Q: A wire carrying a current of $$3 A is $$placed in a uniform magnetic field of $$0.5 T $$perpendicular to the wire. If the length of the wire in the field is $$2 m$$, what is the magnitude of the force on the wire?

$$F = I B L = 3 \times 0.5 \times 2 = 3 N$$

Q: According to Faraday's Law, what is the induced emf in a coil of $$100$$ turns if the magnetic flux through the coil changes by $$0.2 Wb in$$ $$0.01 s$$?

$$\text{emf} = -N \frac{\Delta \Phi}{\Delta t} = -100 \frac{0.2}{0.01} = -2000 V$$

Question 1

Which of the following best describes the difference between pitch and loudness in musical sound?

Accepted Answer

Pitch is determined by the frequency of the sound wave, while loudness is determined by its amplitude.

Question 2

A concert hall is designed to minimize standing waves for better acoustics. Which phenomenon is most responsible for the formation of standing waves?

Accepted Answer

Interference between incident and reflected sound waves.

Question 3

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

Accepted Answer

$$F = k \frac{q_1$ q_2$}{r^2$}$$

Question 4

A lightning bolt transfers $$30 C of $$charge in $$0.001 s. $$What is the average current during the strike?

Accepted Answer

$$I = \frac{Q}{t} = \frac{30}{0.001} = 30,000 A$$

Question 5

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have free electrons that can move easily throughout the lattice.

Question 6

A $$10 V $$battery is connected to a $$5$$ $$	ext{Ω}$$ resistor. What is the current through the resistor?

Accepted Answer

$$I = \frac{V}{R} = \frac{10}{5} = 2 A$$

Question 7

Which statement about magnetic fields is correct?

Accepted Answer

Magnetic field lines always form closed loops from north to south outside the magnet.

Question 8

A wire carrying a current of $$3 A is $$placed in a uniform magnetic field of $$0.5 T $$perpendicular to the wire. If the length of the wire in the field is $$2 m$$, what is the magnitude of the force on the wire?

Accepted Answer

$$F = I B L = 3 	imes 0.5 	imes 2 = 3 N$$

Question 9

According to Faraday's Law, what is the induced emf in a coil of $$100$$ turns if the magnetic flux through the coil changes by $$0.2 Wb in$$ $$0.01 s$$?

Accepted Answer

$$	ext{emf} = -N \frac{\Delta \Phi}{\Delta t} = -100 \frac{0.2}{0.01} = -2000 V$$

Question 10

Which of the following best describes electromagnetic induction?

Accepted Answer

The process by which a changing magnetic field creates an electric current in a conductor.

Question 11

Which equation gives the speed of light $$c in $$terms of the permittivity $$\$$varepsilon_0$$ and permeability $$\$$mu_0 of $$free space?

Accepted Answer

$$c = \frac{1}{\sqrt{\$$varepsilon_0$$ \mu_0$}}$$

Question 12

A ray of light 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?

Accepted Answer

$$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2$$ \Rightarrow \sin \$$theta_2$$ = \frac{$$n_1$$}{$$n_2$$} \sin \$$theta_1$$ = \frac{1.0}{1.33} \sin 30^\circ = 0.376 \Rightarrow \$$theta_2$$ \approx 22^\circ$$

Question 13

Why do objects appear smaller when viewed in a convex mirror?

Accepted Answer

Convex mirrors diverge light rays, causing the image to appear smaller and upright.

Question 14

A person stands $$2 m in $$front of a plane mirror. How far is the image from the person?

Accepted Answer

The image is $$2 m $$behind the mirror, so the total distance is $$2 + 2 = 4 m.$$

Question 15

Which of the following best explains why polarized sunglasses reduce glare?

Accepted Answer

They block horizontally polarized light reflected from surfaces, reducing glare.

Question 16

Which statement about the photoelectric effect is correct?

Accepted Answer

Electrons are emitted from a metal surface only if the incident light has a frequency above a certain threshold.

Question 17

A transformer has $$500$$ turns in the primary coil and $$100$$ turns in the secondary coil. If the input voltage is $$120 V$$, what is the output voltage?

Accepted Answer

$$V_s = V_p \frac{N_s}{N_p} = 120 \frac{100}{500} = 24 V$$

Physics Study Guide: Electricity, Magnetism, Sound, and Light

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