Capacitors Flashcards
The normal decay formula for V tells you it across the
Capacitor as it’s discharging
How does the potential difference across a capacitor change as it charges up?
Increases at a decreasing rate
Define the constant-ratio property
A set change in time will always correspond to an decrease in charge in the same factor
The decay equation (1-e) for V, Q, A tells you it across
The capacitor as it is charging up
What is the time constant?
The time taken for a capacitor’s charge to fall by 63% or to charge to 63%
Which 3 factors affect capacitance and how?
Area of conducting plates: C proportional to A
Separation of plates: C inversely proportional to d
Properties of insulator between plates
How can you minimise uncertainty in equipment?
Use higher resolution equipment
What is a capacitor?
2 parallel electrodes that store charge, separated by an air gap or insulator
What is conductance?
Reciprocal of resistance, measured in siemons, Si
What is a galvanometer?
A sensitive ammeter
How is charge shared in series across capacitors?
Charge is the same as current is the same
How is charge shared in parallel across capacitors?
Charge adds up because current is shared
How does total capacitance add up?
Like spring constants.
What is capacitance?
The amount of charge per unit voltage stored by a capacitor
How to find charge of capacitor from graph?
Plot current against time and area under graph equals charge
