Conservation of Electric Energy - AP Physics C: Electricity and Magnetism
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What is the unit of electric potential energy?
What is the unit of electric potential energy?
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Joule (J). Same unit as mechanical energy.
Joule (J). Same unit as mechanical energy.
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What happens to electric energy in a closed system?
What happens to electric energy in a closed system?
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It remains constant. Conservation law for isolated electric systems.
It remains constant. Conservation law for isolated electric systems.
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State the energy conservation law in electrical circuits.
State the energy conservation law in electrical circuits.
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Energy supplied = Energy consumed + Energy stored. Fundamental energy balance in electrical systems.
Energy supplied = Energy consumed + Energy stored. Fundamental energy balance in electrical systems.
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What is the formula for power in terms of current and voltage?
What is the formula for power in terms of current and voltage?
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$P = IV$. Power is rate of energy transfer.
$P = IV$. Power is rate of energy transfer.
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What is the unit of electric field energy density?
What is the unit of electric field energy density?
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Joules per cubic meter (J/m³). Energy density has units of energy per volume.
Joules per cubic meter (J/m³). Energy density has units of energy per volume.
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What is the energy formula in terms of voltage and capacitance?
What is the energy formula in terms of voltage and capacitance?
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$U = \frac{1}{2}CV^2$. Standard capacitor energy formula.
$U = \frac{1}{2}CV^2$. Standard capacitor energy formula.
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State the energy conservation equation for electric circuits.
State the energy conservation equation for electric circuits.
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$\text{Energy input} = \text{Energy output}$. Fundamental principle of energy conservation.
$\text{Energy input} = \text{Energy output}$. Fundamental principle of energy conservation.
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What is the unit of electric potential difference?
What is the unit of electric potential difference?
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Volt (V). Standard unit for electric potential.
Volt (V). Standard unit for electric potential.
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State the formula for power in terms of resistance and current.
State the formula for power in terms of resistance and current.
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$P = I^2R$. Power dissipated through resistance.
$P = I^2R$. Power dissipated through resistance.
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Calculate the energy stored for $q = 4 \text{ C}$ and $C = 8 \text{ F}$.
Calculate the energy stored for $q = 4 \text{ C}$ and $C = 8 \text{ F}$.
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$1 \text{ J}$. Using $U = \frac{q^2}{2C} = \frac{16}{16}$.
$1 \text{ J}$. Using $U = \frac{q^2}{2C} = \frac{16}{16}$.
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What is the formula for energy stored in terms of charge and capacitance?
What is the formula for energy stored in terms of charge and capacitance?
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$U = \frac{q^2}{2C}$. Alternative form using charge and capacitance.
$U = \frac{q^2}{2C}$. Alternative form using charge and capacitance.
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Identify the electric energy formula for charge $q$ and potential $V$.
Identify the electric energy formula for charge $q$ and potential $V$.
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$U = qV$. Basic formula for electric potential energy.
$U = qV$. Basic formula for electric potential energy.
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What is the formula for electric energy loss in a resistor?
What is the formula for electric energy loss in a resistor?
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$P = I^2R$. Power dissipated as heat in resistor.
$P = I^2R$. Power dissipated as heat in resistor.
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State the formula for energy stored in an electric field.
State the formula for energy stored in an electric field.
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$U = \frac{1}{2} \text{ε}_0 E^2 A d$. Total energy stored in uniform electric field.
$U = \frac{1}{2} \text{ε}_0 E^2 A d$. Total energy stored in uniform electric field.
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What happens to electric energy in a closed system?
What happens to electric energy in a closed system?
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It remains constant. Conservation law for isolated electric systems.
It remains constant. Conservation law for isolated electric systems.
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Calculate energy stored in an inductor with $L=2 \text{ H}$ and $I=3 \text{ A}$.
Calculate energy stored in an inductor with $L=2 \text{ H}$ and $I=3 \text{ A}$.
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$9 \text{ J}$. Using $U = \frac{1}{2}LI^2 = \frac{1}{2}(2)(3)^2$.
$9 \text{ J}$. Using $U = \frac{1}{2}LI^2 = \frac{1}{2}(2)(3)^2$.
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What is the unit of electric field energy density?
What is the unit of electric field energy density?
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Joules per cubic meter (J/m³). Energy density has units of energy per volume.
Joules per cubic meter (J/m³). Energy density has units of energy per volume.
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State the energy conservation law in electrical circuits.
State the energy conservation law in electrical circuits.
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Energy supplied = Energy consumed + Energy stored. Fundamental energy balance in electrical systems.
Energy supplied = Energy consumed + Energy stored. Fundamental energy balance in electrical systems.
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Find the potential energy change for $q = 2 \text{ C}$ moving from $3 \text{ V}$ to $5 \text{ V}$.
Find the potential energy change for $q = 2 \text{ C}$ moving from $3 \text{ V}$ to $5 \text{ V}$.
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$4 \text{ J}$. Change equals charge times voltage difference: $2(5-3)$.
$4 \text{ J}$. Change equals charge times voltage difference: $2(5-3)$.
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State the energy conservation equation for an LC circuit.
State the energy conservation equation for an LC circuit.
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$\frac{1}{2}CV^2 + \frac{1}{2}LI^2 = \text{constant}$. Energy oscillates between electric and magnetic forms.
$\frac{1}{2}CV^2 + \frac{1}{2}LI^2 = \text{constant}$. Energy oscillates between electric and magnetic forms.
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State the formula for the energy of a moving charge in an electric field.
State the formula for the energy of a moving charge in an electric field.
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$U = qEd$. Energy of charge moving through electric field.
$U = qEd$. Energy of charge moving through electric field.
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What is the principle of conservation of electric energy?
What is the principle of conservation of electric energy?
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Total electric energy is constant in a closed system. Energy cannot be created or destroyed in electric systems.
Total electric energy is constant in a closed system. Energy cannot be created or destroyed in electric systems.
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State the formula for electric potential energy.
State the formula for electric potential energy.
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$U = qV$. Energy equals charge times electric potential.
$U = qV$. Energy equals charge times electric potential.
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Identify the relationship between electric field and energy density.
Identify the relationship between electric field and energy density.
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$u = \frac{1}{2} \text{ε}_0 E^2$. Energy density proportional to field squared.
$u = \frac{1}{2} \text{ε}_0 E^2$. Energy density proportional to field squared.
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Calculate power consumed by a $5 \text{ A}$ current through $10 \text{ V}$.
Calculate power consumed by a $5 \text{ A}$ current through $10 \text{ V}$.
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$50 \text{ W}$. Power equals current times voltage: $5 \times 10$.
$50 \text{ W}$. Power equals current times voltage: $5 \times 10$.
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What quantity is conserved in an electrostatic process?
What quantity is conserved in an electrostatic process?
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Electric energy. Conserved quantity in electrostatic interactions.
Electric energy. Conserved quantity in electrostatic interactions.
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What is the unit of electric potential energy?
What is the unit of electric potential energy?
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Joule (J). Same unit as mechanical energy.
Joule (J). Same unit as mechanical energy.
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Calculate the energy stored in a $10 \text{ F}$ capacitor with $5 \text{ V}$ potential.
Calculate the energy stored in a $10 \text{ F}$ capacitor with $5 \text{ V}$ potential.
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$125 \text{ J}$. Using $U = \frac{1}{2}CV^2 = \frac{1}{2}(10)(5)^2$.
$125 \text{ J}$. Using $U = \frac{1}{2}CV^2 = \frac{1}{2}(10)(5)^2$.
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Calculate the work done moving $3 \text{ C}$ through $10 \text{ V}$.
Calculate the work done moving $3 \text{ C}$ through $10 \text{ V}$.
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$30 \text{ J}$. Work equals charge times potential difference: $3 \times 10$.
$30 \text{ J}$. Work equals charge times potential difference: $3 \times 10$.
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What is the formula for power in terms of current and voltage?
What is the formula for power in terms of current and voltage?
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$P = IV$. Power is rate of energy transfer.
$P = IV$. Power is rate of energy transfer.
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