Ch21_2 - 1The solid line has length A and makes an angle with the negativey-axis. What is the length of the dotted line?A: A cosB: A sinC: A tanD: sin/AE: cos/ACh21_2 - 2A charge Q is on the y-axis at y = d. What is the magnitude of the E-field at position x, on the y-axis?A) ( )2kQd x+B) 2 2kQx d+C) ( )22 2kQx d+D) 2 2kQx d+E) None of thesex y A yQxdECh21_2 - 3The integral E dEz means E x dE y dE z dEx y x z z z .Often, from symmetry, one can see that one or more of the three component integrals vanishes.An infinite line of charge with linear charge density is along the x-axis and extends to . At the point A shown, what can you can about the x- and y- components of E?A: Ex = 0, Ey < 0 B: Ex < 0, Ey = 0C: Ex = 0, Ey =+ D: Ex = 0, Ey > 0E: Ex > 0, Ey > 0x y + + + + + + + + + + + + + + + + + + + + + + + + + + ACh21_2 - 4A circular ring of radius R, uniformly chargedwith total charge +Q, is in the xy plane centeredon the origin. The electric field dEur at position z= h on the z-axis, due to a small piece of the ringwith charge dQ, is shown. What is themagnitude of the field dE?A: 2kQhB: 2k dQhC: 2 2k dQR hD: 2 2k dQR hE: None of these.What is dEz, the z-component of dEur?A: dE sin B: dE cos C: dE tan D: None of these.What is cos?A: 2 2hR hB: 2 2hR hC: hRD: 12 2hcosR h E: None of these!y x z R dE dQ hCh21_2 - 5A circular ring uniformly charged with positivecharge Q is in the xy plane centered on theorigin as shown. On the z-axis, E E zz.Which graph accurately represents the electricfield Ez on the z-axis?E: None of these is an accurate representation of EzEzzEzzEzzEzzA)B)C)D)y x zCh21_2 - 6What the magnitude of the vector ˆ ˆˆ ˆ(i j) (x y)- = -?A) 1 B) 2 C) 0 D) Some other number.E) No answer, because ˆ ˆ(x y)- is not a vector.Ch21_2 - 7There are no charges near inside the regions shown. Which of the following are possible electric field line configurations?A: (a) onlyB: (b) onlyC: (c) onlyD: None are possibleE: Some other answer(all, a and b only, etc.)(a) (b) (c)Ch21_2 - 8Consider the four electric field line patterns shown. Assume that that are no charges in the regions shown. Which, if any, of the patterns represent possible electrostatic fields.A: All are possible. B: II only C: II and III onlyD: None are possible. E: None of the above.I IIIII IVCh21_2 - 9From the figure, what can you sayabout the magnitude of the chargeon the bar Qbar, compared to themagnitude of the charge Q of thepositive point charge?A: Q QbarB: Q QbarC: Q QbarFrom the figure, what can you sayabout the net charge on the bar?A: Qbar = 0B: Qbar > 0 (that is, the bar has a net positive charge)C: Qbar < 0 (the bar has a net negative charge)D: Not enough information in the figure to answer the question.Ch26-10 Two infinite planes are uniformly charged with the same charge per area . If one plane only were present, the field due to the one plane would be E. The field in region B has magnitude…A: zero B: E C: 2ED: depends on exact position.The field in region A has magnitude…A: zero B: E C: 2ED: depends on exact position.+ + Q Qbar ++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++ A B CCh21_2 - 11 A dipole is placed in an external field as shown. In which situation(s) is the net force on the dipole zero?A: (1) B: (2)C: (1) and (2)D: (3) and (4)E: (2) and (4) (1)(2)(3)(4)Ch21_2 - 12time t velocity V(t) 0 5 10 -4m/s 15 +4m/s For 1D motion, if velocity v is constant, then the displacement in time t is d = v t. If v is not constant, then the displacement is d v t dtttifz( ). The graph above shows v(t). What is the displacement after 10 seconds?A: 3m B: 8m C: 10mD: 18m E: None of these.Ch21_2 - 13Areal mass density of a tile is mass m per area A: mAIf a sheet has area A and uniform density , then its mass is m = A. If a sheet has a non-uniform density x y,b g, where (x,y) is the postion on the sheet, then the total mass of the sheet ism da d r x y dx dy zz zz 2,bgwhere da = d2r represents an infinitesimal area element.Consider a square sheet in the x-y plane with edge length Land density b kx, where b and k are constants.Which expression below correctly represent the integral forthe mass? L L20 0L L0 0Green : L b kx dx Yellow : L b kx dxPink : kx dx Blue : b kx dxPurple : None of these/ don't know. x y L L
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