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