Capacitors

If the charge on a parallel-plate capacitor is doubled:

• the capacitance is halved 
• the capacitance is doubled 
• the electric field is halved 
• the electric field is doubled

The capacitance of a parallel-plate capacitor is: 

• proportional to the plate area 
• proportional to the charge stored 
• independent of any material inserted between the plates 
• proportional to the potential difference of the plates 

The capacitance of a parallel-plate capacitor can be increased by: 

• increasing the charge 
• decreasing the charge 
• increasing the plate separation
• decreasing the plate separation 

If both the plate area and the plate separation of a parallel-plate capacitor are doubled, the capacitance is: 

• doubled
• halved
• unchanged 
• one-fourth the original 

A parallel-plate capacitor has a plate area of 0.2 m² and a plate separation of 0.1 mm. To obtain an electric field of 2.0 ´ 10⁶ V/m between the plates, the magnitude of the charge on each plate should be:

• 3.5 ´ 10^-6 C
• 7.1 ´ 10^-6 C 
• 1.4 ´ 10^-5 C
• 1.8 ´ 10^-5 C

An air-filled parallel-plate capacitor has a capacitance of 1 pF. The plate separation is then doubled and a wax dielectric is inserted, completely filling the space between the plates. As a result, the capacitance becomes 2 pF. The dielectric constant of the wax is: 

• 0.25 
• 0.50 
• 2.0
• 4.0

A dielectric slab is slowly inserted between the plates of a parallel plate capacitor while the capacitor is connected to a battery.  As it is being inserted:

• the capacitance and the charge on the plate increase but the potential difference between the plates remains the same
• the capacitance and the charge on the positive plate decrease but the potential difference between the plates remains the same
• the potential difference between the plates increases, the charge on the positive plate decreases, and the capacitance remains the same
• the capacitance, the potential difference between the plates, the charge on the positive plate all decrease

What happens to the atoms in a dielectric when it is placed between the plates of a charged capacitor?

• They begin to conduct electricity.
• They create an induced electric field that is in the opposite direction of the field due to the charges on the plates.
• They create an induced electric field that is in the same direction as the field due to the charges on the plates.
• They completely cancel the electric field due to the charges on the plates.

Which of the following is not a dielectric?

• silicon
• germanium
• polystyrene
• titanium

What is the symbol for dielectric permeativity.

• ε
• ε_r
• ε₀
• ε_rε₀