Q: A household circuit contains a resistor of $$10\,\Omega$$ connected to a $$120\,\text{V}$$ power supply. What is the current flowing through the resistor?

$$I = \frac{120}{10} = 12\,\text{A}$$

Q: A wire carries a current of $$5\,\text{A}$$ and is placed in a uniform magnetic field of $$0.2\,\text{T}$$ perpendicular to the wire. If the wire is $$0.5\,\text{m}$$ long, what is the magnitude of the force on the wire?

$$F = I B l = 5 \times 0.2 \times 0.5 = 0.5\,\text{N}$$

Question 1

A lightning strike is a real-world example of charge separation and potential difference. Which of the following best explains why lightning occurs?

Accepted Answer

Lightning occurs when charge separation in clouds creates a large potential difference between the cloud and ground, causing a rapid discharge of electrons.

Question 2

Which equation represents Coulomb's Law for the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

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

Question 3

A household circuit contains a resistor of $$10\,\Omega$$ connected to a $$120\,	ext{V}$$ power supply. What is the current flowing through the resistor?

Accepted Answer

$$I = \frac{120}{10} = 12\,	ext{A}$$

Question 4

Which law is used to calculate the electric field produced by a symmetric charge distribution, such as a charged sphere?

Accepted Answer

Gauss's Law

Question 5

A parallel plate capacitor is charged to a voltage $$V. If $$the plates are moved farther apart while keeping the charge constant, what happens to the capacitance and the stored energy?

Accepted Answer

Capacitance decreases, stored energy increases.

Question 6

Which equation expresses Ohm's Law, relating voltage $$V$$, current $$I$$, and resistance $$R$$?

Accepted Answer

$$V = IR$$

Question 7

A wire carries a current of $$5\,	ext{A}$$ and is placed in a uniform magnetic field of $$0.2\,	ext{T}$$ perpendicular to the wire. If the wire is $$0.5\,	ext{m}$$ long, what is the magnitude of the force on the wire?

Accepted Answer

$$F = I B l = 5 	imes 0.2 	imes 0.5 = 0.5\,	ext{N}$$

Question 8

Which of the following best describes Lenz's Law?

Accepted Answer

The induced current in a circuit always flows in the direction that opposes the change in magnetic flux.

Question 9

Which equation represents the speed of light $$c in $$terms of the permittivity $$\$$epsilon_0$$ and permeability $$\$$mu_0 of $$free space?

Accepted Answer

$$c = \frac{1}{\sqrt{\$$epsilon_0$$ \mu_0$}}$$

Question 10

A ray of light passes from air ($$n_1 = 1.0$) into water (n_2$ = 1.33) at an $$angle of $$30^\circ to $$the normal. What is the angle of refraction in water?

Accepted Answer

$$\$$theta_2$$ = \arcsin\left(\frac{n_1$}{n_2$} \sin \$$theta_1$$\right) = \arcsin\left(\frac{1.0}{1.33} \sin 30^\circ\right) \approx 22^\circ$$

Question 11

Which of the following is a correct statement of Faraday's Law of electromagnetic induction?

Accepted Answer

The induced emf in a circuit is equal to the negative rate of change of magnetic flux through the circuit.

Question 12

A thin convex lens has a focal length of $$10\,	ext{cm}. An $$object is placed $$30\,	ext{cm}$$ from the lens. What is the image distance?

Accepted Answer

$$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i} \Rightarrow d_i = \frac{1}{\frac{1}{f} - \frac{1}{d_o}} = \frac{1}{\frac{1}{10} - \frac{1}{30}} = 15\,	ext{cm}$$

Question 13

Which of the following is NOT a property of electromagnetic waves?

Accepted Answer

They require a medium to propagate.

Question 14

A diffraction pattern is observed when light passes through a single slit. Which equation gives the position of the first minimum on a screen at distance $$L$$ from the slit of width $$a$$?

Accepted Answer

$$a \sin 	heta = \lambda$$

Question 15

Which of the following is a correct statement of Ampere's Law?

Accepted Answer

$$\oint \vec{B} \cdot d\vec{l} = \mu_0$ I_{enc}$$

Question 16

A circuit contains a resistor ($$R$$), a capacitor ($$C$$), and an AC voltage source. Which of the following best describes the phase relationship between the voltage across the capacitor and the current?

Accepted Answer

The voltage across the capacitor lags the current by $$90^\circ.$$

Question 17

Which of the following is a correct statement of the law of reflection?

Accepted Answer

The angle of incidence equals the angle of reflection.

Question 18

A real-world example: A television broadcast uses electromagnetic waves. Which property of electromagnetic waves allows the signal to travel from the transmitter to your home without a physical medium?

Accepted Answer

Electromagnetic waves can travel through a vacuum.

Question 19

Which of the following is a correct statement of the principle of superposition as applied to electric fields?

Accepted Answer

The total electric field at a point is the sum of the electric fields due to each charge.

PHYS 299: Introduction to Electricity, Magnetism, and Light – Course Overview and Study Guide

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