advertisement

Ch26-1. The solid line has length A and makes an angle with the negative y-axis. What is the length of the dotted line? y A: A cos B: A sin C: A tan D: sin/A E: cos/A x A Ch26-2. A 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? kQ A) d x B) kQ x2 d2 C) x 2 y Q d kQ 2 d2 2 x D) kQ x2 d2 E) None of these E Ch26-3. z The integral E dE means E z x dE x z y dE y z z dE x . 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 pointA shown, what can you can about the x- and y- components of E ? y A ++++++++++++++++++++++++++ x A: Ex = 0, Ey < 0 C: Ex = 0, Ey =+ E: Ex > 0, Ey > 0 B: Ex < 0, Ey = 0 D: Ex = 0, Ey > 0 Ch26-4. A circular ring of radius R, uniformly charged with total charge +Q, is in the xy plane centered on the origin. The electric field dE at position z = h on the z-axis, due to a small piece of the ring with charge dQ, is shown. What is the magnitude of the field dE? kQ A: 2 h z dE h k dQ B: h2 R k dQ C: 2 R h2 D: k dQ x y dQ R2 h2 E: None of these. What is dEz, the z-component of dE ? A: dE sin B: dE cos C: dE tan What is cos? h A: 2 R h2 h 1 D: cos 2 2 R h B: h R2 h2 E: None of these! D: None of these. C: h R Ch26-5. A circular ring uniformly charged with positive charge Q is in the xy plane centered on the origin as shown. On the z-axis, E E z z . Which graph accurately represents the electric field Ez on the z-axis? Ez Ez z A) y x z B) Ez Ez z C) z D) E: None of these is an accurate representation of Ez z Ch26-6. ˆ ? What the magnitude of the vector (iˆ ˆj) (xˆ y) A) 1 B) 2 C) 0 D) Some other number. ˆ is not a vector. E) No answer, because (xˆ y) Ch26-7. There are no charges near inside the regions shown. Which of the following are possible electric field line configurations? (b) (a) (c) A: (a) only B: (b) only C: (c) only D: None are possible E: Some other answer (all, a and b only, etc.) Ch26-8. Consider 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. I II III IV A: All are possible. D: None are possible. B: II only C: II and III only E: None of the above. Ch26-9. From the figure, what can you say about the magnitude of the charge on the bar Q bar , compared to the magnitude of the charge Q of the positive point charge? A: Q bar Q B: Q bar Q C: Q bar Q + Q Qbar From the figure, what can you say about the net charge on the bar? A: Qbar = 0 B: 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. B ++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++ A The field in region B has magnitude… A: zero B: E C: 2E D: depends on exact position. C The field in region A has magnitude… A: zero B: E C: 2E D: depends on exact position. Ch26-11. A dipole is placed in an external field as shown. In which situation(s) is the net force on the dipole zero? (1) (3) A: B: C: D: E: (1) (2) (1) and (2) (3) and (4) (2) and (4) (2) (4) Ch26-12. velocity V(t) +4m/s -4m/s time t 0 5 10 15 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 z tf v( t ) dt ti . The graph above shows v(t). What is the displacement after 10 seconds? A: 3m D: 18m B: 8m C: 10m E: None of these. Ch26-13. Areal mass density of a tile is mass m per area A: m A If a sheet has area A and uniform density , then its mass is m = A. If a sheet has a non-uniform density x, y , where (x,y) is the postion on the sheet, then the total mass of the sheet is bg m z da z d2r zzb g x, y dx dy where da = d2r represents an infinitesimal area element. Consider a square sheet in the x-y plane with edge length L and density b kx , where b and k are constants. Which expression below correctly represent the integral for the mass? L Green : L b kx dx L L2 b kx dx Yellow : 0 0 L Pink : kx dx L Blue : 0 Purple : None of these/ don't know. y L b kx dx 0 da’s L x