Q: A circuit contains a $$10\ \Omega$$ resistor and a $$20\ \Omega$$ resistor in parallel. What is the equivalent resistance?

$$\frac{1}{R_{\text{eq}}} = \frac{1}{10} + \frac{1}{20} \Rightarrow R_{\text{eq}} = 6.67\ \Omega$$

Q: A $$5\ \mu\text{F}$$ capacitor is charged to $$10\ \text{V}. $$What is the energy stored in the capacitor? (Use $$U = \frac{1}{2}CV^2$)

$$2.5 \times 10$$^{-4}$$\ \text{J}$$

Question 1

Which of the following best describes the relationship between electric field $$\vec{E}$$ and electric potential $$V in a $$region of space?

Accepted Answer

The electric field is the gradient of the electric potential: $$\vec{E} = -
abla V$$

Question 2

A parallel plate capacitor is connected to a battery of voltage $$V. If $$the distance between the plates is doubled while keeping the charge constant, what happens to the electric field between the plates?

Accepted Answer

The electric field remains the same.

Question 3

Which equation correctly expresses Ohm's Law for a resistor in a direct current circuit?

Accepted Answer

$$V = IR$$

Question 4

A wire of length $$L$$ and resistance $$R is $$cut into two equal pieces. What is the resistance of each piece?

Accepted Answer

$$R/2$$

Question 5

A charged particle moves perpendicular to a uniform magnetic field $$\vec{B}. $$What is the shape of its trajectory?

Accepted Answer

A circle

Question 6

Which of the following best explains why electromagnetic waves can travel through a vacuum?

Accepted Answer

They do not require a medium because changing electric and magnetic fields propagate each other.

Question 7

A light ray passes from air ($$n=1.0) $$into water ($$n=1.33) at an $$angle of $$30^\circ to $$the normal. What is the angle of refraction in the water? (Use Snell's Law: $$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2)$$

Accepted Answer

$$22.1^\circ$$

Question 8

Which of the following statements about capacitors in series is correct?

Accepted Answer

The total capacitance is less than any individual capacitance: $$\frac{1}{C_{	ext{eq}}} = \sum \frac{1}{C_i}$$

Question 9

A transformer is used to step up the voltage from $$120\ 	ext{V} to$$ $$480\ 	ext{V}. If $$the primary coil has $$100$$ turns, how many turns must the secondary coil have? (Use $$\frac{V_s}{V_p} = \frac{N_s}{N_p})$$

Accepted Answer

400

Question 10

Which phenomenon explains the colorful patterns seen in a thin film of oil on water?

Accepted Answer

Interference of light waves

Question 11

A circuit contains a $$10\ \Omega$$ resistor and a $$20\ \Omega$$ resistor in parallel. What is the equivalent resistance?

Accepted Answer

$$\frac{1}{R_{	ext{eq}}} = \frac{1}{10} + \frac{1}{20} \Rightarrow R_{	ext{eq}} = 6.67\ \Omega$$

Question 12

Which of the following is true about the speed of light in different media?

Accepted Answer

Light travels slower in glass than in air.

Question 13

A coil of wire is placed in a changing magnetic field. Which law describes the induced emf in the coil?

Accepted Answer

Faraday's Law: $$\mathcal{E} = -\frac{d\Phi_B}{dt}$$

Question 14

Which property of light is responsible for sunglasses reducing glare from horizontal surfaces?

Accepted Answer

Polarization

Question 15

A $$5\ \mu	ext{F}$$ capacitor is charged to $$10\ 	ext{V}. $$What is the energy stored in the capacitor? (Use $$U = \frac{1}{2}CV^2$)

Accepted Answer

$$2.5 	imes 10$$^{-4}$$\ 	ext{J}$$

Question 16

Which of the following best describes the function of a lens in an optical instrument?

Accepted Answer

It refracts light to form an image at a specific location.

Question 17

A $$60\ 	ext{W}$$ light bulb operates at $$120\ 	ext{V}. $$What is the current through the bulb? (Use $$P = IV)$$

Accepted Answer

$$0.5\ 	ext{A}$$

Question 18

Which statement about electromagnetic waves is correct?

Accepted Answer

They consist of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation.

Question 19

A student uses a diffraction grating to measure the wavelength of a laser. If the first-order maximum occurs at an angle $$	heta$$ and the grating spacing is $$d$$, which equation should be used?

Accepted Answer

$$d \sin 	heta = m \lambda$$

PHY 2054: Physics Without Calculus II – Electricity, Magnetism, and Optics (Study Guide)

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