Capacitors - AP Physics C: Electricity and Magnetism
Card 1 of 30
State the formula for capacitors in parallel.
State the formula for capacitors in parallel.
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$C_{\text{eq}} = C_1 + C_2 + \dots$. Parallel capacitors add directly like series resistors.
$C_{\text{eq}} = C_1 + C_2 + \dots$. Parallel capacitors add directly like series resistors.
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State the formula for the capacitance of a parallel plate capacitor.
State the formula for the capacitance of a parallel plate capacitor.
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$C = \frac{\varepsilon A}{d}$. Capacitance depends on area $A$, distance $d$, and permittivity $\varepsilon$.
$C = \frac{\varepsilon A}{d}$. Capacitance depends on area $A$, distance $d$, and permittivity $\varepsilon$.
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What does the time constant $\tau$ signify in an RC circuit?
What does the time constant $\tau$ signify in an RC circuit?
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Time to reach $63%$ of final value. Characteristic time for exponential charging or discharging process.
Time to reach $63%$ of final value. Characteristic time for exponential charging or discharging process.
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What effect does a dielectric have on capacitance?
What effect does a dielectric have on capacitance?
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Increases capacitance. Dielectric constant $k > 1$ multiplies the capacitance.
Increases capacitance. Dielectric constant $k > 1$ multiplies the capacitance.
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What is the unit of capacitance?
What is the unit of capacitance?
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Farad (F). Named after Michael Faraday, represents charge per unit voltage.
Farad (F). Named after Michael Faraday, represents charge per unit voltage.
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Define the time constant for an RC circuit.
Define the time constant for an RC circuit.
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$\tau = RC$. Product of resistance and capacitance determines charging rate.
$\tau = RC$. Product of resistance and capacitance determines charging rate.
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Identify the energy stored in a capacitor formula.
Identify the energy stored in a capacitor formula.
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$U = \frac{1}{2}CV^2$. Energy is proportional to capacitance and voltage squared.
$U = \frac{1}{2}CV^2$. Energy is proportional to capacitance and voltage squared.
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How does adding a dielectric change the capacitance?
How does adding a dielectric change the capacitance?
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Increases capacitance. Dielectric material increases capacitance by factor $k$.
Increases capacitance. Dielectric material increases capacitance by factor $k$.
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Identify the formula for charge on a capacitor in a DC circuit.
Identify the formula for charge on a capacitor in a DC circuit.
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$Q = CV$. Fundamental relationship between charge, capacitance, and voltage.
$Q = CV$. Fundamental relationship between charge, capacitance, and voltage.
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What is the equation for voltage across a discharging capacitor?
What is the equation for voltage across a discharging capacitor?
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$V(t) = V_0 e^{-t/RC}$. Exponential decay from initial voltage with time constant $RC$.
$V(t) = V_0 e^{-t/RC}$. Exponential decay from initial voltage with time constant $RC$.
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State the formula for equivalent capacitance in parallel.
State the formula for equivalent capacitance in parallel.
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$C_{\text{eq}} = C_1 + C_2 + \dots$. Parallel capacitors combine by direct addition of values.
$C_{\text{eq}} = C_1 + C_2 + \dots$. Parallel capacitors combine by direct addition of values.
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State the formula for capacitors in parallel.
State the formula for capacitors in parallel.
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$C_{\text{eq}} = C_1 + C_2 + \dots$. Parallel capacitors add directly like series resistors.
$C_{\text{eq}} = C_1 + C_2 + \dots$. Parallel capacitors add directly like series resistors.
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What happens to capacitance if the plate area increases?
What happens to capacitance if the plate area increases?
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Capacitance increases. From $C = \frac{\varepsilon A}{d}$, capacitance is directly proportional to area.
Capacitance increases. From $C = \frac{\varepsilon A}{d}$, capacitance is directly proportional to area.
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What happens to stored energy if capacitance doubles?
What happens to stored energy if capacitance doubles?
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Stored energy doubles. From $U = \frac{1}{2}CV^2$, energy is directly proportional to capacitance.
Stored energy doubles. From $U = \frac{1}{2}CV^2$, energy is directly proportional to capacitance.
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State the relationship between charge, voltage, and capacitance.
State the relationship between charge, voltage, and capacitance.
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$Q = CV$. Fundamental relationship defining capacitance as charge per voltage.
$Q = CV$. Fundamental relationship defining capacitance as charge per voltage.
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What is the dielectric breakdown?
What is the dielectric breakdown?
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Failure of dielectric under high voltage. Electric field exceeds dielectric strength, causing material failure.
Failure of dielectric under high voltage. Electric field exceeds dielectric strength, causing material failure.
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State the relationship between energy, capacitance, and voltage.
State the relationship between energy, capacitance, and voltage.
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$U = \frac{1}{2}CV^2$. Energy stored is half the product of capacitance and voltage squared.
$U = \frac{1}{2}CV^2$. Energy stored is half the product of capacitance and voltage squared.
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What is the formula for work done to charge a capacitor?
What is the formula for work done to charge a capacitor?
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$W = \frac{1}{2}CV^2$. Work equals energy stored in the electric field.
$W = \frac{1}{2}CV^2$. Work equals energy stored in the electric field.
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What is the energy density in a capacitor?
What is the energy density in a capacitor?
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$u = \frac{1}{2}\varepsilon E^2$. Energy density depends on permittivity and electric field squared.
$u = \frac{1}{2}\varepsilon E^2$. Energy density depends on permittivity and electric field squared.
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Identify the formula for energy stored in terms of charge.
Identify the formula for energy stored in terms of charge.
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$U = \frac{1}{2} \frac{Q^2}{C}$. Alternative energy formula using charge instead of voltage.
$U = \frac{1}{2} \frac{Q^2}{C}$. Alternative energy formula using charge instead of voltage.
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What is the effect of connecting capacitors in parallel?
What is the effect of connecting capacitors in parallel?
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Increases equivalent capacitance. Parallel connection sums individual capacitances.
Increases equivalent capacitance. Parallel connection sums individual capacitances.
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Identify the formula for the electric field in a capacitor.
Identify the formula for the electric field in a capacitor.
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$E = \frac{V}{d}$. Electric field equals voltage divided by plate separation.
$E = \frac{V}{d}$. Electric field equals voltage divided by plate separation.
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What factor does the dielectric constant affect?
What factor does the dielectric constant affect?
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Capacitance. Dielectric constant directly multiplies the capacitance value.
Capacitance. Dielectric constant directly multiplies the capacitance value.
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What is the effect of connecting capacitors in series?
What is the effect of connecting capacitors in series?
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Decreases equivalent capacitance. Series connection reduces total capacitance below smallest value.
Decreases equivalent capacitance. Series connection reduces total capacitance below smallest value.
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State the formula for the potential difference across a capacitor.
State the formula for the potential difference across a capacitor.
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$V = \frac{Q}{C}$. Voltage equals charge divided by capacitance.
$V = \frac{Q}{C}$. Voltage equals charge divided by capacitance.
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What is the relationship between charge and voltage in a capacitor?
What is the relationship between charge and voltage in a capacitor?
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$Q = CV$. Charge is proportional to both capacitance and voltage.
$Q = CV$. Charge is proportional to both capacitance and voltage.
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What is the effect of reducing the distance between capacitor plates?
What is the effect of reducing the distance between capacitor plates?
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Increases capacitance. From $C = \frac{\varepsilon A}{d}$, smaller $d$ increases capacitance.
Increases capacitance. From $C = \frac{\varepsilon A}{d}$, smaller $d$ increases capacitance.
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How does a dielectric affect the electric field in a capacitor?
How does a dielectric affect the electric field in a capacitor?
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Decreases the electric field. Dielectric reduces field by factor of dielectric constant $k$.
Decreases the electric field. Dielectric reduces field by factor of dielectric constant $k$.
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Identify the expression for the electric displacement field $D$.
Identify the expression for the electric displacement field $D$.
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$D = \varepsilon E$. Displacement field relates permittivity to electric field strength.
$D = \varepsilon E$. Displacement field relates permittivity to electric field strength.
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What does the symbol $\varepsilon_0$ represent?
What does the symbol $\varepsilon_0$ represent?
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Permittivity of free space. Fundamental constant relating electric field to electric displacement.
Permittivity of free space. Fundamental constant relating electric field to electric displacement.
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