Conductors, Dielectrics and Capacitors

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

Tags

NGSS.HS-PS3-2

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.

Tags

NGSS.HS-PS3-5

An air-filled capacitor is charged, and then a dielectric is inserted. As a result, there is an induced charge on the dielectric. What is the difference between induced charge and free charge?

• There is no difference.
• Induced charge does not result in a net charge on the dielectric.
• Induced charge is smaller than free charge.
• Free charge creates an electric field, but induced charge does not.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

Which of the following is not a dielectric?

• silicon
• germanium
• polystyrene
• titanium

One of the materials listed below is to be placed between two identical metal sheets, with no air gap, to form a parallel-plate capacitor.  Which produces the greatest capacitance?

• material of thickness 0.5 mm and dielectric constant 11
• material of thickness 0.4 mm and dielectric constant 8
• material of thickness 0.3 mm and dielectric constant 2
• material of thickness 0.2 mm and dielectric constant 3

A battery is used to charge a parallel-plate capacitor, after which it is disconnected. Then the plates are pulled apart to twice their original separation. This process will double the: 

• capacitance 
• surface charge density on each plate 
• stored energy
• electric field between the two places 

Tags

NGSS.HS-PS3-5

A certain capacitor has a capacitance of 5.0 mF. After it is charged to 5 mC and isolated, the plates are brought closer together so its capacitance becomes 10 mF. The work done by the agent is about: 

• 0 J
• 1.25 ´ 10^–6 J 
• -1.25 ´ 10^–6 J 
• 8.3 ´ 10^–7 J 

Tags

NGSS.HS-PS3-1

A parallel-plate capacitor has a plate area of 0.30 m² and a plate separation of 0.10 mm. If the charge on each plate has a magnitude of 5.0 ´ 10^–6 C, what is the energy density in its electric field?

• 0.16 J/m³ 
• 3.5 J/m³ 
• 7.8 J/m³
• 16 J/m³

Tags

NGSS.HS-PS3-2

To store a total of 0.040 J of energy in the two identical capacitors shown, each should have a capacitance of: 

• 0.50 microF 
• 1.0 microF
• 1.5 microF
• 2.0 microF

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-5