How does a capacitor work?
Parallel plates (usually have an insulator between them) with electrons on one side and a positive charge on the other side. This build up of electrons stores energy from the battery.
What kind of curve is a discharging capacitor for charge and voltage?
Exponential decay.
Define capacitance.
Charge stored per unit p.d.
Measured in farads (F).
What kind of curve is a charging capacitor for charge and voltage?
Exponential growth.
What is the time constant?
Resistance x Capacitance
What is the formula to find the half-life of a capacitor given the time constant?
Half-life = ln2 x time constant
For a charging capacitor in series with a resistor:
What is the charge and voltage of the capacitor and resistor at t=0?
Charge and voltage of capacitor = 0
Charge and voltage of resistor = maximum.
For a charging capacitor in series with a resistor:
What is the charge and voltage of the capacitor and resistor at t»0?
Charge and voltage of capacitor = maximum.
Charge and voltage of resistor = 0
How do you change the voltage of a capacitor if it is disconnected from the battery?
Varying the distance between plates.
How do you keep the current constant on a charging capacitor?
Use a variable resistor in the circuit.
What is meant by the permittivity of a material?
How difficult it is to generate an electric field in the material.
What are polar molecules in capacitors?
Molecules with a positive and negative end. Their electric field interacts with capacitor so it can gain charge for lower voltages (opposes applied electric field).
What is a dielectric?
Insulating material between capacitors that improves voltage / energy storing properties without allowing current to flow across plates.
What is the anti-parallel position for polar molecules?
Rotate so the negative end lines up with the positive plate.
