Conductors, Capacitors, and Dielectrics Practice Test 2

1.

Which of the following is a property of an ideal conductor in electrostatic equilibrium?

a) The electric field inside is uniform b) The electric field inside is zero c) The potential varies throughout the conductor d) The charge resides in the center

2.

Which of the following materials is a dielectric?

a) Silver b) Copper c) Glass d) Iron

3.

Three 6 μF capacitors are connected in parallel. What is the equivalent capacitance?

a) 2 μF b) 6 μF c) 12 μF d) 18 μF

4.

What is the energy stored in a 10 μF capacitor charged to 20 V?

a) 0.002 J b) 0.01 J c) 0.002 C d) 0.5 J

5.

What happens to the capacitance of a parallel-plate capacitor if the area of the plates is doubled and the separation is halved?

a) It is doubled b) It is quadrupled c) It is halved d) It is unchanged

6.

A parallel-plate capacitor is filled with a dielectric of constant k. What is the new capacitance compared to the original (vacuum) value?

a) k times larger b) k times smaller c) Unchanged d) Doubled

7.

Derivation: What is the equivalent capacitance of two capacitors, C1 and C2, connected in series?

a) C1 + C2 b) (C1 × C2)/(C1 + C2) c) C1 - C2 d) (C1 + C2)/2

8.

Which of the following best describes the effect of grounding one plate of a capacitor?

a) It increases the capacitance b) It brings that plate to zero potential c) It removes all charge from the plate d) It makes the field inside the capacitor zero

9.

Which of the following is true about the surface charge density on a conductor with a sharp point?

a) It is lower than on a flat surface b) It is the same as on a flat surface c) It is higher than on a flat surface d) It is always zero

10.

What is the potential difference across a 5 μF capacitor that stores 0.01 J of energy?

a) 20 V b) 40 V c) 63 V d) 100 V

11.

What is the surface charge density on a conductor if the electric field just outside is 2×10⁶ N/C?

a) 1.77×10⁻⁵ C/m² b) 3.54×10⁻⁵ C/m² c) 7.08×10⁻⁵ C/m² d) 1.77×10⁻⁴ C/m²

12.

What is the charge on a 8 μF capacitor connected to a 30 V battery?

a) 0.24 mC b) 0.48 mC c) 2.4 mC d) 24 mC

13.

Derivation: What is the capacitance of a parallel-plate capacitor with a dielectric of thickness t inserted between plates separated by distance d?

a) \( \varepsilon_0 A/(d-t+t/k) \) b) \( \varepsilon_0 A/(d-t) \) c) \( \varepsilon_0 A/(d+t/k) \) d) \( \varepsilon_0 A/(d+t) \)

14.

What happens to the capacitance of a parallel-plate capacitor if the area is tripled and the separation is doubled?

a) It is multiplied by 1.5 b) It is multiplied by 2 c) It is multiplied by 3 d) It is multiplied by 6

15.

Which of the following materials has the highest dielectric constant?

a) Air b) Glass c) Water d) Barium titanate

16.

Derivation: What is the electric field at a distance r from an infinitely long line of charge with linear charge density λ?

a) \( \lambda/(2\pi\varepsilon_0 r) \) b) \( \lambda/(4\pi\varepsilon_0 r) \) c) \( \lambda/(\pi\varepsilon_0 r) \) d) \( \lambda/(\varepsilon_0 r) \)

17.

Derivation: What is the electric potential at a distance r from a point charge Q?

a) \( Q/(4\pi\varepsilon_0 r) \) b) \( Q/(2\pi\varepsilon_0 r) \) c) \( Q/(\pi\varepsilon_0 r) \) d) \( Q/(\varepsilon_0 r) \)

18.

What is the energy stored in a 12 μF capacitor charged to 25 V?

a) 0.00375 J b) 0.0075 J c) 0.015 J d) 0.03 J

19.

Which of the following is true about the electric potential inside a conductor in electrostatic equilibrium?

a) It varies with position b) It is constant throughout c) It is maximum at the center d) It is zero everywhere

20.

What is the equivalent capacitance of a 4 μF and 8 μF capacitor connected in parallel?

a) 2.67 μF b) 4 μF c) 8 μF d) 12 μF

21.

Which of the following best describes the effect of a dielectric on the breakdown voltage of a capacitor?

a) It always increases the breakdown voltage b) It always decreases the breakdown voltage c) It has no effect on breakdown voltage d) It depends on the dielectric material

22.

What is the charge density on the plates of a parallel-plate capacitor with capacitance 6 μF, plate area 0.2 m², and voltage 50 V?

a) 1.5×10⁻⁶ C/m² b) 1.5×10⁻⁵ C/m² c) 1.5×10⁻⁴ C/m² d) 1.5×10⁻³ C/m²

23.

Three capacitors (3 μF, 6 μF, 9 μF) are connected in series. What is the equivalent capacitance?

a) 1.5 μF b) 1.8 μF c) 6 μF d) 18 μF

24.

Which of the following is true about the electric field between the plates of a charged parallel-plate capacitor?

a) It is uniform and directed from positive to negative plate b) It is non-uniform and strongest at the edges c) It is zero everywhere between the plates d) It varies sinusoidally with position

25.

What is the potential difference across a 25 μF capacitor that stores 0.125 J of energy?

a) 50 V b) 100 V c) 150 V d) 200 V

26.

Which of the following best describes the polarization of a dielectric in an electric field?

a) The dielectric becomes permanently charged b) The dielectric develops induced dipoles c) The dielectric becomes a conductor d) The dielectric loses all its electrons

27.

Derivation: What is the force between the plates of a parallel-plate capacitor with charge Q and plate area A?

a) Q²/(2ε₀A) b) Q²/(ε₀A) c) Q²/(4ε₀A) d) Q²/(8ε₀A)

28.

What happens to the electric field inside a capacitor when a dielectric is inserted?

a) It increases by a factor of k b) It decreases by a factor of k c) It remains unchanged d) It becomes zero

29.

What is the energy stored in a 16 μF capacitor charged to 30 V?

a) 0.0072 J b) 0.0144 J c) 0.072 J d) 0.144 J

30.

Which of the following is true about the surface charge density on a conductor?

a) It is uniform everywhere b) It is highest where the radius of curvature is smallest c) It is highest where the radius of curvature is largest d) It is always zero

Conductors, Capacitors, and Dielectrics Practice Test 2

30 New Questions – AP Physics C Level