0 electrical resistance when temp. is either at absolute zero (0 degrees kelvin or -273 degrees Celsius) to liquid nitro temps. (77k, -196 degrees Celsius)
gagagaga
what?
googoogoogo
baby as hell
3 examples of use of superconductors?
- Maglev train
- MRI scanner
- Particle accelerators
Explain maglev train
(superconductor) 2 things
Makes train levitate off track1. To produce strong magnetic field2. no resistance = higher speeds
- To produce strong magnetic field
- no resistance = higher speeds
Explain MRI scanner
(superconductor) 4 things
- good for non-invasive medical diagnosis
- Strong magnetic field aligns hydrogen atoms in body
- Radio waves absorbed = emitted by hydrogen atoms
- Image of body produced
Explain particle accelerators
(superconductor) 2 things {that was separated} <– fuck is the use of that symbol
u tell me bro, what is that symbol?
- Magnetic field keeps the particles in a beam
- And steers them around the circular detector
