Karteikarten
Physics Exam 1
Karten in diesem Stapel (66)
- 1—
- 2Define vectormagnitude (number) and direction
if direction added makes sense it is a vector like driving 50mph west vs a room is 70 degrees west - 3find x and y how would you find hypotenuse and angle if you had x and y
- 4A + B
- 5finding angle relative to the positive x-axis based on different quadrants
- 6Mass differences in protons, neutrons, and electronsProtons and neutrons are very similar in mass while electrons are very small
- 7Unit for chargeCoulomb (1.60x10^-19 C)
- 8In nature, atoms are normally found...with equal numbers of protons and electrons so they are electrically neutral
by adding or removing electrons it will acquire a new electric charge - 9q = Neq: charge
N: # of e- we add or sub
e: coulomb (1.60x10^-19) - 10Conductors, Insulators, Semi-Conductorconductors: substances can conduct electric charge and allow flow of e- (all metals/coppers is best)
Insulators: materials that conduct electric charge poorly and stop flow of e-; *almost all e- remain bound to parent atom; plastic, rubber, wood* - 11Charging by contact vs inductioncontact: ebonite rod that is charged touching and transferring e- to sphere (stand is insulated so they do not leave sphere) *whenever an e- is transferred to the rod, proton to fur (doesn't change net charge)*
induction: get close, repel e-, attract protons, with a grounding wire you can make e- leave sphere and give it a positive charge (only positive because only e- move vs p/n vibrate) *w/o wire + move towards - rod, makes one side +, one - but if move rod away back to normal*
if + rod and wire, e- from ground go into sphere
if using insulator, wouldn't flow but could five slight + charge on surface - 12—
- 13An electrically neutral object acquires a net electric charge. Which one of the following statements concerning the mass of the object is true?The mass increases if the charge is negative and decreases if it is positive.
Reasoning: A net electric charge indicates that electrons were either gained or lost. Since electrons are negatively charged, the mass increases if the charge is negative and decreases if it is positive. - 14Object A has a charge of -1.6 x 10-13 C, and object B is electrically neutral. Two million electrons are removed from object A and placed on object B. Expressed in coulombs, what is the resulting charge (algebraic sign and magnitude) on object A and on object B?
- 15A rod made from insulating material carries a net charge (which may be positive or negative), whereas a copper sphere is electrically neutral. The rod is held close to the sphere but does not touch it. Which one of the following statements concerning the forces that the rod and sphere exert on each other is true?The forces are always attractive.
Reasoning: The charged rod will attract charge of the opposite sign to the surface of the sphere. Thus, the rod and the sphere will always be attracted to each other - 16—C, A, B
- 17A Gaussian surface contains a single charge within it, and as a result an electric flux passes through the surface. Suppose that the charge is then moved to another spot within the Gaussian surface. Does the flux through the surface change?No, because the charge is still within the Gaussian surface.
- 18—since each encloses the same net charge, the same flux passes through each.
- 19—B, A, C
- 20Because of an electric field, a positive charge +q experiences a force of magnitude F that points due west. The positive charge is then replaced with a negative charge -2q. What force does the negative charge experience?Force magnitude = 2F, force direction is due east
The force on the negative charge points opposite to the field and, therefore, points due east. - 21—B, C, A
The electric field has a greater magnitude where the field lines are closer together
They are closest together at B and farthest apart at A. Therefore, the field has the greatest magnitude at B and the smallest magnitude at A.
- 22Electric field-is a vector
-farther away = less electric
- if the positive arrow points away, the arrow points towards negative
-N/C - 23Parallel plate capacitor-the conducting plates charge is equal but opposite (pos. vs neg.); so you use charge in one plate because if you use both they equal out to zero
-space in between is always an insulator, so the charges don't neutralize each other - 24ε0 nameepsilon naught
permittivity of free space - 25electric field lines-begin on + charge and end on - charge, do not stop midspace
-the # of lines leaving + or entering - charge is proportional to magnitude of charge (if 100 on 4µC three 75 on -3µC)
-field lines can't cross
-direction always tangent to the line (only touching one point, not tangent is like u shape graph horizontal touching two) - 26the electric field inside a conductor-at equilibrium under electrostatic conditions, any excess charge resides on the surface of the conductor; the electric field is 0 at any point within the material; the conductor sheilds any charge within it from electric fields created outside (no lines insides)
- 27Flux-Φ
-is scalar
-N m^2/C = 1 wb (weber)
-flux is proportional to the electric field lines that goes through the energy (higher lines, higher flux) **only contributes if they go THROUGH** - 28—
- 29—
- 30—
- 31Four point charges have the same magnitude of 2.4 × 10−12 C and are fixed to the corners of a square that is 4.0 cm on a side. Three of the charges are positive and one is negative. Determine the magnitude of the net electric field that exists at the center of the square.
- 32An electron is released from rest at the negative plate of a parallel plate capacitor. The charge per unit area on each plate is σ = 1.8 × 10−7 C/m2, and the plate separation is 1.5 × 10−2 m. How fast is the electron moving just before it reaches the positive plate?
- 33A spherical surface completely surrounds a collection of charges. Find the electric flux through the surface if the collection consists of (a) a single +3.5 × 10−6 C charge, (b) a single −2.3 × 10−6 C charge, and (c) both of the charges in (a) and (b).
- 34Area of sphere and cylindersphere: 4πr2
cylinder: 2πr(r+h) - 35Electric potential-scalar
-volt (V); J/C
-electric potential can be + or - (electric field only +)
-electric potential = potential = voltage - 36—
- 37Capacitors-energy stored in a capacitor; stores electrical energy un core
-C/V = farad F - 38A particle has a charge of +1.5 μC and moves from point A to point B, a distance of 0.20 m. The particle experiences a constant electric force, and its motion is along the line of action of the force. The difference between the particle's electric potential energy at A and at B is EPEA − EPEB = +9.0 × 10−4 J. (a) Find the magnitude and direction of the electric force that acts on the particle. (b) Find the magnitude and direction of the electric field that the particle experiences.
- 39—
- 40—
- 41—
- 42An empty parallel plate capacitor is connected between the terminals of a 9.0-V battery and charged up. The capacitor is then disconnected from the battery, and the spacing between the capacitor plates is doubled. As a result of this change, what is the new voltage between the plates of the capacitor?
- 43equipotential surface-a surface on which the electrical potential is the same everywhere
-the net electric force does no work on a charge as it moves on an equipotential surface because the force is always perpendicular to the displacement of the charge
-scalar, while electric fields are vector - 44dielectric-region between the plates is filled with this electrically insulating substance (insulator)
-air = insulator (ka = 1; ka is always greater than or equal to 1)
- 45Capacitancecoulomb/volt = farad (F)
-dielectric inserted between the plates of a capacitor inc. capacitance and dec. electric field plates
-capacitor to handle charges before it begins to repel charges (like water overflowing a bucket)
-proportional to area, inversely to distance - 46—
- 47—
- 48—
- 49—
- 50electric potential energy-Electric potential at a point in an electric field is the amount of work done to bring the unit positive charge from infinity to that point, while electric potential energy is the energy that is needed to move a charge against the electric field
-Joules
-scalar - 51electric field and electric forcewhen q is positive they have the same direction but opposite when negative
net force and acceleration always have the same direction - 52—The work is the same in all three cases
The work done by the electric force is equal to the change in the electric potential energy. Electric potential energy is equal to charge multiplied by electric potential. Since the change in the electric potential is the same in all three cases, the work done is the same in all three cases as well.
- 53A proton and an electron are released from rest at the midpoint between the plates of a charged parallel plate capacitor. Except for these particles, nothing else is between the plates. Ignore the attraction between the proton and the electron, and decide which particle strikes a capacitor plate first.the electron
Since the mass of the electron is less than the mass of the proton, the electron strikes one plate before the proton strikes the other. - 54—Since the electric potential is directly proportional to the charge and inversely proportional to the distance from the charge to the location where the potential is being determined, the total electric potentials at point P are as follows. For A and D, 0 V. For B, 3kq/2r. For C, kq/2r.
- 55Consider a spot that is located midway between two identical point charges. Which one of the following statements concerning the electric field and the electric potential at this spot is true? -The electric field is zero, but the electric potential is not zero. -Both the electric field and the electric potential are zero. -Neither the electric field nor the electric potential is zero. -The electric field is not zero, but the electric potential is zero.The electric field is zero, but the electric potential is not zero.
The electric field is a vector while the electric potential is a scalar. Since the two electric field vectors have the same magnitude, but opposite directions, their sum is zero. Since the two electric potentials are either both positive or both negative, their sum is not zero. - 56—A and C (a tie), B
The total electric potential at the origin is the algebraic sum of the potentials due to all the charges. Since each potential is of the form V = kq/r (Equation 19.6) and r is same for each charge, the total electric potential is proportional to the sum of the charges. The sum of the charges in A (+4q) equals the sum in C (+4q), which is greater than the sum in B (+2q)
- 57—VA > VB > VD > VC
- 58—zero volts
- 59The plates of an isolated parallel plate capacitor with a capacitance C carry a charge Q. What is the capacitance if the separation distance between the plates of the capacitor is increased to 2d? C/4 4C C 2C C/2C/2
- 60The plates of an isolated parallel plate capacitor with a capacitance C carry a charge Q. What is the capacitance of the capacitor if the charge is increased to 2Q? 4C C 2C C/4 C/2C
- 61A battery charges capacitor A until the potential difference between the two conductors of the capacitor is V. A second, identical capacitor, labeled B, is charged by another battery until the potential difference of capacitor B is 2V. How does the stored energy of capacitor B compare to that of capacitor A?The stored energy of capacitor B is four times that of capacitor A.
- 62A charge of +121 μC is fixed at the center of a square that is 0.66 m on a side. How much work is done by the electric force as a charge of +7.7 μC is moved from one corner of the square to any other empty corner?
- 63—
- 64Identical point charges of +1.6 μC are fixed to diagonally opposite corners of a square. A third charge is then fixed at the center of the square, such that it causes the potentials at the empty corners to change signs without changing magnitudes. Find the sign and magnitude of the third charge.
- 65—
- 66If the charge is outside the flux will be...0
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- Beschreibung
- College Physics II Karteikarten am Physics Exam 1, erstellt von Bree Bree am 14/01/2022.
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- Bree Bree
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