AP Physics 2 Flashcards: Electric Potential Energy

What this deck covers

This deck focuses on Electric Potential Energy, giving you a quick way to review the definitions, rules, and examples that matter most for AP Physics 2.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: If $q = 5 \text{ C}$, $E = 10 \text{ N/C}$, $d = 2 \text{ m}$, find $U$.

Answer: $U = 100 \text{ J}$. Direct substitution: $U = 5 \times 10 \times 2 = 100$ J.

Flashcard 2: State the relationship between electric potential ($V$) and electric potential energy ($U$).

Answer: $U = qV$. Direct relationship between potential energy and electric potential.

Flashcard 3: State the potential energy of a dipole in a uniform electric field.

Answer: $U = -pE \text{ cos } \theta$. Energy depends on dipole alignment relative to field direction.

Flashcard 4: What is the relationship between equipotential surfaces and electric field lines?

Answer: They are perpendicular to each other. Electric field always points perpendicular to equipotential surfaces.

Flashcard 5: What happens to electric potential energy when opposite charges are brought closer?

Answer: Electric potential energy decreases. Attractive force releases energy as charges approach each other.

Flashcard 6: What is the potential energy difference if a charge $q$ moves through a potential difference $V$?

Answer: $\triangle U = q\triangle V$. Change in potential energy equals charge times potential difference.

Flashcard 7: What is electric potential energy?

Answer: Energy stored in a system due to electric forces. Energy from charge interactions and positions in electric fields.

Flashcard 8: State the relationship between electric potential ($V$) and electric potential energy ($U$).

Answer: $U = qV$. Direct relationship between potential energy and electric potential.

Flashcard 9: What is the unit of electric potential energy in the SI system?

Answer: Joule (J). Standard SI unit for all forms of energy.

Flashcard 10: If $U = 50 \text{ J}$ and $q = 2 \text{ C}$, what is $V$?

Answer: $V = 25 \text{ V}$. Solving $U = qV$ for potential: $V = \frac{50}{2} = 25$ V.

Flashcard 11: What is the electric potential energy of a charge at infinity?

Answer: Zero, as potential energy approaches zero at infinity. Infinity serves as the standard reference point for potential energy.

Flashcard 12: Define electric potential.

Answer: Electric potential is the potential energy per unit charge. Potential energy divided by charge gives potential at a point.

Flashcard 13: What does a negative electric potential energy indicate about the interaction between charges?

Answer: Attractive interaction between opposite charges. Opposite charges attract, releasing energy when brought together.

Flashcard 14: Calculate the potential energy: $p = 2 \text{ C} \text{ m}$, $E = 3 \text{ N/C}$, $\theta = 0^\text{o}$.

Answer: $U = -6 \text{ J}$. With $\theta = 0°$: $U = -2 \times 3 \times 1 = -6$ J.

Flashcard 15: What happens to electric potential energy when opposite charges are brought closer?

Answer: Electric potential energy decreases. Attractive force releases energy as charges approach each other.

Flashcard 16: What is zero electric potential energy?

Answer: Reference point where potential energy is defined as zero. Arbitrary reference point chosen for convenience in calculations.

Flashcard 17: What happens to electric potential energy when like charges are brought closer?

Answer: Electric potential energy increases. Repulsive force requires work to decrease separation distance.

Flashcard 18: What is the potential energy formula for a capacitor with capacitance $C$ and voltage $V$?

Answer: $U = \frac{1}{2} CV^2$. Energy stored in electric field between capacitor plates.

Flashcard 19: For a charge $q$ in a field $E$, what is the work done moving it a distance $d$?

Answer: $W = -qEd$. Negative sign indicates work done against the electric field.

Flashcard 20: What is the potential energy of a charge $q$ in the presence of a uniform electric field $E$?

Answer: $U = qEd$. Energy stored when charge is displaced distance $d$ in uniform field.

Flashcard 21: Define equipotential surface.

Answer: Surface where electric potential is constant. Surface of points having identical electric potential values.

Flashcard 22: What is the relationship between equipotential surfaces and electric field lines?

Answer: They are perpendicular to each other. Electric field always points perpendicular to equipotential surfaces.

Flashcard 23: Calculate potential energy change: $q = 2 \text{ C}$, $\triangle V = 5 \text{ V}$.

Answer: $\triangle U = 10 \text{ J}$. Direct calculation: $\triangle U = 2 \times 5 = 10$ J.

Flashcard 24: What is the formula for the potential energy stored in a capacitor?

Answer: $U = \frac{1}{2} CV^2$. Standard formula for energy stored in capacitor electric field.

Flashcard 25: What is the potential energy change if a charge moves in a radial electric field?

Answer: Calculated using $U = k_e \frac{q_1 q_2}{r}$. Use the two-point charge formula for radial field configurations.

Flashcard 26: What is zero electric potential energy?

Answer: Reference point where potential energy is defined as zero. Arbitrary reference point chosen for convenience in calculations.

Flashcard 27: For a charge $q$ in a field $E$, what is the work done moving it a distance $d$?

Answer: $W = -qEd$. Negative sign indicates work done against the electric field.

Flashcard 28: State the potential energy formula for a point charge $q$ in a potential $V$.

Answer: $U = qV$. Fundamental relationship between charge, potential, and potential energy.

Flashcard 29: What does a negative electric potential energy indicate about the interaction between charges?

Answer: Attractive interaction between opposite charges. Opposite charges attract, releasing energy when brought together.

Flashcard 30: What is the potential energy formula for a capacitor with capacitance $C$ and voltage $V$?

Answer: $U = \frac{1}{2} CV^2$. Energy stored in electric field between capacitor plates.

Flashcard 31: What is the expression for electric potential energy in a uniform field?

Answer: $U = qEd$. Formula for potential energy in constant electric field.

Flashcard 32: Calculate potential energy: $q = 3 \text{ C}$, $V = 4 \text{ V}$.

Answer: $U = 12 \text{ J}$. Direct substitution: $U = 3 \times 4 = 12$ J.

Flashcard 33: What happens to electric potential energy when like charges are brought closer?

Answer: Electric potential energy increases. Repulsive force requires work to decrease separation distance.

Flashcard 34: What is the potential energy change if a charge moves in a radial electric field?

Answer: Calculated using $U = k_e \frac{q_1 q_2}{r}$. Use the two-point charge formula for radial field configurations.

Flashcard 35: What is the electric potential energy of a charge at infinity?

Answer: Zero, as potential energy approaches zero at infinity. Infinity serves as the standard reference point for potential energy.

Flashcard 36: State the potential energy of a dipole in a uniform electric field.

Answer: $U = -pE \text{ cos } \theta$. Energy depends on dipole alignment relative to field direction.

Flashcard 37: State the formula for electric potential energy between two point charges.

Answer: $U = k_e \frac{q_1 q_2}{r}$. Direct formula from Coulomb's law for two point charges.

Flashcard 38: Calculate the potential energy of a capacitor: $C = 4 \text{ F}$, $V = 5 \text{ V}$.

Answer: $U = 50 \text{ J}$. Using $U = \frac{1}{2} \times 4 \times 5^2 = 50$ J.

Flashcard 39: If $q = 5 \text{ C}$, $E = 10 \text{ N/C}$, $d = 2 \text{ m}$, find $U$.

Answer: $U = 100 \text{ J}$. Direct substitution: $U = 5 \times 10 \times 2 = 100$ J.

Flashcard 40: In a capacitor, how does increasing the separation affect potential energy?

Answer: Increases potential energy. Larger separation increases energy stored in electric field.

Flashcard 41: What is electric potential energy?

Answer: Energy stored in a system due to electric forces. Energy from charge interactions and positions in electric fields.

Flashcard 42: Identify the constant $k_e$ in the formula $U = k_e \frac{q_1 q_2}{r}$.

Answer: Coulomb's constant, $8.99 \times 10^9 \text{ N m}^2/\text{C}^2$. Fundamental constant relating electric force and charge separation.

Flashcard 43: What is the electric potential energy change for a charge moving through a potential difference?

Answer: $\triangle U = q \triangle V$. Change in potential energy from moving through potential difference.

Flashcard 44: What is the electric potential energy of a charge $q$ at a potential $V$?

Answer: $U = qV$. Direct application of the potential energy-potential relationship.

Flashcard 45: What is the potential energy difference if a charge $q$ moves through a potential difference $V$?

Answer: $\triangle U = q\triangle V$. Change in potential energy equals charge times potential difference.

Flashcard 46: What is the electric potential energy of a charge $q$ at a potential $V$?

Answer: $U = qV$. Direct application of the potential energy-potential relationship.

Flashcard 47: In a capacitor, how does increasing the separation affect potential energy?

Answer: Increases potential energy. Larger separation increases energy stored in electric field.

Flashcard 48: What is the electric potential energy of a system of two point charges $q_1$, $q_2$ separated by $r$?

Answer: $U = k_e \frac{q_1 q_2}{r}$. Standard two-charge potential energy formula from Coulomb's law.

Flashcard 49: What is the electric potential energy change for a charge moving through a potential difference?

Answer: $\triangle U = q \triangle V$. Change in potential energy from moving through potential difference.

Flashcard 50: Calculate the work done: $q = 4 \text{ C}$, $E = 5 \text{ N/C}$, $d = 3 \text{ m}$.

Answer: $W = -60 \text{ J}$. Direct calculation: $W = -4 \times 5 \times 3 = -60$ J.

Flashcard 51: Find the potential energy of a system with $q_1 = 1 \text{ C}$, $q_2 = 2 \text{ C}$, and $r = 0.5 \text{ m}$.

Answer: $U = 35.96 \times 10^9 \text{ J}$. Using $U = 8.99 \times 10^9 \times \frac{1 \times 2}{0.5}$.

Flashcard 52: What is the expression for electric potential energy in a uniform field?

Answer: $U = qEd$. Formula for potential energy in constant electric field.

Flashcard 53: What does a positive electric potential energy indicate about the interaction between charges?

Answer: Repulsive interaction between like charges. Same charges repel, requiring energy to bring them together.

Flashcard 54: What is the formula for the potential energy stored in a capacitor?

Answer: $U = \frac{1}{2} CV^2$. Standard formula for energy stored in capacitor electric field.

Flashcard 55: If $U = 50 \text{ J}$ and $q = 2 \text{ C}$, what is $V$?

Answer: $V = 25 \text{ V}$. Solving $U = qV$ for potential: $V = \frac{50}{2} = 25$ V.

Flashcard 56: What is the electric potential energy of a system of two point charges $q_1$, $q_2$ separated by $r$?

Answer: $U = k_e \frac{q_1 q_2}{r}$. Standard two-charge potential energy formula from Coulomb's law.

Flashcard 57: Calculate the electric potential energy: $q_1 = 2 \text{ C}$, $q_2 = 3 \text{ C}$, $r = 1 \text{ m}$.

Answer: $U = 5.394 \times 10^{10} \text{ J}$. Using $U = k_e \frac{q_1 q_2}{r} = 8.99 \times 10^9 \times \frac{2 \times 3}{1}$.

Flashcard 58: Calculate potential energy change: $q = 2 \text{ C}$, $\triangle V = 5 \text{ V}$.

Answer: $\triangle U = 10 \text{ J}$. Direct calculation: $\triangle U = 2 \times 5 = 10$ J.

Flashcard 59: Calculate the work done: $q = 4 \text{ C}$, $E = 5 \text{ N/C}$, $d = 3 \text{ m}$.

Answer: $W = -60 \text{ J}$. Direct calculation: $W = -4 \times 5 \times 3 = -60$ J.

Flashcard 60: Calculate the potential energy: $p = 2 \text{ C} \text{ m}$, $E = 3 \text{ N/C}$, $\theta = 0^\text{o}$.

Answer: $U = -6 \text{ J}$. With $\theta = 0°$: $U = -2 \times 3 \times 1 = -6$ J.

Flashcard 61: Define equipotential surface.

Answer: Surface where electric potential is constant. Surface of points having identical electric potential values.

Flashcard 62: What is the unit of electric potential energy in the SI system?

Answer: Joule (J). Standard SI unit for all forms of energy.

Flashcard 63: What does a positive electric potential energy indicate about the interaction between charges?

Answer: Repulsive interaction between like charges. Same charges repel, requiring energy to bring them together.

Flashcard 64: Calculate the electric potential energy: $q_1 = 2 \text{ C}$, $q_2 = 3 \text{ C}$, $r = 1 \text{ m}$.

Answer: $U = 5.394 \times 10^{10} \text{ J}$. Using $U = k_e \frac{q_1 q_2}{r} = 8.99 \times 10^9 \times \frac{2 \times 3}{1}$.

Flashcard 65: Calculate potential energy: $q = 3 \text{ C}$, $V = 4 \text{ V}$.

Answer: $U = 12 \text{ J}$. Direct substitution: $U = 3 \times 4 = 12$ J.

Flashcard 66: What is the potential energy of a charge $q$ in the presence of a uniform electric field $E$?

Answer: $U = qEd$. Energy stored when charge is displaced distance $d$ in uniform field.

Flashcard 67: Calculate the potential energy of a capacitor: $C = 4 \text{ F}$, $V = 5 \text{ V}$.

Answer: $U = 50 \text{ J}$. Using $U = \frac{1}{2} \times 4 \times 5^2 = 50$ J.

Flashcard 68: State the formula for electric potential energy between two point charges.

Answer: $U = k_e \frac{q_1 q_2}{r}$. Direct formula from Coulomb's law for two point charges.

Flashcard 69: Identify the constant $k_e$ in the formula $U = k_e \frac{q_1 q_2}{r}$.

Answer: Coulomb's constant, $8.99 \times 10^9 \text{ N m}^2/\text{C}^2$. Fundamental constant relating electric force and charge separation.