Physics 2 Final Review

electri field diagrams = POSITIVE

+ charges repel outward from center

electric field diagrams = NEGATIVE

- charges attract towards center

A particular ion of oxygen is composed of 8 protons, 8 neutrons, and 9 electrons. In terms of the elementary charge 𝑒, what is the total charge of this ion?

-1e

Consider a scenario in which a point charge +𝑄 is located outside a closed surface represented by the dark circle in the figure. What is the net electric flux through the closed surface?

0

A charge travels from the positive terminal of a 6 V battery, through a light bulb, and through the battery back to the positive terminal. The total change in voltage experienced by the charge during this journey is

0 V

An infinitely long, solid, cylindrical conductor of radius 𝑅 carries current 𝐼. Which graph correctly shows the magnetic field strength inside and outside the conductor?

0 increase to Bmax and slow decrease to 3R

A pitching machine is programmed to pitch baseballs horizontally at a speed of 83 mph . The machine is mounted on a truck and aimed backward. As the truck drives away from a man at a speed of 55 mph , the machine shoots a ball towards him. Determine the correct relative speed for each object pair. The speed of the pitching machine relative to the truck

0 mph

he maximum change in a photon's energy when it undergoes Compton scattering occurs when its scattering angle is

180∘

What is the path length difference in thin film interference?

2 times the thin film thickness

A pitching machine is programmed to pitch baseballs horizontally at a speed of 83 mph . The machine is mounted on a truck and aimed backward. As the truck drives away from a man at a speed of 55 mph , the machine shoots a ball towards him. Determine the correct relative speed for each object pair. The speed of the pitched ball relative to the man

28 mph

Six copper wires have the listed lengths and cross‑sectional areas. The resistance 𝑅 of each segment can be calculated using 𝑅=𝜌𝐿/𝐴 where 𝜌 is the resistivity, 𝐿 is the length of the wire, and 𝐴 is the wire's cross‑sectional area. Rank the resistances of the wires from highest to lowest.

2L > L > L/2 A/2 > A > 2A

A pitching machine is programmed to pitch baseballs horizontally at a speed of 83 mph . The machine is mounted on a truck and aimed backward. As the truck drives away from a man at a speed of 55 mph , the machine shoots a ball towards him. Determine the correct relative speed for each object pair. The speed of the pitching machine relative to the man

55 mph

A pitching machine is programmed to pitch baseballs horizontally at a speed of 83 mph . The machine is mounted on a truck and aimed backward. As the truck drives away from a man at a speed of 55 mph , the machine shoots a ball towards him. Determine the correct relative speed for each object pair. The speed of the pitched ball relative to the truck

83 mph

The ray diagrams shown trace the path that light takes in order to locate the image formed by a concave mirror. Points 𝐶 and 𝑓 indicate the mirror's center of curvature and focal point, respectively. Identify which ray diagrams are drawn incorrectly.

A and C

You are holding a closed wire loop and moving through a room that has a uniform magnetic field that points from the floor toward the ceiling. Select the ways that can you orient the loop relative to the magnetic field so that the induced emf in the loop is zero. A. VERTICALLY, so it is aligned with the magnetic field B. HORIZONTALLY, so it is perpendicular to the magnetic field C. AT a constant angle between vertical and horizontal

A, B, C

Current 𝐼(𝑡) flows from point A to point B through an inductor coil, as shown in the figure. The current is decreasing with time. Which end of the inductor is at the higher potential ?

B

Current 𝐼(𝑡) flows from point B to point A through an inductor coil, as shown in the figure. The current is increasing with time. Which end of the inductor is at the higher potential?

B

The ray diagrams shown trace the path that light takes in order to locate the image formed by a concave mirror. Points 𝐶 and 𝑓 indicate the mirror's center of curvature and focal point, respectively. Identify which ray diagrams are drawn correctly.

B, D, E

The figures show snapshots of a rectangular loop as it passes from left to right through a region of constant magnetic field. The field points into the screen and is perpendicular to the plane of the loop. In which of the sequences is the magnetic flux through the loop decreasing?

D, leaving the magnetic field

A sphere with radius 𝑅 has a uniform surface charge density 𝜎 (charge per unit area). Use Gauss's law to find an expression for the magnitude E of the electric field at a radius 𝑟r from the center of the sphere, where 𝑟>𝑅 Your expression may include 𝑟, 𝑅, 𝜎, the permittivity of free space 𝜀0, and numerical constants.

E= 𝜎R^2 / 𝜀0 r^2

In hospitals with magnetic resonance‑imaging facilities and at other locations where large magnetic fields are present, there are usually signs warning people with pacemakers and other electronic medical devices not to enter. Why should people with implanted medical devices not enter locations with large magnetic fields?

Electronic medical devices moving in the presence of large magnetic fields experience large changes in magnetic flux. The resulting induced voltages and currents are large enough to interfere with the devices' operation.

A bicyclist rides at 𝑣B=8.0 m/s towards the north. A car is moving at 𝑣C=25 m/s, also towards the north, and is initially behind the rider. A truck is moving at 𝑣T=15 m/s towards the south, approaching the bicycle and the car.

Identify the diagram that correctly depicts the positions and velocities, relative to the ground, of the bicycle, car, and truck. B

Which correctly describes the behavior of an inductor in a circuit?

It opposes changes in the current.

In Maxwell's Equations, which of the following describes the equation ΦB = 0?

No magnetic monopoles have been discovered so far.

A circuit consists of two resistors connected in series with a power supply, as shown in the figure. The resistance of 𝑅1 is less than the resistance of 𝑅2. which resistor has the greatest voltage difference across it?

R2

A circuit consists of two resistors connected to a power supply in parallel, as shown in the figure. The resistance of 𝑅1 is greater than the resistance of 𝑅2. which resistor has the greater current flowing through it?

R2

A single, negative test charge is moved among the three points. Order the potential energy 𝑈 of the system when the test charge is at each point, from highest to lowest.

Ua > Ub> Uc

Two charges equal in magnitude but opposite in sign are placed on a plane. Three points, A, B, and C, are located as shown in the figure. Order the values of the electrical potential 𝑉 at points A, B, and C, from highest to lowest. highest potential --> lowest potential

Vc > Vb > Va

The diagrams show ray‑tracing techniques for locating the image formed by a convex lens. The points labeled 𝑓f indicate the lens's focal points. Select the correctly drawn ray diagrams.

a, d

A free negative charge released in an electric field will

accelerate in the direction in which the electric field is pointing

If two uncharged objects are rubbed together and one of them acquires a negative charge, then the other one

acquires a positive charge

The diagrams show ray‑tracing techniques for locating the image formed by a convex lens. The points labeled 𝑓f indicate the lens's focal points. Select the incorrectly drawn ray diagrams.

b, c, e

The figure shows a snapshot of an electromagnetic wave traveling into the screen in a straight line through empty space. The vertical arrow represents the electric field vector at that instant, and the horizontal arrow represents the magnetic field vector. At the time of this snapshot, the magnitudes of the electric and magnetic fields are at their respective maximum values for this particular wave. Which of the diagrams represent possible configurations of the electric and magnetic fields for this wave at some point in the future? Classify the images accordingly, assuming that the wave continues to travel into the screen unimpeded.

blue left red down

The figure depicts an electron in between the poles of an electromagnet. Explain how the electron is accelerated if the magnetic field is gradually being increased. The increase in magnitude of the magnetic field over time causes the electron to move

clockwise when viewed from above

If the number of turns per meter is doubled, the magnetic field will

double

True or False? heating a magnet makes it stronger

false

True or False? when two nearby electrons in a material have opposite spins, their contributions to the local magnetic field tend to add up

false

True or False? when a magnet is broken in half, you end up with a south pole magnet and a north pole manget

false

A permanent bar magnet with the north pole pointing downward is dropped through a solenoid, as shown in the illustration. What is the direction of the induced current that would be measured in the ammeter as the magnet falls completely through the solenoid?

first down, then up

If the magnet, still oriented with the north pole pointing downward, is pulled upward completely through the solenoid, what is the direction of the induced current measured in the ammeter?

first down, then up

Photons from which portion of the electromagnetic spectrum have the highest energy?

gamma ray

Consider four different types of electromagnetic radiation: radio waves, infrared, ultraviolet, and gamma rays. Arrange the types of radiation from the highest to the lowest energy.

gamma rays > UV> infrared > radio waves

Horizontally polarized light is to be passed through a sequence of three polarizing filters. The direction of the polarization axis for each filter is indicated by lines drawn parallel to the axis. One filter is oriented so that its polarization axis is vertical, another is horizontal, and the third is at an angle between horizontal and vertical. Place the three polarizers from left to right in the order that maximizes the amount of transmitted light.

incoming light entering from left to right --> horizontal parallel --> perpendicular --> vertical parallel

Gauss's law indicates that the flux through a closed surface

is proportional to the net charge enclosed

Suppose you cut a bar magnet into two pieces at the dashed line shown in the diagram, a bit closer to the north pole of magnet. After you cut the magnet into two pieces, which correctly describes the end of the smaller piece indicated with a point (•) in the diagram?

it will be a magnetic south pole.s

Which change to the conducting wires in a circuit will decrease the overall resistance of the wires?

make the wires thicker without changing their length

In the equation for electric current: i = nAev drif t, what does the quantity n represent?

number density in 1/m3

Peggy is an astronaut and volunteers for the first manned mission to Alpha Centauri, the nearest star system to the Solar System. Her spacecraft will travel at 80% of the speed of light, and the trip there and back will take over 10 years. Her twin sister Patty is an astronomer and will remain on Earth, studying Alpha Centauri using telescopes. When Peggy returns from her trip, how will their ages compare?

patty will be older than peggy

electric field diagrams +/-

positive charges repel from left to right towards - charge. negative charge attracted to itself

Consider four different types of electromagnetic radiation: radio waves, infrared, ultraviolet, and gamma rays. Arrange the types of radiation from the lowest to the highest frequency

radio waves > infrared > UV> gamma rays

Which diagram correctly indicates the direction of the electric field produced at each point by the positive charge?

same upward direction

The figure shows a snapshot of an electromagnetic wave traveling into the screen in a straight line through empty space. The vertical arrow represents the electric field vector at that instant, and the horizontal arrow represents the magnetic field vector. At the time of this snapshot, the magnitudes of the electric and magnetic fields are at their respective maximum values for this particular wave. Which of the diagrams represent possible configurations of the electric and magnetic fields for this wave at some point in the future? Classify the images accordingly, assuming that the wave continues to travel into the screen unimpeded.

short blue left short red down

In the circuit shown, the capacitor is fully charged when switch S is closed at time 𝑡=0 Consider the plots in Figures A through F. Which plot describes the energy stored by the capacitor (𝑈C) and inductor (𝑈L) as a function of time?

sine f(x) Figure A

A circuit consists of two resistors connected in series with a power supply, as shown in the figure. The resistance of 𝑅1 is less than the resistance of 𝑅2. which resistor has the greater current flowing through it?

the current through each resistor is the same

An RC circuit contains a constant source of EMF, a 100 Ω resistor, and a 9.00 mF capacitor, all connected in series. While testing the circuit, Vanya finds it takes the initially uncharged capacitor 0.624 seconds to reach half its maximum charge. If Vanya replaces the 100 Ω resistor with a 300 Ω resistor, what will happen to the time it takes to reach half the maximum charge on the capacitor?

the time will decrease

A circuit consists of two resistors connected to a power supply in parallel, as shown in the figure. The resistance of 𝑅1 is greater than the resistance of 𝑅2. which resistor has the greater voltage difference?

the voltage across each resistor is the same

A uniform electric field E~ points in the -z-direction. Which of the following surfaces is an equipotential surface? Drawing diagrams may help.

the xy-plane

Why do light rays refract at an interface between two different transparent materials?

their speed changes

In an RC circuit, the capacitor begins to discharge. In the region of space between the plates of the capacitor,

there are both electric and magnetic fields

You have two initially neutral insulating rods. You rub one with fur, and you rub the other with silk. When the rods are brought near each other, what happens?

there is a strong attraction

True or False opposite poles attract

true

True or False? magnetic domains are present even in an unmagnetized piece of iron

true

True or False? every electron in an atom behaves like a tiny magnet

true

True or false? dropping a magnet makes it weaker

true

For long‑distance transmission of power, in order to reduce losses in the wires by driving a low current at high voltage, the user should

use a step-up transformer

A square plane mirror of side length 𝑎 hangs on a wall such that its bottom edge is a height 𝑦y above the floor. The wall opposite the mirror is a distance 𝑤 away. Marco, whose eyes are at the exact height of the center of the mirror, stands directly in front of the mirror at the center of its width. Derive an expression for the maximum distance 𝑥 that Marco can stand from the mirror and still see the reflection of the bottom of the wall behind him. Assume that 𝑎<2𝑦.

x = aw/ 2y

An object that is glowing because of its temperature emits continuum radiation with a characteristic shape called a blackbody spectrum. Which of the choices shows the shape of a blackbody spectrum?

y-axis = intensity x-axis = wavelength at x=2 increase and parabola decrease to y=1