# Physics - Electricity .txt

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1. What is Coloumb's law? (equation) What does it mean?
describes force between two charges

F = k (q1q2) / r

k = 9 x 109
2. Coloumb's law resembles what? But?
gravitational force (G)(m1m2)/(r2)

• but, gravitational force is attractive
• electrical force is repulsive
3. electric field - in what way are the lines drawn? What does the length of the line indicate?
(+) ----------------> (-)

length = strength

(smaller is stronger)
4. What is the electric field created by charge Q?
E = k x (Q)/(r2)
5. What is the force felt by charge q in the electric field E?
F = E x q
6. What makes and feels the field?
Q makes the field

q feels the field

[F = k x (Qq)/(r2)
7. What is the potential energy of of the charge in electric field?
Potential energy (U) = force x displacement (like ugh)

U = Eq x h
8. How does potential energy change when moving perpendicular to electric field?
doesn't change

same way that moving parallel to surface of the earth doesn't change gravitational potential energy
9. What is an electric dipole?
created by 2 opposite charges with equal magnitude
10. (+) and (-) fall/rise to lower/higher potential?
+ charge falls to a lower potential

- charge rises to a higher potential
11. high/low potential and +/- potenital
• high potential = + potential
• low potential = - potential
12. How do we measure movement of a charge?
current (A)
13. So, what is current? (How is it measured)
Coloumbs/second
14. Current flows in what direction (relative to potential energy)
current flows from high potential to low potential
15. In what direction does current flow (relative to electron flow or electron velocity)?
current moves in opposite direction of e- flow
16. conducting electricity: what are good conductors and poor conductors?
• good = allow e- to flow freely [metals]
• poor = hold e- tightly in place [resistors]
17. What is induction?
charging a conductor
18. circuit equations: current, voltage, resistance, capacitance
V = IR

I = Q/t

C = Q/V
19. what is capacitance?
ability to store charge per unit voltage [Q/V]
20. voltage is the same thing as...... and it depends on
potential energy

depends on distance
21. plates that are further apart will have greater/less voltage and capacitance?
greater voltage

less capacitance
22. What is a capacitor?
temporarily stores energy in a circuit
23. What is the separation of charges in a capacitor?
emf between the plates
24. what is resistance?
resistance to flow of charge
25. resistance is directly proportionate to what?
length of wire

[R = density x (length/area)]
26. resistance and temperature
resistance increases with temperature

[thermal oscillations impede with flow]
27. Kirchoff's Rules:
- amount of current flowing in and out
- voltage around the circuit
-battery
- amount of flow in = amount of flow out

- votalge around any path in circuit must sum = 0

- battery adds energy to circuit
28. How does battery add energy to the circuit?
increases voltage from one point to another

29. Diaelectric constant (K)
substance between plates of a capacitor

• -must be insulator to separate charge
• -resists creating EF, in order to store energy
30. Resistors in series/parallel

what is constant?
series = add [current is constant]

parallel = 1/R [voltage is constant]
31. what is the terminal voltage? (equation)
V = emf - IR
32. AC Current - what's going on?
e- don't move in one direction,

they oscillate back and forth
33. maximum current and maximum velocity in an AC Current
Vmax = sqrt.(2) x Vmax

Imax = sqrt.(2) x Imax
34. What creates a magnetic field?
charging electric field

currents (moving charges) creates the magnetic field
35. + and - of electric field corresponds to what in magnetic field?
north and south

north = + and south = -
36. In what direction do magnetic lines point?
north -------> south
37. Doess a stronger magnetic field have closer lines, or further apart?
closer lines = stronger fied
38. How does the KE of a particle moving through the magnetic field change?
no work done by the magnetic field, means no change in KE due to the magnetic field
39. What is magnetic force?
F = q x V x B x sin(0)
40. force is applied in what direction relative to both velocity and magnetic field
force is perpendicular to both velocity and magnetic field
41. What is the work done by magnetic force?
no work:

because it's perpendicular to velocity
42. What way does magnetic field act?
like centripetal force (mv2/r)

because charged particle moves in a circle
43. What will move through a magnetic field with a smaller radius: a proton or an electron
electron:

because it has smaller mass [F = mv2/r]
44. Right Hand Rule
thumb = direction of current

fingers = direction of magnetic field

palm = direction of force
45. What results from a change in magnetic field?
an electrical field
46. What happens to the mechanical energy in a magnetic field when it is changed and creates an electric field?
mechanical energy to create the field is dissipated as heat
47. What is the magnetic flux?
number of magnetic fields running through the loop
48. what does change in magnetic flux do?
induces an emf
49. What is a magnetic field generated by?
a moving charge
50. moving charge experiences what when moving through a magnetic field?
force = qvBsin0
51. In what direction is this force?
perpendicular to velocity and magnetic field (B)
52. At equilibrium, in an electric and magnetic field, what is the net force acting on a particle?
0

force from electric field = force from magnetic field

Eq = qvBsin(0)
53. How can we find the acceleration or distance of a particle traveling through an electric or magnetic field
F = ma

set force (Eq) or (qvbsin) = mass x acceleration

distance = (1/2)at2

## Card Set Information

 Author: natalieplana ID: 82963 Filename: Physics - Electricity .txt Updated: 2011-05-01 15:13:34 Tags: NPMCAT Folders: Description: Electricity and Magnetism Show Answers:

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