Question 1

A point charge $$q is $$placed at the center of a conducting spherical shell of inner radius $$R_1$$ and outer radius $$R_2. $$What is the electric field at a distance $$r$$ from the center, where $$R_1$$ \u003c r \u003c $$R_2$$?

Accepted Answer

$$E = \frac{q}{4\pi\$$epsilon_0$$ r^2$}$$

Question 2

Two point charges $$+Q$$ and $$-Q$$ are placed at a distance $$2a$$ apart. What is the electric potential at the midpoint between them?

Accepted Answer

$$V = 0$$

Question 3

A parallel plate capacitor is filled with a dielectric of dielectric constant $$k. If $$the original capacitance is $$C_0$$, what is the new capacitance?

Accepted Answer

$$C = k C_0$

Question 4

A charged particle moves in a uniform magnetic field perpendicular to its velocity. What is the shape of its trajectory?

Accepted Answer

Circle

Question 5

The resistance of a wire is $$R. If $$its length is doubled and its cross-sectional area is halved, what is the new resistance?

Accepted Answer

$$R' = 4R$$

Question 6

A capacitor of capacitance $$C is $$charged to a potential $$V$$ and then disconnected from the battery. If a dielectric of constant $$k is $$inserted, what is the new potential across the capacitor?

Accepted Answer

$$V' = \frac{V}{k}$$

Question 7

Which of the following is the correct expression for the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r in $$vacuum?

Accepted Answer

$$F = \frac{1}{4\pi\$$epsilon_0$$} \frac{q_1$ q_2$}{r^2$}$$

Question 8

A wire of resistance $$R is $$bent into a circle. What is the resistance between two diametrically opposite points?

Accepted Answer

$$R/4$$

Question 9

A solenoid of length $$l$$, area $$A$$, and $$N$$ turns carries a current $$I. $$What is the magnetic field inside the solenoid?

Accepted Answer

$$B = \mu_0$ \frac{N}{l} I$$

Question 10

A charged particle of mass $$m$$ and charge $$q$$ enters a region with electric field $$E$$ and magnetic field $$B$$ perpendicular to each other. If the velocity of the particle is $$v = \frac{E}{B}$$, what is the net force on the particle?

Accepted Answer

$$F = 0$$

Question 11

A resistor of resistance $$R$$ and a capacitor of capacitance $$C$$ are connected in series to a battery of emf $$V. $$What is the time constant of the circuit?

Accepted Answer

$$	au = RC$$

Question 12

A current $$I$$ flows through a long straight wire. What is the magnetic field at a distance $$r$$ from the wire?

Accepted Answer

$$B = \frac{\mu_0$ I}{2\pi r}$$

Question 13

A parallel plate capacitor has plates of area $$A$$ separated by distance $$d. $$What is the capacitance?

Accepted Answer

$$C = \frac{\$$epsilon_0$$ A}{d}$$

Question 14

A charged ring of radius $$R$$ carries a total charge $$Q. $$What is the electric field at the center of the ring?

Accepted Answer

$$E = 0$$

Question 15

A battery of emf $$E$$ and internal resistance $$r is $$connected to an external resistance $$R. $$What is the current in the circuit?

Accepted Answer

$$I = \frac{E}{R + r}$$

Question 16

A charged particle moves in a circle of radius $$r in a $$uniform magnetic field $$B. $$What is the frequency of revolution?

Accepted Answer

$$f = \frac{qB}{2\pi m}$$

Question 17

A capacitor is charged to a potential $$V$$ and then disconnected from the battery. If the plates are moved farther apart, what happens to the energy stored in the capacitor?

Accepted Answer

It increases

Question 18

A wire of length $$L$$ and resistance $$R is $$cut into $$n$$ equal pieces. These pieces are connected in parallel. What is the equivalent resistance?

Accepted Answer

$$R_{eq} = \frac{R}{n^2$}$$

Question 19

A charged particle is released from rest in a uniform electric field. What is its acceleration?

Accepted Answer

$$a = \frac{qE}{m}$$

Question 20

A spherical conductor of radius $$R$$ carries a charge $$Q. $$What is the electric field just outside its surface?

Accepted Answer

$$E = \frac{Q}{4\pi\$$epsilon_0$$ R^2$}$$

Electrostatics, Capacitors, and DC Circuits: Key Concepts and Practice

Study Guide - Practice Questions

Study Guide - Flashcards