6. Circuits Flashcards
Capacitance (C) formula. Definition of capacitance and factors affecting it
C = Q/deltaVoltage in Farads; Q = charge in C
Storage of charge per unit voltage. Made up of 2 parallel conducting plates separated by insulating material or vacuum. IF YOU WANT TO CHARGE SOMETHING FAST, DEC THE CAPACITANCE SINCE IT’S STORING CHARGE
Capacitance = directly proportional to area and inversely proportional to distance: C = epsilon_0*(A/d) where epsilon_0=permittivity of free space, A=area of overlap b/w 2 plates, and d=separation of 2 plates
Voltage (V) formula aka Ohm’s Law
V = IR
Current (I) formula. What’s the direction of current?
charge over time = Q/t, units: Amperes
Direction a pos charge would flow: high to low potential (ie. Based on flow of e- moving from low potential to high potential, so technically direction of current flows opposite to flow of e-); current by definition = moving charge in space
How to add up resistors in a series circuit? In a parallel circuit?
Rtotal = R1 + R2 + R3... etc for series 1/Rtotal = 1/R1 + 1/R2 + 1/R3... etc for parallel
In a series circuit, what happens to values of V, I and R?
V: voltage = diff for each resistor
I: current = constant throughout entire circuit
R: resistance can be diff
In a parallel circuit, what happens to values of V, I and R?
V: voltage = same for each resistor
I: current = diff when splitting into parallel circuits but are additive
R: resistance can be diff
How to add up capacitors in a series circuit? In a parallel circuit?
1/Ctotal = 1/C1 + 1/C2 + 1/C3... etc for series Ctotal = C1 + C2 + C3... etc for parallel
In a series circuit, what happens to values of V, Q and C?
V: voltage = diff for each capacitor but is additive
Q: charge = same for all capacitors throughout circuit –> find Ceq to find charge
C: capacitance can be diff
In a parallel circuit, what happens to values of V, Q and C?
V: voltage = same for all capacitors throughout circuit
Q: charge = diff for each capacitor but is additive to Ceq charge
C: capacitance can be diff
Definition of resistance, formula, and factors affecting it
Opposition to flow of charge. R = (rho*L)/A
Length = directly proportional to resistance: double the length of resistor —> double the resistance
Cross-sectional area = inversely proportional to resistance: double the cross-sectional area —> half the resistance (cuz inc area means more pathways thru resistor => conduction pathways); thicker wire => bigger cross sectional area; A IS NOT SURFACE AREA
Higher temp —> greater resistance
Adding a resistor to a capacitor would dec V in series and keep V constant in parallel
Power is dissipated by resistors. What’s the formula relating to power and resistance?
P = I^2*R and you can rearrange it to P = IV and P = V^2/R; it’s the rate of electrical energy transferred
Potential energy stored by capacitors formula
U = 1/2CV^2 and you can rearrange it
Kirchhoff’s junction rule vs loop rule
Current vs voltage in is the same going out (additive)
Direct vs alternative current
Charge flows in 1 direction only vs charge flow changes direction periodically
Dielectric material and dielectric constant
Another way to say insulator —> stores more charge for capacitor by a factor of the constant. Higher dielectric constant —> higher insulation —> inc capacitance —> stores more charge. The constant will NEVER be less than 1 b/c dielectric materials will NEVER dec capacitance. It’s polarizeable b/c its molec have dipoles that can be oriented in particular directions
