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25 Cards in this Set
- Front
- Back
Insulator (Dielectric)
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Material put in a capacitor that increases storage
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Objects in Series
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There is no junction between them
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Objects in Parallel
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Their ends are directly connected
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κ (kappa)
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dielectric constant
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Capacitors in Series
Have same ____ MOE q123 = ___ Equation |
1) All have same charge
2) MOE: q123 = q1 = q2 = q3 3) Equation: 1 / Ceq |
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Kirchoff's Loop Rule
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The sum of potential changes around a closed loop = 0.
*Conservation of ENERGY Σ ΔV = 0 |
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Capacitors in Parallel
Have same ____ MOE q123 = ___ Equation |
1) All have same potential difference.
2) q123 = q1 + q2 + q3 3) Equation: C eq = C1 + C2 |
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Volt (unit)
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Joule / Coulomb
N*m / C Watt / Amp |
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Capacitance
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C = q / ΔV
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U (energy, charge stored)
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U = (1/2) * q * ΔV
= (1/2) * c * ΔV^2 = (1/2) * q^2 / C in Joules |
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Current (I)
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I == Δq / Δt
= coulomb / sec Units in Amperes Current in direction opposite electron flow |
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Drift velocity
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Very slow - 5e-4 m/s
"Monkeys drift down the mountain" |
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Current (full formula)
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I = Δq / Δt
= n*e*(v_d)*A n is number of charge carriers/unit vol v_d is drift velocity |
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Ohm's Law
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ΔV = I*R ("suggestion" that R is constant)
Resistance in Ohms Current Coulomb / sec |
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Resistance
(Ohm's law and full def) |
R = ΔV / I
= ρ * (l/A) where ρ is resistivity of material |
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Power
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Rate work is done
P = W / Δt = (I^2)*R = I*ΔV |
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Energy in circuit
Battery Capacitor Resistor |
Battery *provides* energy
Capacitor *stores* energy Resistor *uses* enerrgy |
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Resistors in Series
Have same ____ MOE q123 = ___ Equation |
1) All have same current
2) MOE: I123 = I1 = I2 = I3 3) Equation: R123 = R1 + R2 + R3 |
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Kirchoff's Point (Junction) Rule
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Current in = Current out
I1 = I2 + I3 (at junction) Conservation of charge |
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Resistors in Parallel
Have same ____ MOE q123 = ___ Equation |
1) All have same voltage
2) MOE: I123 = I1 + I2 + I3 3) Equation: 1/R123 = 1/R1 + 1/R2 |
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Capacitance of no capacitor
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Equal to 1/infinite = 0
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Capacitors
3 things to find |
1) q Charge
2) ΔV Voltage 3) C Energy stored |
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Resistors
3 things to find |
1) I Current
2) ΔV Voltage 3) P Energy used |
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Charging a Capacitor
When charging? Current does what? |
Charges when switch is closed
Current stops when fully charged |
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q(t)
Charging Capacitor |
q(t) = εC [ 1 - e^(-t/τ) ]
where τ = R*C (seconds) the time constant |