M6C1 Flashcards
Define capacitor
A capacitor is a circuit component that stores energy by separating charges onto two electrical conductors with an insulator between them
Define capacitance
The capacitance of a capacitor is defined as the quantity of charge which can be stored per unit potential difference across the plates of the capacitor
What is the unit of capacitance?
The unit of capacitance is the farad, F. One farad is equivalent to one coulomb per volt
What is the capacitance equation?
C = Q/V C = capacitance (F) Q = charge (C) V = potential difference (V)
On a Q-V graph what is the gradient equal to?
The gradient is equal to the capacitance
On a Q-V graph what’s the area under the graph equal to?
The area under the graph is equal to the energy stored by the capacitor
A capacitor has a capacitance of 10 F. It is connected to a 10 V cell. Calculate the charge stored on the plates.
Q = CV = 10 x 10 = 100 C
What is the equation for total capacitance of capacitors in parallel?
Ct = C1 + C2 + ... Ct = total capacitance Cx = capacitance x
Whats is the equation for total capacitance of capacitors in series?
1/CT = 1/C1 + 1/C2 + ... Ct = total capacitance Cx = capacitance x
What are the equations for energy stored on a capacitor?
W = 1/2QV W = 1/2Q^2/C W = 1/2 v^2 C W = energy stored on the capacitor (J) Q = charge stored by the capacitor(C) V = P.D. across the capacitor(V) C = capacitance of the capacitor(f)
What is the time constant equation?
τ = CR τ = time constant (s) C = capacitance (C) R = resistance (Ω)
What’s the equation for discharging a capacitor?
X = Xo e^-t/τ X = current, charge or potential difference (A, C or V) Xo = initial or maximum current, charge or p.d. (A, C or V) t = time (s) τ = time constant (s)
What’s the equation for charging a capacitor?
X = Xo(1-e^-t/τ) X = current, charge or potential difference (A, C or V) Xo = initial or maximum current, charge or p.d. (A, C or V) t = time (s) τ = time constant (s)
