Electrostatics III Pt II

  1. Calculating the Electric Potential 
    Knowing the potential energy, we can calculate the electric potential of a charge q at a point using what equation?
    V = Ue/q
  2. The parallel-plate capacitor creates a uniform electric field (state the formula) 
    The plates have area A and separation d. Let Ue = 0 when a mobile charge q is at the negative plate (x = ___). The charge's potential energy at any other position x is then the amount of work necessary to move the charge from the ______ ______ to that position 
    The hand does work on q to move it ______ against the field, thus giving the charge electric potential energy
    Image Upload 1
    • E = Q/ε0A
    • (x = 0)
    • negative plate 
    • uphill
    • Image Upload 2
  3. The hand push the charge q towards the positive plate at a constant speed. Thus, Fhand = ____ = ____
    State the formula for the work to move the charge to position x: 
    W (2)
    State the formula for the work to move the mobile charge to position x within the contex of potential energy: 
    W (2)
    Image Upload 3
    • Fhand = Fe = qE
    • W = (force)(displacement) = (Fhand)(x) = (qE)(x)
    • W = ΔK + ΔUe = (qE)(x)
  4. The electric potential of the parallel-plate capacitor at position x, measured from the negative plate (Ue = ___, V = ___), is: 
    State the formula for V (3)
    The electric potential increases linearly from the ______ plate (x =  ___) to the ______ plate at (x = ___)
    The potential difference ΔVc between the two capacitor plates is: 
    ΔVc = _______ = _____
    Image Upload 4
    Image Upload 5
    • (Ue = 0, V = 0)
    • V = Ue/q = Ex = (Q/ε0A)(x)
    • negative plate (x = 0)
    • positive plate (x = d)
    • ΔVc = V+ - V- = Ed
  5. A 2-D equipotential map is represented below. The green dashed lines are _________ lines or simply _________.
    Image Upload 6 Image Upload 7
    • equipotential lines
    • equipotential
  6. Image Upload 8
    Image Upload 9
    See notes
  7. To find the electric potential due to a single fixed charge q, we first find the electric potential energy when a second charge q' is a distance rB away from q
    ΔUe = ______
    Take (Ue)A = 0 to be at a point infinitely far from q (i.e. rA → ∞) for convenience. This is a good reference point as the influence of the point charge q goes to _____ as we get _____ far from the charge 
    Image Upload 10
    • ΔUe = Wby the hand
    • zero
    • infinitely
  8. The force on q' gets larger as it approaches q. Thus, work done is not by a constant force and cannot use the equation W = Fd to find the work for a ______ ______ q'
    Image Upload 11
    moving charge q'
  9. An exact calculation finds the electric potential energy of two point charges separated by distance r is: 
    Ue = ______
    In the case where q and q' are opposite charges, the potential energy of the charges is _______. q' _______ toward fixed charge q. Uelec = 0 when q' is ______ far from q. As q' approaches q it gains ______ energy and loses ______ energy
    The y-axis is Uelec
    Image Upload 12
    • Ue = (ke)(qq'/r)
    • negative 
    • accelerates 
    • infinitely 
    • kinetic energy
    • potential energy
    • Image Upload 13
  10. For a charge q' that is a distance r from a charge q, the electric potential is related to the potential energy by V = ____. 
    The electric potential at distance r from a point charge q is: 
    V = ____ = ____ = ____
    Only the source charge appears in this expression. (The source charge creates the _______ _______ around it)
    • potential energy
    • V = Ue/q'
    • Image Upload 14
    • electric potential
  11. Electric potential at distance r from a point charge q
    Restate the formulas for V(3)
    Image Upload 15
    Image Upload 16
  12. Image Upload 17
    • C. assume charges are positive unless told otherwise.
    • Potential at point A: VA = keQ/rA
    • Potential at point B: VB = keQ/rB
    • VB/VA = (keQ/rB)(rA/keQ) = rA/rB = (1mm/3mm) = 1/3
  13. The electric potential at a distance r > R from the center of a sphere of radius R and with charge Q is the same as the _____ _____ at a distance r from a point charge.
    • electric potential 
    • Image Upload 18
  14. The potential V0 is the potential at the surface of the charged sphere
    V0 = _____ = _____
    The charge for a sphere of radius R is therefore: 
    Q = _____
    The potential outside a charged sphere: 
    V = ______ = _______ = _____
    The potential ______ _____ with distance from the center
    Image Upload 19
  15. Image Upload 20
    • D. V = keQ/r = (R/r)(V0)
    • V0= [(V)(r)]/(R) = (30*15)/5 = 90V
  16. Image Upload 21
    Check notes
  17. V is constant everywhere on the surface of a charged conductor in equilibrium. ΔV = ___ between any two points on the surface. No work is required to move a _____ _____ between any two points on the surface. The surface of any charged conductor in electrostatic equilibrium is an ________ ______. Why is it that the electric potential is constant everywhere inside the conductor and equal to the value at the surface.
    • ΔV = 0
    • test particle 
    • equipotential surface
    • Because the electric field is zero inside the conductor
  18. Consider a solid metal conducting sphere, Radius is R, total charge is Q. The electric potential is a function of ____. The electric field is a function of ____
    Image Upload 22
    • r2
  19. Suppose there are many source charges, q1, q2... the electric potential V at a point in space is the ____ of the _______ due to each charge. So V = _____ = _____
    Define ri  
    The electric potential is a simple _____ ____ which is easier to find
    • sum of the potentials 
    • Image Upload 23
    • ri: the distance from charge qi to the point in space where the potential is being calculated 
    • scalar sum
  20. Label the diagram  (4)
    Image Upload 24
    Image Upload 25
  21. Image Upload 26
    B and D
  22. Image Upload 27
    check notes
  23. Vector E and V are not two distinct entities, but instead, two different perspectives or two different mathematical representations of?
    Vector E at a point is _______ to the equipotential surface at that point 
    Vector E points in the direction of _______ potential
    • Two different perspectives or two different mathematical representations of how source charges alter the space around them
    • perpendicular
    • decreasing
  24. Vector E is ______ to the equipotential surface everywhere. Vector E points ______ in  the direction of ______ V. The field strength is ________ ________ to the spacing d between the equipotential surfaces
    • perpendicular
    • downhill 
    • decreasing 
    • inversely proportional 
    • Image Upload 28
  25. A positive charge speeds up as it moves from ______ to ______ potential. The work required to move a charge, at a ______ _____, in a direction opposite the electric field is: 
    W = ______ = _____ = _____
    Constant speed → Fhand = ____ = ____
    Thus Image Upload 29 = ____ (explain d)
    • higher to lower potential 
    • constant speed 
    • W = Fhand = ΔUe = qΔV
    • Fhand = Fe = qE
    • Image Upload 30 , where d is the distance between the two equipotential surfaces
  26. Image Upload 31
    D. ΔU = eΔV = e(100V) = 100 eV
  27. Below are the three important arrangements of charges. Both electric field lines and equipotentials are shown. Remember the electric field vector is ______ to the equipotential surface. 
    In point charges and electric dipoles, field lines are everywhere _________ to equipotentials. The electric field is _______ where the equipotentials are closer together. For electric dipoles in a Parallel-plate capacitor, field lines point from ______ to ______ potential. For the capacitor, the field is ______ and so the equipotential spacing is _______
    • perpendicular 
    • perpendicular 
    • stronger
    • higher to lower potential 
    • uniform 
    • constant
    • Image Upload 32
  28. Image Upload 33
    • E field always points from high to low so possibly B E C
    • As the E Field goes up, the distance between the lines gets smaller and smaller so C
  29. Image Upload 34
    • A: Ans = B Distance is the shortest so E field is the strongest 
    • B: Ans = D
    • C and D check notes
  30. Properties of a conductor in electrostatic equilibrium: 
    1. All excess charge is on the ______
    2. The electric field inside is ______
    3. The exterior electric field is ______ to the surface 
    4. The electric field strength is largest at the ______ ______
    Image Upload 35
    • surface
    • zero
    • perpendicular 
    • sharp corners
    • Image Upload 36
  31. Image Upload 37
    • Wire makes it so the potential is the same in both spheres.
    • v1 = kQ1/r1
    • v2 = kQ2/r2
    • so:
    • Q1/r1 = Q2/r2
    • 2nC/1cm = Q2/2cm
    • Q2 = 4 nC
  32. The electrical activity of cardiac muscle cells makes the beating heart an ______ ______. A resting nerve cell is _______; the outside is ______ and the inside is ________. Initially, all muscle cells in the heart are polarized, until an electrical impulse from the heart triggers the cells to ______, moving ions through the cell wall until the outside becomes ______. This causes the muscle to contract
    • electric dipole
    • polarized
    • positive
    • negative
    • depolarize
    • negative
  33. The depolarization of one cell triggers a wave of ________ to spread across the tissues of the heart. At any instant, a boundary divides the negative charges of _______ cells from the positive charges of cells that have not yet ________ in the heart. This separation of charges creates an electric dipole and produces a ______ ______ field and ______
    • depolarization 
    • depolarized 
    • depolarized
    • dipole electric field and potential
  34. The boundary between polarized and depolarized cells sweeps rapidly across the atria. At the boundary there is a charge separation. This creates an ______ ______ and an associated dipole moment 
    Label the diagram
    Image Upload 38
    • electric dipole 
    • Image Upload 39
  35. A measurement of the electric potential of the heart is an invaluable diagnostic tool. The potential difference in a patient is measured between several pairs of ________. A chart of the potential differences is the __________, also called an _____ or an _____. With each heart beat, the wave of depolarization moves across the heart muscle. The dipole moment of the heart changes _______ and _______
    • electrodes
    • electrocardiogram
    • ECG or an EKG
    • magnitude and direction
  36. The records of the potential difference between the two electrodes is the ________. 
    The potential differences at a, b, and c correspond to those measured in the three stages shown to below
    • electrocardiogram 
    • Image Upload 40
Author
chikeokjr
ID
346654
Card Set
Electrostatics III Pt II
Description
Electrostatics III Pt II
Updated