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Flashcards in Capacitors ! Deck (9)
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1

Potential difference - time graph.
How does it change with resistance?
Describe for chartering and discharging capacitors.

The greater the resistance the longer the capacitor will take to (fully) charge or discharge.
Charging:
The smaller the resistance the more ‘cornery’ the curve will be where the corner will be closer to max p.d.
Discharging:
The smaller the resistance the steeper the curve becomes, the closer it gets to the origin.
Or the greater the resistance the more of a straight negative line it becomes.

2

Explain how a discharging p.d - time curve has a constant-ratio property (exponential decay).

V decreases to 0.37 of its initial value after the time constant.

3

Define the time constant of a capacitor-resistor discharge circuit.

The time constant for the p.d/ current/ charge decreases to 1/e (0.37) of its initial value.

4

Capacitance is measured in farads. Define the farad.

Farad = 1 coulomb per unit volt.

5

Voltage against Charge.
What is the gradient.
What is the area under graph.

Gradient = 1/C
Area = Work done, Energy

6

Define capacitance.

Capacitance = Charge / (per unit) Potential Difference.

7

Describe and explain in terms of the movement of electrons how the potential difference across the capacitor changes.
(EXPLAIN)

Electrons move in (anti)clockwise motion. (- to +)
Charge on plates decrease/ electrons neutralise positive charge.
p.d. Decreases exponentially

8

A capacitor is discharging.
The capacitor is in series with a resistor.
Where does the initial energy stored in the capacitor is dissipate to?

It dissipates as heat in the resistor and wire.

9

Explain in terms of movement of electrons how the capacitor plates acquire an equal but opposite charge.
(EXPLAIN)

State direction of electrons.
Electrons deposited on X removed from Y.
An equal number of electrons removed and deposited on plates.