Assignment IV Solutions - General Physics II | PHY 212, Assignments of Physics

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28.17. Visualize:

For any closed surface that encloses a total charge Q in

, the net electric flux through the closed surface is

e in 0

Φ = Q ε.

28.19. Visualize: Please refer to Figure EX28.19.

Solve: For any closed surface that encloses a total charge Q in , the net electric flux through the surface is

e in 0

Φ = Q ε.We can write three equations from the three closed surfaces in the figure:

1 3

A

0 0

q q q

ε ε

q

1

+ q

3

= − q

1 2

B

0 0

3 q q q

ε ε

q

1

+ q

2

= 3 q

2 3

C

0 0

2 q q q

ε ε

Φ = = ⇒ q

2

+ q

3

= − 2 q

Subtracting third equation from the first,

q

1

• q 2

= + q

Adding second equation to this equation,

2 q

1

= + 4 q ⇒ q

1

= 2 q

That is, q

1

= + 2 q , q

2

= + q , and q

3

= − 3 q.

28.28. Visualize: Please refer to Figure EX28.28.

Solve: For any closed surface that encloses a total charge Q in , the net electric flux through the closed surface is

e in 0

Φ = Q ε.In the present case, the conductor is neutral and there is a point charge Q inside the cavity. Thus

in

Q = Q and the flux is

e

0

Q