Lecture Notes 2P10 – Capacitors Flashcards

Flashcards based on lecture notes about capacitors.

What is a capacitor?

A component which can store electrical energy.

What does a capacitor consist of?

Two conducting plates separated by an insulator.

Give examples of materials used as dielectrics in capacitors.

Air, ceramic material, or paper.

How does a capacitor store electrical energy?

Distributing electric charge on the two plates to create a potential difference.

When does current flow stop when charging a capacitor?

The potential difference across the plates becomes equal to the potential difference of the battery.

What happens when the potential difference across a capacitor is reduced to zero?

The capacitor is fully discharged.

In the charge vs. potential difference graph, what does it mean if capacitor X has more charge at a particular voltage compared to capacitor Y?

X has a higher capacitance.

What is the formula relating charge (Q), capacitance (C), and voltage (V)?

Q = C.V

What unit is capacitance measured in?

Farads (F).

If there are 6.0 x 10^12 excess electrons on the plate of a capacitor, and there is a potential difference of 5.0 V between the plates, what is the capacitance of the capacitor? (e = 1.6 x 10^-19 C)

C = Q/V = (6.0 x 10^12 x 1.6 x 10^-19) / 5.0 = 1.92 x 10^-7 F (192 nF)

What is the formula for the capacitance of a parallel plate capacitor?

C = ε.A / d.

In the parallel plate capacitor formula, what does 'A' represent?

Area of each plate (m^2).

In the parallel plate capacitor formula, what does 'd' represent?

Separation of the plates (m).

In the parallel plate capacitor formula, what does 'ε' represent?

Permittivity of the dielectric (F m^-1).

What is relative permittivity (dielectric constant)?

The ratio of the permittivity of a substance to the permittivity of free space.

What is the equation that relates permittivity, relative permittivity, and the permittivity of free space?

ε = εr . ε0

What type of energy is stored in a capacitor?

The electric potential energy.

What is the formula for the energy stored in a capacitor?

E = ½C.V^2

What is the formula for the time constant (τ) in a CR circuit?

τ = R.C

What does the time constant (τ) represent in a CR circuit?

The time taken for the voltage to fall to 37% of its original value.