Question

PART A 

What property of objects is best measured by their capacitance?

a)ability to conduct electric current

b)ability to distort an external electrostatic field

c)ability to store charge

 

Part B

Assume that charge ?q is placed on the top plate, and +q is placed on the bottom plate. What is the magnitude of the electric field E between the plates?

Express E in terms of q and other quantities given in the introduction, in addition to ?0 and any other constants needed.

E=

 

Part C

What is the voltage V between the plates of the capacitor?

Express V in terms of the quantities given in the introduction and any required physical constants.

 

Part D

Now find the capacitance C of the parallel-plate capacitor.

Express C in terms of quantities given in the introduction and constants like ?0.

 

Part E

Consider an air-filled charged capacitor. How can its capacitance be increased?

• Increase the charge on the capacitor.
• Decrease the charge on the capacitor.
• Increase the spacing between the plates of the capacitor.
• Decrease the spacing between the plates of the capacitor.
• Increase the length of the wires leading to the capacitor plates.

 

Part F

Consider a charged parallel-plate capacitor. Which combination of changes would quadruple its capacitance?

• Double the charge and double the plate area.
• Double the charge and double the plate separation.
• Halve the charge and double the plate separation.
• Halve the charge and double the plate area.
• Halve the plate separation; double the plate area.
• Double the plate separation; halve the plate area.

 

Answer 1

PartA; c) ability to store charge.

Part B);\(E=Q / \epsilon_{0} A\) ; where A is the area of the plates.

Part C; V = E / d.

Part D; \(\mathrm{C}=\epsilon_{0} \mathrm{~A} / \mathrm{d}\).

Part E; decrease the spacing between the plates of the capacitor.

Part F; halve the plate separation ; double the plate area.