23 Capacitors Flashcards
What is a capacitor?
An electrical device designed to store charge.
It consists of two parallel metal plates placed near each other
How does a capacitor work?
When the two metal plates are connected to a battery electrons move through the battery and are forced from the negative terminal on the battery to one of the plates.
An equal number of electrons leave the other plate and return the battery by the positive terminal.
What is capacitance C?
The charge stored per unit pd
What is the formula for C?
C=Q/V
What is the formula for energy stored by capacitor?
E=1/2 QV
What happens to 50% of the energy given to a capacitor?
50% is wasted due to resistance in the circuit as it is transferred to the surroundings when the charge flows in circuit
What is the time constant of a capacitor?
The time for a quantity that decreases exponentially to decrease to 0.37 of its initial value.
How does the charge of a capacitor vary with time? (discharging)
It decreases exponentially
How does potential difference/charge vary with time?(charging)
It is 1 - exponential
How does current vary with time? (Charging)
It decreases exponentially
What is a dielectric?
A material that increases the capacity of a parallel plate capacitor to store charge when placed between the plates of the capacitor
What is relative permittivity?
The ratio of the charge stored by parallel plate capacitor with dielectric filling the space between its plates to the charge stored without the dielectric for the same pd.
