Chapter 26 - Capacitance and Dielectrics

What does a capacitor measure and what does it consist of

Measures: Capacitance, the ability to store electrical charge. Consists of: Two conductive plates separated by an insulating material, known as a dielectric.

Relationship between area and capacitance

As area increases, capacitance increases

Relationship between distance and capacitance

As distance increase, capacitance decreases

Relationship between dielectric constant k, capacitance, voltage and charge

As k increases, capacitance increase, voltage decrease, charge stays the same

Derive equation for capacitance of an isolated sphere

area = a, assume V=0 for infinitely large space .

Is the capacitance of an isolated sphere dependent on charge or the potential?

No, only on the area

Derive equation for cylindrical capacitor

Capacitance of spherical conductor

When does the flow of charges cease in a capacitor circuit?

The flow of charges ceases when the voltage across the capacitors equals that of the battery.

Potential difference across capacitors in parallel circuit

The potential difference across the capacitors is the same. Each is equal to the voltage of the battery.

ΔV1 = ΔV2 = ΔV.

When do capacitors reach their maximum charge?

when the flow of charge ceases

Qtotal in parallel circuit

The total charge is equal to the sum of the charges on the capacitors. Qtot = Q1 + Q2.

Equivalent capacitance in a parallel combination

Ceq = C1 + C2 + C3 + ...

Capacitor charges in a seriescombination

The charges are all the same. Q1 = Q2 = Q.

Voltage addition in a parallel combination

ΔVtot = ΔV1 + ΔV2 + …

Equivalent capacitance in a series combination

The equivalent capacitance is 1/Ceq = 1/C1 + 1/C2 + ...

The equivalent capacitance in a series combination of capacitors is _______ than any individual capacitor.

less

The potential differences across capacitors in series _______ up to the battery voltage.

add

What is the same across all capacitors in parallel circuit

Voltage

What is the same across all capacitors in series circuit

Charge

Work needed to transfer a charge from one plate to another

Work done for charging a capacitor

It is the electric potential energy U

Relationship between energy stored, charge and potential difference

The energy stored increases as the charge increases and as the potential difference increases

Energy for parallel-plate capacitor expressed in terms of field

Energy in terms of charge density

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Energy stored in a parallel-plate capacitor before inserting a dielectric

Energy stored in a parallel-plate capacitor after inserting a dielectric