Electricity

Question 1

what is the base unit for Current?

Answer 1

Ampere

Question 2

What is the base unit for charge?

Answer 2

coulomb

Question 3

what is a good relationship between ampere and coulumb?

Answer 3

A = 1 C/s

1 C = A * s

Question 4

what is electrical potential formula? also known as coulomb’s law?

Answer 4

F = kq1q2/R^2

Question 5

what is directionality of pos and neg in electrical field arrow?

Answer 5

positive (tip) to negative (end)

Question 6

what is the units of coulomb’s law?

Answer 6

q: C
r: m
k: Nm^2/C^2 to cancel out q and r, leave us with newtons a force

Question 7

what happens if F is pos/neg?

Answer 7

if q1q2 are opposite signs: force is negative or attractive

if q1q2 are same signs: force is positive or repulsive

Question 8

What are the three equations needed to know for electricity?

Answer 8

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

Question 9

what is q vs Q

Answer 9

q: test
Q: source

Question 10

diple helps us think of torque, what are sign conventions of pos and neg:

Answer 10

pos - down, clockwise

neg - up, counter

Question 11

what do areas of denser field lines represent?

Answer 11

stronger field

Question 12

how does the longitudinal axis of an axon relate to a capacitor?

Answer 12

Axon: more pos extracel than intracel

- capacitor: linear spacing of some pos and neg charges

Question 13

How does torque relate to electicity in terms of equations?

Answer 13

T = Fdsintheta
F = qE, at distance of some midpoint

Question 14

pos vs neg work

Answer 14

pos work: work put into system
EX: test charge back up to source
neg work: spont done
EX: test charge down source infinitely distancd

Question 15

How can we relate work and electrical force? what are the respective equations?
- what is the relationship of work and energy here?

Answer 15

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

Question 16

What is electrical potential?

Answer 16

potential energy normalized for charge, so divide by q
V = kQ/r
- units are J/C

Question 17

What is the conceptial definition of voltage?

Answer 17

• 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

Question 18

How much work is done along a equipotential line? how can you explain this in an equation and conceptually?

Answer 18

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

Question 19

What is the direction of parallel electric fields pointing?

Answer 19

Points from positive to negative lines

Question 20

What denotes stronger electric field lines?

Answer 20

Closer together lines

Question 21

What are the units of electric field?

Answer 21

N / C or V / m