Electricity Flashcards
what is the base unit for Current?
Ampere
What is the base unit for charge?
coulomb
what is a good relationship between ampere and coulumb?
A = 1 C/s
1 C = A * s
what is electrical potential formula? also known as coulomb’s law?
F = kq1q2/R^2
what is directionality of pos and neg in electrical field arrow?
positive (tip) to negative (end)
what is the units of coulomb’s law?
q: C
r: m
k: Nm^2/C^2 to cancel out q and r, leave us with newtons a force
what happens if F is pos/neg?
if q1q2 are opposite signs: force is negative or attractive
if q1q2 are same signs: force is positive or repulsive
What are the three equations needed to know for electricity?
Coulomb’s law: F = kq1q2/r^2
- test charge q
E = F/q
This helps us derive ?
E = kQ/r^2
-only need source charge Q
what is q vs Q
q: test
Q: source
diple helps us think of torque, what are sign conventions of pos and neg:
pos - down, clockwise
neg - up, counter
what do areas of denser field lines represent?
stronger field
how does the longitudinal axis of an axon relate to a capacitor?
Axon: more pos extracel than intracel
- capacitor: linear spacing of some pos and neg charges
How does torque relate to electicity in terms of equations?
T = Fdsintheta F = qE, at distance of some midpoint
pos vs neg work
pos work: work put into system
EX: test charge back up to source
neg work: spont done
EX: test charge down source infinitely distancd
How can we relate work and electrical force? what are the respective equations?
- what is the relationship of work and energy here?
W = Fd F = kQq/r^2 - distance of work is radius > F = W/r W = kQq/r units are Joules, so this is also eqt for potential energy
What is electrical potential?
potential energy normalized for charge, so divide by q
V = kQ/r
- units are J/C
What is the conceptial definition of voltage?
- how much energy required to move charge to point in electrical field (per unit charge)
- if spontaneous, how much energy is released
- aka if work is negative
How much work is done along a equipotential line? how can you explain this in an equation and conceptually?
potnetial difference is change in voltage
- when there is no change in voltage along eq line, work is = 0
- no matter what the chrage is, the change in voltage will be 0
- no work is done
What is the direction of parallel electric fields pointing?
Points from positive to negative lines
What denotes stronger electric field lines?
Closer together lines
What are the units of electric field?
N / C or V / m
