Question 1

Which of the following best describes the drift speed $$v_d of $$electrons in a conductor under the influence of an electric field?

Accepted Answer

It is the average velocity of electrons due to the applied electric field, given by $$v_d = \frac{eE	au}{m_e}.$$

Question 2

A copper wire has a cross-sectional area $$A$$ and carries a current $$I. $$Which equation correctly relates the current to the drift speed $$v_d$$ and the number density of electrons $$n_e$$?

Accepted Answer

$$I = n_e e v_d A$$

Question 3

Which statement about superconductors is correct?

Accepted Answer

Superconductors exhibit zero electrical resistance below a critical temperature.

Question 4

A battery supplies a potential difference $$\Delta V to a $$circuit with resistance $$R. $$What is the power dissipated by the resistor?

Accepted Answer

$$P = \frac{\Delta V^2$}{R}$$

Question 5

Which of the following is true for resistors connected in parallel?

Accepted Answer

The potential difference across each resistor is the same.

Question 6

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

Accepted Answer

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

Question 7

A charged particle with charge $$q$$ moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the magnitude of the force acting on the particle?

Accepted Answer

$$F = qvB$$

Question 8

Which of the following correctly expresses Ohm's Law for a conductor with constant cross-sectional area?

Accepted Answer

$$V = IR$$

Question 9

If the resistance of a wire is $$R = \rho \frac{L}{A}$$, which change will decrease the resistance?

Accepted Answer

Decrease the resistivity $$\rho.$$

Question 10

A circuit contains three resistors in series: $$R_1 = 2$$\,\Omega$$, R_2$ = 3\,\Omega$$, and $$R_3 = 5$$\,\Omega$$. What is the total resistance?

Accepted Answer

$$R_{total} = 10\,\Omega$$

Question 11

Which law states that the sum of currents entering a junction equals the sum of currents leaving the junction?

Accepted Answer

Kirchhoff's Junction Law

Question 12

A loop of wire with area $$A is $$placed in a changing magnetic field $$B. $$According to Faraday's Law, what is the induced emf in the loop?

Accepted Answer

$$\mathcal{E} = -\frac{d\Phi_B}{dt}$$

Question 13

What is the time constant $$	au$$ for an $$RL$$ circuit consisting of a resistor $$R$$ and an inductor $$L$$?

Accepted Answer

$$	au = \frac{L}{R}$$

Question 14

A charged particle moves in a circle of radius $$r in a $$uniform magnetic field $$B. $$What is the angular frequency $$\omega of $$its motion?

Accepted Answer

$$\omega = \frac{qB}{m}$$

Question 15

Which of the following is true about the magnetic field produced by a current-carrying wire?

Accepted Answer

The magnetic field lines form concentric circles around the wire.

Question 16

If two parallel wires carry currents in the same direction, what is the nature of the force between them?

Accepted Answer

The wires attract each other.

Question 17

What is the SI unit of inductance?

Accepted Answer

Henry (H)

Question 18

A capacitor in an LC circuit oscillates with a frequency $$f. $$What is the relationship between $$f$$, the inductance $$L$$, and the capacitance $$C$$?

Accepted Answer

$$f = \frac{1}{2\pi \sqrt{LC}}$$

Question 19

Which of the following best describes the right-hand rule for the direction of the magnetic force on a moving charge?

Accepted Answer

Point your thumb in the direction of velocity, fingers in the direction of the magnetic field; the force is perpendicular to your palm.

Study Notes: Current, Resistance, DC Circuits, Magnetic Fields, and Electromagnetic Induction

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