1. $i_C>i_B>i_A>i_D$. The electron current is proportional to $r^2{v}_{\text{D}}$ Changing r by a factor of 2 has more influence than changing $v_{\text{D}}$ by a factor of 2.

2. The electrons don’t have to move from the switch to the bulb, which could take hours. Because the wire between the switch and the bulb is already full of electrons, a flow of electrons from the switch into the wire immediately causes electrons to flow from the other end of the wire into the lightbulb. 

3. $E_{\text{D}}>E_{\text{B}}>E_{\text{E}}>E_{\text{A}}=E_{\text{C}}$. The electric field strength depends on the difference in the charge on the two wires. The electric fields of the rings in A and C are opposed to each other, so the net field is zero. The rings in D have the largest charge difference.

4. 1 A into the junction. The total current entering the junction must equal the total current leaving the junction.

5. $J_B>J_A=J_D>J_C$. The current density $J=I/\pi r^2$ is independent of the conductivity $\sigma$, so A and D are the same. Changing r by a factor of 2 has more influence than changing I by a factor of 2.

6. $I_1=I_2=I_3=I_4$. Conservation of charge requires $I_1=I_2$. The current in each wire is $I=\text{Δ}{V}_{\text{wire}}/R$. All the wires have the same resistance because they are identical, and they all have the same potential difference because each is connected directly to the battery, which is a source of potential.

1. 3.0 d

3. $7\times {10}^{26}\text{electrons}$

5.

1. $4.6\times {10}^{21}\text{electrons}$

2. $4.3\times {10}^{-12}\text{m}$

7. 0.023 V/m

9.

1. $1.7\times {10}^7\text{A}\text{/}{\text{m}}^2$

2. $5.3\times {10}^{18}\text{s}{}^{-1}$

11. 130 C

13. $1.8\mu \text{A}$

15. $4.2\times {10}^6\text{A}\text{/}{\text{m}}^2$

17. 1.7 A

19. 0.16 V/M

21. $5.0\times {10}^{-8}\text{Ω}\text{m}$

23. $1.7\times {10}^{-5}\text{V}\text{/}\text{m}$

25.

1. 0.50

2. $3.5\text{Ω}$

27. Silver

29. 1.5 mV

31. 2.3 mA

33. 0.87 V

35. $50\text{Ω}$

37. 380

39. $6.2\times {10}^6$

41.

1. $3.1\times {10}^{14}$

2. $4.0\times {10}^2\text{A}\text{/}{\text{m}}^2$

3. $9.1\times {10}^5\text{V}\text{/}\text{m}$

4. 0.23 W

43.

1. 75 nA

2. 130 s

45. Yes, $2.2\times {10}^5{\text{Ω}}^{-1}{\text{m}}^{-1}$

47. $6.1\times {10}^{10}{\text{Ω}}^{-1}\text{m}{}^{-1}$, 1000 times greater

49. $71\text{°}\text{C}$

51. 100 V

53.

1. $\text{Δ}V=IR\Rightarrow \text{Δ}V=I/G$

2. $5.9{\text{Ω}}^{-1}$

3. 0.25 V

55. 0.60 kA

57.

1. ${\displaystyle \frac{\left(\text{Δ}V\right)A[1-\alpha (T-T_0)]}{{\rho }_{0}L}}$

2. 4.4 A

3. $-0.017\text{A}\text{/}\text{°}\text{C}$

59.

• a. ${\displaystyle \frac{1}{4\pi \sigma r^2}}$

• b. $E_{\text{inner}}=3.3\times {10}^{-4}\text{V/m, }{E}_{\text{outer}}=5.3\times {10}^{-5}\text{V}\text{/}\text{m}$

• c.

  

  Full Alternative Text

61. $1.01\times {10}^{23}$

63.

1. 2.0 A

2. $5.0\times {10}^{-5}\text{m}\text{/}\text{s}$

65.

1. 2.5 C

2. 1.8 cm

67. 36 A

69. $1.80\times {10}^3\text{C}$

71. 4R

73. ${\displaystyle \frac{3}{2}}{\displaystyle \frac{I}{\pi R^3}}$

75. 1.0 s