Electrostatics Practice Test

1.

Two point charges, +2 μC and -2 μC, are separated by 0.5 m in vacuum. What is the magnitude of the force between them? (k = 8.99 × 10⁹ N·m²/C²)

a) 0.14 N b) 0.23 N c) 0.36 N d) 1.44 N

2.

A point charge +Q is at the origin. What is the electric field at the point (0, a) due to this charge?

a) \( \frac{kQ}{a^2} \) in the +y direction b) \( \frac{kQ}{a^2} \) in the -y direction c) \( \frac{kQ}{a} \) in the +y direction d) \( \frac{kQ}{a^2} \) in the +x direction

3.

Two equal positive charges are placed 2 m apart. Where, along the line joining them, is the net electric field zero?

a) At the midpoint b) At infinity c) At a point outside the segment, beyond either charge d) There is no such point

4.

A thin ring of radius R has total charge Q uniformly distributed. What is the electric field at the center of the ring?

a) \( \frac{kQ}{R^2} \) b) 0 c) \( \frac{kQ}{2R^2} \) d) \( 2kQ/R^2 \)

5.

A conducting sphere of radius R carries a net charge Q. What is the electric field just outside its surface?

a) \( \frac{kQ}{R^2} \) b) \( \frac{kQ}{2R^2} \) c) 0 d) \( \frac{kQ}{R} \)

6.

Which of the following statements about electric potential is correct?

a) The potential is always zero at infinity b) The potential is a vector quantity c) The potential difference between two points is path-independent in electrostatics d) The potential is always positive

7.

A point charge +q is placed at the center of a hollow, uncharged conducting shell. What is the net charge induced on the inner surface of the shell?

a) 0 b) +q c) -q d) -2q

8.

Which of the following integrals gives the work required to move a charge q from point A to B in an electric field \( \vec{E} \)?

a) \( W = q \int_A^B \vec{E} \cdot d\vec{r} \) b) \( W = \int_A^B \vec{E} \cdot d\vec{r} \) c) \( W = \int_A^B q \, d\vec{r} \) d) \( W = \int_A^B \vec{E} \, dq \)

9.

Two charges, +Q and -Q, are separated by distance d. What is the electric field at the midpoint between them?

a) Zero b) \( \frac{4kQ}{d^2} \) directed from +Q to -Q c) \( \frac{2kQ}{d^2} \) directed from -Q to +Q d) \( \frac{kQ}{d^2} \) directed from +Q to -Q

10.

A thin, infinite plane of charge has surface charge density \( \sigma \). What is the magnitude of the electric field just above the plane?

a) \( \frac{\sigma}{2\varepsilon_0} \) b) \( \frac{\sigma}{\varepsilon_0} \) c) \( \frac{2\sigma}{\varepsilon_0} \) d) 0

11.

What happens to the net charge on an isolated conductor if it is grounded and then touched by a negatively charged rod?

a) It becomes positive b) It becomes negative c) It remains neutral d) It depends on the material

12.

Which of the following best describes the electric field just outside a charged conductor in electrostatic equilibrium?

a) It is perpendicular to the surface b) It is parallel to the surface c) It is zero d) It points radially inward

13.

Which of the following materials is an electrical insulator?

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

14.

What is the potential energy of a system of two point charges, +q and -q, separated by a distance d?

a) \( -\frac{kq^2}{d} \) b) \( \frac{kq^2}{d} \) c) 0 d) \( -\frac{kq^2}{2d} \)

15.

Which of the following is true for the electric field inside a conductor in electrostatic equilibrium?

a) It is always zero b) It is always nonzero c) It depends on the shape of the conductor d) It is maximum at the center

16.

What is the direction of the force on a negative charge placed in a uniform electric field?

a) In the direction of the field b) Opposite to the direction of the field c) Perpendicular to the field d) Zero

17.

Which of the following is a correct statement of Gauss's law?

a) The net electric flux through a closed surface is proportional to the enclosed charge b) The net electric field through a closed surface is always zero c) The net electric flux through an open surface is proportional to the enclosed charge d) The net electric field at the surface is proportional to the surface area

18.

Which of the following best describes the behavior of excess charge on a conductor?

a) It spreads evenly throughout the volume b) It accumulates at the center c) It resides entirely on the surface d) It is distributed randomly

19.

Which of the following is true about the energy stored in a capacitor?

a) \( U = \frac{1}{2}CV^2 \) b) \( U = CV \) c) \( U = \frac{1}{2}QV \) d) Both a and c

20.

A long, straight wire has a uniform linear charge density \( \lambda \). What is the magnitude of the electric field a distance r from the wire?

a) \( \frac{\lambda}{2\pi\varepsilon_0 r} \) b) \( \frac{\lambda}{4\pi\varepsilon_0 r^2} \) c) \( \frac{\lambda}{2\pi\varepsilon_0 r^2} \) d) \( \frac{\lambda}{\varepsilon_0 r} \)

21.

Two point charges, +3 μC and -3 μC, are placed 0.2 m apart. What is the magnitude of the force between them? (k = 9 × 10⁹ N·m²/C²)

a) 2.0 N b) 1.8 N c) 0.45 N d) 0.20 N

22.

What is the direction of the electric field at a point midway between two equal positive charges?

a) Toward the left charge b) Toward the right charge c) Perpendicular to the line joining the charges d) Zero

23.

A 2 μC charge is placed in a uniform electric field of 5000 N/C. What is the force on the charge?

a) 0.01 N b) 0.1 N c) 0.005 N d) 0.02 N

24.

Which statement is true about the electric potential at the center of a square with equal positive charges at each corner?

a) It is zero b) It is positive and greater than at the corners c) It is negative d) It is the same as at the corners

25.

What happens to the force between two point charges if the distance between them is tripled?

a) It becomes one-third as much b) It becomes one-ninth as much c) It triples d) It remains the same

26.

A 1 nC charge is moved 0.5 m parallel to a uniform electric field of 100 N/C. What is the work done by the field?

a) 5 × 10^-8 J b) 5 × 10^-7 J c) 5 × 10^-9 J d) 5 × 10^-6 J

27.

Which of the following best describes the electric field inside a hollow, uncharged, conducting shell?

a) It is zero everywhere inside b) It is maximum at the center c) It depends on the shell's thickness d) It is equal to the field outside the shell

28.

What is the net electric flux through a closed surface that encloses no net charge?

a) Zero b) Positive c) Negative d) Depends on the shape of the surface

29.

Which of the following actions will increase the capacitance of a parallel-plate capacitor?

a) Increasing the plate separation b) Decreasing the plate area c) Inserting a dielectric material d) Connecting the plates to ground

30.

Which statement is true about the electric field at the surface of a charged conductor?

a) It is always tangent to the surface b) It is always perpendicular to the surface c) It is always zero d) It points toward the center

Electrostatics Practice Test

30 Questions – AP Physics C Level