APPC Capacitance

Capacitors
Definition, Energy, Use

By Kathy Dao

Draw

Draw a parallel plate capacitor

Give basic formula of a Capacitor, and its units

Multiple Choice

Capacitance is measured in___________

• Coulombs

• Farads

• Hz

• Volts

Multiple Choice

What happens to the charge in a capacitor during the charging process?

• Collects more and more electrons

• Decreases charge over time

• Remains the same

Multiple Choice

The amount of charge that a capacitor can accept is determined by 

• It's capacity C=Q/V
• the plate area
• the dielectric thickness
• all of the above

1) Parallel Plate Capacitator
2) Conducting Sphere
3) Concentric Cylinders

​

​Derive Capacitance

Multiple Choice

The capacity of a parallel plate condenser is C . Its capacity when the separation between the plates is halved will be

• 4C

• 2C

• C/2

• C/4

Multiple Choice

A parallel plate capacitor is connected to a cell of constant emf. The plates are moved further apart without disconnecting the cell. What happens to the capacitance and voltage across the plates?

• capacitance increases; voltage remains constant
• capacitance remains constant; voltage decreases
• capacitance decreases; voltage increases
• capcitance decreases; voltage remains constant

Draw

Derive formula for total capacitor in a SERIES circuit.

Hint: Draw a capacitor connected in series and ask yourself which one (Q or V) is the same.

Multiple Choice

What formula does the above formula represent?

• Parallel capacitance

• Series resistance

• Parallel resistance

• Series capacitance

Multiple Choice

What formula does the above formula represent?

• Parallel capacitance

• Series resistance

• Parallel resistance

• Series capacitance

Draw

Derive formula for total capacitor in a PARALLEL circuit.

Hint: Draw a capacitor connected in parallel and ask yourself which one (Q or V) is the same.

Multiple Choice

A 5uF, a 10uF and a 20uF capacitor are connected in PARALLEL to a 6V battery. Calculate the total equivalent capacitance of the circuit?

• 35uF

• 0,35uF

• 2,857uF

• 0,0286uF

Multiple Choice

A 5uF, a 10uF and a 20uF capacitor are connected in SERIES to a 6V battery. Calculate the total equivalent capacitance of the circuit?

• 35uF

• 0,35uF

• 2,857uF

• 0,0286uF

1) Dielectric: insulating material

​2) Dielectric creates its own electric field that opposes the E-field of the capacitor
3) Capacitance is increased
4) κ: Dielectric constant; usually greater than 2

Capacitance with a Dielectric

Multiple Select

What are the factors that influence capacitance of a capacitor?

• Surface area

• Temperature

• Dielectric

• Length

• Distance between plates

1) Draw electric field of dielectric.
2) Prove that C increases when Q and V changes

​

​Derive Capacitance with dielectric

1) Formula for energy stored

​Energy Stored

Multiple Choice

Which graph would best represent the relationship between voltage and energy stored in a capacitor?

• A

• B

• C

• D

Multiple Choice

A capacitor stores an energy of 10J. If its area is doubled and the distance between its plates is cut in half, what would the new stored energy be?

• 2.5 J

• 5 J

• 20 J

• 40 J