Conservation of Electric Energy - AP Physics 2

1. What is the relationship between electric potential and potential energy?

   $U = qV$. Potential energy equals charge times electric potential.

2. What is the potential energy of a charge in a field with zero potential difference?

   Zero. No potential difference means no stored energy.

3. What does the symbol $k_e$ represent in electric potential formulas?

   Coulomb's constant. Fundamental constant in Coulomb's law and electric formulas.

4. State the principle of conservation of electric energy.

   Total electric energy remains constant in an isolated system. Fundamental principle: energy cannot be created or destroyed.

5. Define the term 'electric potential'.

   Work done per unit charge to move a charge from infinity. Potential is work per unit charge from reference point.

6. What is the potential energy of a 2C charge at a potential of 5V?

   $U = 10 \text{ J}$. Using $U = qV = 2 \times 5 = 10$ J.

7. Calculate the electric potential energy for $q = 3C$ and $V = 4V$.

   $U = 12 \text{ J}$. Using $U = qV = 3 \times 4 = 12$ J.

8. State how electric potential energy changes when moving against the field.

   Increases. Moving against field requires work, increasing energy.

9. Calculate the electric potential energy for $q = 4C$ and $V = 6V$.

   $U = 24 \text{ J}$. Using $U = qV = 4 \times 6 = 24$ J.

10. What is the effect of increasing charge on electric potential energy?

    It increases linearly. Potential energy is directly proportional to charge.

11. Which factor does not affect electric potential energy in a uniform field?

    The direction of $d$. Direction doesn't affect energy magnitude in uniform fields.

12. Identify the relationship between work done and electric potential energy.

    $W = -\Delta U$. Work done equals negative change in potential energy.

13. Identify the unit of electric potential energy in the SI system.

    Joule (J). Standard SI unit for energy in all forms including electric.

14. Find the change in electric potential energy if $q = 2C$ and $\Delta V = 5V$.

    $\Delta U = 10 \text{ J}$. Using $\Delta U = q\Delta V = 2 \times 5 = 10$ J.

15. What happens to electric potential energy if charge is doubled?

    It doubles. Energy is directly proportional to charge magnitude.

16. Calculate the work done if a charge $q = 5C$ moves through $\Delta V = 3V$.

    $W = 15 \text{ J}$. Using $W = q\Delta V = 5 \times 3 = 15$ J.

17. What is the formula for electric potential energy?

    $U = qV$. Energy stored in charge $q$ at electric potential $V$.

18. Identify what must be true for electric energy conservation in a circuit.

    Closed circuit, no external work. Requirements for energy conservation in electrical systems.

19. What is the unit of electric potential in the SI system?

    Volt (V). Standard SI unit for electric potential difference.

20. Identify the effect on potential energy if distance increases in a point charge field.

    Decreases. Potential energy varies as $1/r$ for point charges.

21. What quantity does the symbol $U$ represent in electric energy equations?

    Electric potential energy. Standard symbol for electric potential energy in physics.

22. Identify the formula for converting potential difference to electric field strength.

    $E = -\frac{\Delta V}{d}$. Relationship between field strength and potential gradient.

23. What is the unit of Coulomb's constant $k_e$?

    $\text{N} \cdot \text{m}^2/\text{C}^2$. Units derived from Coulomb's law force equation.

24. What is the change in potential energy if a charge is moved to a lower potential?

    Decreases. Lower potential means reduced stored energy.

25. Calculate the potential energy change for $q = 1C$ and $\Delta V = -2V$.

    $\Delta U = -2 \text{ J}$. Using $\Delta U = q\Delta V = 1 \times (-2) = -2$ J.

26. State the formula for electric potential due to a point charge.

    $V = k_e \frac{q}{r}$. Potential created by point charge $q$ at distance $r$.

27. What is the effect on potential energy if a charge is halved?

    Halves. Energy is directly proportional to charge.

28. What does the conservation of electric energy imply for potential changes?

    Sum of changes is zero. Net energy change is zero in conservative systems.

29. What is the formula for the work done by an electric field?

    $W = qEd$. Work equals force times distance in uniform field.

30. State the expression for the electric potential difference in a uniform field.

    $\Delta V = Ed$. Potential difference in uniform field over distance $d$.

31. State what happens to potential energy when a charge moves with the field.

    Decreases. Field does positive work, reducing potential energy.

32. How does electric potential energy change with distance in a uniform field?

    Decreases with distance. Energy decreases as charge moves with field direction.

33. State the formula for electric potential energy in a uniform electric field.

    $U = qEd$. Energy stored in charge within uniform electric field.

34. How does electric potential vary with distance from a point charge?

    Inversely proportional. Potential follows inverse square law like electric field.

35. Identify the relationship between electric field strength and potential difference.

    $E = -\frac{\Delta V}{d}$. Electric field is negative gradient of potential.

36. Calculate the potential energy for $q = 3C$ and $V = -2V$.

    $U = -6 \text{ J}$. Using $U = qV = 3 \times (-2) = -6$ J.

37. Which physical quantity is conserved in an isolated electric system?

    Electric energy. Total electric energy remains constant in isolated systems.

38. What is the formula for the potential energy of a dipole in an electric field?

    $U = -pE \cos \theta$. Energy depends on dipole moment and field alignment.

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