Electric Fields - AP Physics 2

1. State the formula for the electric field between two parallel plates.

   $E = \frac{V}{d}$. Uniform field between plates equals voltage divided by separation.

2. What is the direction of the electric field due to a negative point charge?

   Radially inward towards the charge. Electric field points toward negative charges in all directions.

3. What is the charge of an electron?

   $-1.6 \times 10^{-19}$ C. Elementary negative charge magnitude in coulombs.

4. Explain the change in electric field strength if the charge is tripled.

   Field strength is tripled. Field strength is directly proportional to the source charge magnitude.

5. What is the direction of electric field lines around a dipole?

   From positive to negative charge. Field lines exit positive charges and enter negative charges.

6. What is the electric field due to a charge distribution at infinity?

   Zero. Field approaches zero as distance approaches infinity for finite charges.

7. What is the electric field inside a conductor in electrostatic equilibrium?

   Zero. Free charges redistribute to cancel internal fields in equilibrium.

8. Which principle explains the behavior of electric fields in superposition?

   Principle of superposition. Vector addition of individual field contributions from multiple sources.

9. What is the effect of a conductor on the external electric field?

   Distorts and reduces the field inside. Conductor redistributes charges and creates field-free interior region.

10. What is the electric field at the surface of a conductor?

    Perpendicular to the surface. Electric field must be normal to conductor surface in equilibrium.

11. What is the effect of a grounded conductor on nearby electric field lines?

    Field lines terminate on the conductor. Grounded conductors provide discharge path, terminating field lines.

12. State Gauss's law for electric fields.

    $\oint E \cdot dA = \frac{Q_{enclosed}}{\varepsilon_0}$. Fundamental relationship between electric flux and enclosed charge.

13. State the unit of electric field strength in the SI system.

    Newton per coulomb (N/C). Standard SI unit combining force (N) per unit charge (C).

14. Determine the electric field inside a hollow charged spherical conductor.

    Zero. No charges inside hollow conductor means zero internal field.

15. What is the effect of doubling the distance between a charge and a point in the field?

    Electric field decreases by a factor of 4. Inverse square law: field strength decreases by factor of four.

16. What is the relation between electric field and electric potential?

    $E = -\frac{dV}{dx}$. Field is the negative gradient of potential in one dimension.

17. What happens to the electric field if the distance from a point charge is doubled?

    Field strength decreases by a factor of 4. Inverse square relationship: doubling distance quarters the field strength.

18. State Coulomb's law in terms of force between two point charges.

    $F = \frac{k |q_1 q_2|}{r^2}$. Force between charges depends on product of charges and inverse square of distance.

19. What is the effect of introducing a dielectric in a parallel plate capacitor?

    Reduces the electric field. Dielectric materials decrease field strength by polarization effects.

20. Identify the electric field at the center of a uniformly charged ring.

    Zero. Symmetry causes all field contributions to cancel at the center.

21. Determine the net electric field at a point equidistant from two equal charges.

    Zero, if charges are opposite. Equal magnitudes but opposite directions cancel when charges are opposite.

22. Which quantity measures the work done per unit charge by an electric field?

    Electric potential. Potential represents energy per unit charge in electric field.

23. What is the electric field at a point outside a charged sphere?

    Same as a point charge: $E = \frac{kQ}{r^2}$. Spherical symmetry makes external field identical to point charge.

24. Find the electric field at a point midway between two equal positive charges.

    Zero. Symmetry causes equal and opposite field contributions to cancel.

25. Define an electric dipole.

    Two equal and opposite charges separated by a distance. Basic configuration creating electric dipole moment and field pattern.

26. Identify the direction of the electric field around a positive point charge.

    Radially outward from the charge. Electric field points away from positive charges in all directions.

27. What is the electric field at a point with zero electric potential?

    Not necessarily zero. Field and potential are related but independent quantities.

28. How does the electric field between parallel plates depend on the area of the plates?

    Field is independent of the plate area. Field depends only on charge density and plate separation, not area.

29. What is the formula for the electric field due to a point charge?

    $E = \frac{kQ}{r^2}$. Coulomb's law applied to field strength, where $k$ is the electric constant.

30. What is the value of the electric constant $k$ in vacuum?

    $k = 8.99 \times 10^9 \text{ N m}^2/\text{C}^2$. Standard value for the proportionality constant in vacuum.

31. What is the relationship between electric field and force on a charge?

    $F = qE$. Force equals charge multiplied by electric field strength.

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