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Review for the Chapter 16-17 test Page 1 Page 2 Page 3 Page 4

Review for the Chapter 16-17 test Page 1 Page 2 Page 3 Page 4. Page 1 These examples all have to do with electric field – the question on the test has to do with gravity, but parallels these questions. Best also look at the suggested review questions on the Field Theory worksheet. toc.

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Review for the Chapter 16-17 test Page 1 Page 2 Page 3 Page 4

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  1. Review for the Chapter 16-17 test Page 1 Page 2 Page 3 Page 4

  2. Page 1 These examples all have to do with electric field – the question on the test has to do with gravity, but parallels these questions. Best also look at the suggested review questions on the Field Theory worksheet toc

  3. Vesta Buhl measures an electric field of 2,120 N/C, 67 cm from a charge of unknown value. The electric field is away from the charge. What is the charge? • E for a point charge: • E = kq • r2 • k = 8.99x109 Nm2C-2, E = 2,120 N/C, r = .67 m • q = 1.06x10-7 C = +.11 C. It is a positive charge as the E-field is away from it W +.11 C

  4. Electric Field Example 2 - An electron travels through a region where there is a downward electric field of 325 N/C. What force in what direction acts on the electron, and what is its acceleration? F = Eq = (325 N/C)(1.602x10-19 C) = 5.21x10-17 N up F = ma, a = F/m = (5.21x10-17 N)/(9.11x10-31kg) = 5.72x1013 m/s/s TOC

  5. Jess Uwaite places a +3.0 mC charge 3.5 m from a +5.0 mC charge. What is the force of repulsion? (1 mC = 10-3 C) • F = kq1q2 • r2 • k = 8.99x109 Nm2C-2, q1 = 3.0x10-3 C, q2 = 5.0 x10-3 C, • r = 3.5 m • F = 11,000 N W 11,000 N

  6. Noah Verkreinatlaad places a 5.0 C charge how far from a 3.0 C charge to make the force between them exactly 4.00 N? • F = kq1q2 • r2 • k = 8.99x109 Nm2C-2, q1 = 5.0 C, q2 = 3.0C, F = 4.0 N • r = 1.8x105 m = 180 km = 100 miles wow W 180 km

  7. A B -180 C +120 C 70. cm 170 cm x What is the electric field at the x? Which Direction is it? • EA = kqA = 2201632.653 N/C (to the right) • r2 • EB = kqB = 559930.7958 N/C (to the right) • r2 • = 2201632.653 N/C right + 559930.7958 N/Cright = 2761563.449 N/C right = 2.7E6 N/C right W 41 N left

  8. Try this one q q q What work to bring a 13.0 C charge from halfway between the other two charges to 6.0 cm from the positive and 18 cm from the negative? +3.20 C +13.0 C -4.10 C 12.0 cm 12.0 cm Initial V -67425 V Final V 274700. V Change in V 342100. V Work 4.448 V TOC +4.4 J

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  10. Lee DerHosen places a voltage of 25 V across two || plates separated by 5.0 cm of distance. What is the electric field generated? E = V/d, V = 25, d = .050 m E = 500 V/m = 5.0x102 V/m W 5.0x102 V/m

  11. Electric Field Direction: Force This Way +Q E Force This Way -Q Example 1 - A +125 C charge experiences a force to the right of .0175 N. What is the Electric field, and its direction? E = F/q = .0175 N/125x10-6 C = 140 N/C to the right TOC

  12. Which way is the electric field? (wwpcd?) + + + + + - - - - -

  13. Sandy Deck does 125 J of work on a 12.5 C charge. Through what voltage did she move it? V = W/q, W = 125 J, q = 12.5 C V = 10.0 V W 10.0V

  14. Brennan Dondahaus accelerates an electron (m = 9.11x10-31 kg) through a voltage of 1.50 V. What is its final speed assuming it started from rest? V = W/q, W = Vq = 1/2mv2 V = 1.50 V, m = 9.11x10-31 kg, q = 1.602x10-19 C v = 726327.8464 = 726,000 m/s W 726,000 m/s

  15. Alex Tudance measures a voltage of 25,000 volts near a Van de Graaff generator whose dome is 7.8 cm in radius. What is the charge on the dome? V = kq/r, r = .078 m, V = 25,000 V q = 2.17x10-7 C = .22 C W .22 C

  16. Cute problems with voltage Q Q What work to bring a 6 C charge from infinity to halfway between the other two charges? +1.5 C +1.5 C 24.0 cm • Find initial voltage = 0 (at infinity) • Find final voltage = k(1.5E-6)/.12 + k(1.5E-6)/.12 = 224750 V • V = 224750 V - 0 = 224750 V • W = Vq = (224750 J/C)(6E-6C) = 1.3485 J TOC

  17. Try this one Q Q Q What work to bring a 13.0 C charge from halfway between the other two charges to 6.0 cm from the positive and 18 cm from the negative? +3.20 C +13.0 C -4.10 C 12.0 cm 12.0 cm Initial V -67425 V {k(3.2E-6)/.12 + k(-4.10E-6)/.12} k = 8.99E9 Final V 274700. V {k(3.2E-6)/.06 + k(-4.10E-6)/.18} Change in V 342100. V {Final - initial} Work 4.448 V {W = Vq, q = +13.0 C - the moved charge} TOC +4.4 J

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  19. 45.0 cm me = 9.11 x 10-31 kg 20.0 cm An electron traveling 114,700 m/s parallel to the plates above, and midway between them is deflected upward by a potential of .0120 V. A. What is the electric field between the plates? E = V/d, V = .0120 V, d = .200 m E = .0600 V/m W .0600 V/m

  20. 45.0 cm me = 9.11 x 10-31 kg 20.0 cm An electron traveling 114,700 m/s parallel to the plates above, and midway between them is deflected upward by a potential of .0120 V. B. What is the electrical force on the electron between the plates? E = F/q, E = .0600 V/m, q = -1.602x10-19 C F = 9.6120x10-21 N = 9.61x10-21 N W 9.61x10-21 N

  21. 45.0 cm me = 9.11 x 10-31 kg 20.0 cm An electron traveling 114,700 m/s parallel to the plates above, and midway between them is deflected upward by a potential of .0120 V. C. What is the upward acceleration of the electron between the plates? F = ma, F = 9.6120x10-21 N, m = 9.11x10-31 kg a = 1.0551x1010 m/s/s = 1.06x1010 m/s/s (You can neglect gravity) W 1.06x1010 m/s/s

  22. 45.0 cm me = 9.11 x 10-31 kg 20.0 cm An electron traveling 114,700 m/s parallel to the plates above, and midway between them is deflected upward by a potential of .0120 V. D. For what time is the electron between the plates? V = s/t, V = 114,700, s = .45 m t = 3.9233x10-6 s = 3.92x10-6 s W 3.92x10-6 s

  23. 45.0 cm me = 9.11 x 10-31 kg 20.0 cm An electron traveling 114,700 m/s parallel to the plates above, and midway between them is deflected upward by a potential of .0120 V. E. What is the vertical displacement of the electron while is passes between the plates? s = ut + 1/2at2, u = 0, t = 3.9233x10-6 s, a = 1.0551x1010 m/s/s s = .0812 m = 8.12 cm W 8.12 cm

  24. 45.0 cm me = 9.11 x 10-31 kg 20.0 cm An electron traveling 114,700 m/s parallel to the plates above, and midway between them is deflected upward by a potential of .0120 V. F. Through what potential was the electron accelerated to reach a velocity of 114,700 m/s from rest? Vq = 1/2mv2, q = 1.602x10-19 C, v = 114,700, m = 9.11x10-31 kg V = .0374 V W .0374 V

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  26. A B -180 C +120 C 70. cm 170 cm x What is the electric field at the x? Which Direction is it? • EA = kqA = 2201632.653 N/C (to the right) • r2 • EB = kqB = 559930.7958 N/C (to the right) • r2 • = 2201632.653 N/C right + 559930.7958 N/Cright = 2761563.449 N/C right = 2.7E6 N/C right W 41 N left

  27. A B C Find the force on C, and the angle it makes with the horizontal. (the one on the test is electric field…) +180 C .92 m +520 C +150 C 1.9 m FAC= 286.8 N, FBC = 188.8 N ABC = Tan-1(.92/1.9) = 25.84o FAC = 0 N x + 286.8 N y FBC = -188.8cos(25.84o) x + 188.8sin(25.84o)y Ftotal = -170. x + 369 y W 410 N, 65o above x axis (to the left of y)

  28. Q2 Q1 + 2.6x104 V And The Sum Is… A Find the voltage at point A: +1.5 C +3.1 C 75 cm 190 cm • Voltage at A is scalar sum of V1 and V2: • Voltage due to Q1: • V1 = kq1 = k(1.5x10-6) = 1.27x104 V • r (.752+.752) • Voltage due to Q2: • V2 = kq2 = k(3.1x10-6) = 1.36x104 V • r (.752+1.92) TOC

  29. Q2 Q1 Find the voltage at point C C -4.1 C 38 cm 85 cm +1.1 C V1 = -39587.58847 V2 = +26023.68421 V1 + V1 = -13563.90426 = -14,000 V W -14,000 V

  30. Cute problems with voltage Q Q What work to bring a 6 C charge from infinity to halfway between the other two charges? +1.5 C +1.5 C 24.0 cm • Find initial voltage = 0 (at infinity) • Find final voltage = k(1.5E-6)/.12 + k(1.5E-6)/.12 = 224750 V • V = 224750 V - 0 = 224750 V • W = Vq = (224750 J/C)(6E-6C) = 1.3485 J TOC

  31. Try this one Q Q Q What work to bring a 13.0 C charge from halfway between the other two charges to 6.0 cm from the positive and 18 cm from the negative? +3.20 C +13.0 C -4.10 C 12.0 cm 12.0 cm Initial V -67425 V {k(3.2E-6)/.12 + k(-4.10E-6)/.12} k = 8.99E9 Final V 274700. V {k(3.2E-6)/.06 + k(-4.10E-6)/.18} Change in V 342100. V {Final - initial} Work 4.448 V {W = Vq, q = +13.0 C - the moved charge} TOC +4.4 J

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