PHYS 212 : Engineering Physics II : Barber : Spring 2018 Final

The charge on a glass rod which has been rubbed with silk is called positive:

by arbitrary convention

When a hard rubber rod is given a negative charge by rubbing it with wool:

negative charges are transferred from wool to rod

Two electrons (e1 and e2) and an proton (p) lie on a straight line, as shown. The directions of the force of e2 on e1, the force of p on e1, and the total force on e1, respectively, are:

← → ←

An electrical insulator is a material:

through which electrons do not flow easily

A neutral metal ball is suspended by a string. A positively charged insulating rod is placed near the ball, which is observed to be attracted to the rod. This is because:

there is a rearrangement of the electrons in the ball

A positively charged metal sphere A is brought into contact with an uncharged metal sphere B. As a result:

both spheres are positively charged

As used in the definition of electric field, a "test charge":

none of the above

The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z). Then:

Y is positive and Z is negative

The diagram shows a particle with positive charge Q and a particle with charge Q. The electric field at point P on the perpendicular bisector of the line joining them is:

↑ up

Positive charge Q is uniformly distributed on a semicircular rod. What is the direction of the electric field at point P, the center of the semicircle?

→ right

An electron traveling north enters a region where the electric field is uniform and points north. The electron:

slows down

Two point charges are arranged as shown. In which region could a third charge +1 C be placed so that the net electrostatic force on it is zero?

I only

A point charge is placed at the center of a spherical Gaussian surface. The total electric flux ΦE through the closed surface is changed if:

the point charge is moved to just outside the sphere

Which of the following graphs represents the magnitude of the electric field as a function of the distance from the center of a solid charged conducting sphere of radius R?

[the graph that spikes then gradually dissipates]

A spherical conducting shell has charge Q. A particle with charge q is placed at the center of the cavity. The charge on the inner surface of the shell and the charge on the outer surface of the shell, respectively, are:

-q, Q+q

The electric field due to a uniform distribution of charge on a spherical shell is zero:

only inside the shell

Choose the INCORRECT statement:

If a closed surface encloses no charge, the electric field is zero everywhere on the surface

The cardboard center of a paper towel roll:

cannot be a Gaussian surface because it does not fully enclose a volume

An electron moves from point i to point f, in the direction of a uniform electric field. During this displacement:

the work done by the field is negative and the potential energy of the electron-field system increases

An electron volt is:

the energy gained by an electron in moving through a potential difference of 1 volt

The equipotential surfaces associated with a charged point particle are:

concentric spheres centered at the particle

In a certain region of space the electric potential increases uniformly from east to west and does not vary in any other direction. The electric field:

points east and does not vary with position

A hollow metal sphere is charged to a potential V. The potential at its center is:

V

Two conducting spheres, one having twice the diameter of the other, are separated by a distance large compared to their diameters. The smaller sphere (1) has charge q and the larger sphere (2) is uncharged. If the spheres are connected by a long thin wire:

1 and 2 have the same potential

A capacitor "has a charge Q". The actual charges on its plates are:

Q, -Q

If the charge on a parallel-plate capacitor is doubled:

the electric field is doubled

A 2-µF and a 1-µF capacitor are connected in parallel, and a potential difference is applied across the combination. The 2-µF capacitor has:

twice the charge of the 1-µF capacitor

Let Q denote charge, V denote potential difference, and U denote stored energy. Of these quantities, capacitors in series must have the same:

Q only

Capacitors C1 and C2 are connected in parallel. Their equivalent capacitance is given by:

C1*C2/(C1+C2)

A dielectric slab is slowly inserted between the plates of a parallel plate capacitor, while the potential difference between the plates is held constant by a battery. As it is being inserted:

the capacitance and the charge on the plate increase but the potential difference between the plates remains the same

A car battery is rated at 80 A-h. An ampere-hour is a unit of:

Charge

Conduction electrons move to the right in a certain wire. This indicates that:

The current density in electric field both point left

In a conductor carrying a current we expect the electron drift speed to be:

Much less than the average electron speed

The current is zero in a conductor when no potential difference is applied because:

For every electron with a given velocity there's another with a velocity of equal magnitude and opposite direction

Of the following choices, the copper conductor that has the least resistance is:

Thick short and cool

Which of the following graphs best represents the current-voltage relationship for a device that obeys Ohm's law?

Linear graph

"The sum of the emf's and potential differences around a closed loop equals zero" is a consequence of:

Conservation of energy

In the diagram R1 > R2 > R3. Rank the three resistors according to the current in them, least to greatest.

All are the same

The emf of a real battery is equal to the potential difference between its terminals:

Only when there is no current in the battery

"The sum of the currents into a junction equals the sum of the currents out of the junction" is a consequence of:

Conservation of charge

A battery is connected across a parallel combination of two identical resistors. If the potential difference across the terminals is V and the current in the battery is i, then:

The potential difference across each resistor is V and the current each resistor is i/2

The time constant RC has units of:

Seconds (none of the above)

In the formula {v:F} = q{v:v}x{v:B}...

F must be perpendicular to both v and B

An electron moves in the negative x direction, through a uniform magnetic field in the negative y direction. The magnetic force on the electron is:

In the negatives Z direction

A magnetic field exerts a force on a charged particle:

If the the particle is moving across the field lines

A magnetic field CANNOT:

Change the kinetic energy of a charge

The diagram shows a straight wire carrying a flow of electrons into the page. The wire is between the poles of a permanent magnet. The direction of the magnetic force exerted on the wire is:

Up

The diagrams show five possible orientations of a magnetic dipole {v:μ} in a uniform magnetic field {v:B}. For which of these does the magnetic torque on the dipole have the greatest magnitude?

graph pointing straight up

Electrons are going around a circle in a counterclockwise direction as shown. At the center of the circle they produce a magnetic field that is:

Into the page

Magnetic field lines produced by a long straight wire carrying a current:

Form circles concentric with the wire

In an overhead straight wire, the current is north. The magnetic field due to this current, at our point of observation, is:

West

A wire carrying a large current i from east to west is placed over an ordinary magnetic compass. The end of the compass needle marked "N" will point:

South

The magnetic field B inside a long ideal solenoid is independent of:

Cross-sectional area

Magnetic field lines inside the solenoid shown are:

Toward the top of the page

In the experiment shown:

There is a current in G just after S is opened or closed

Faraday's law states that an induced emf is proportional to:

The rate of change of the magnetic flux

A magnet moves inside a coil. Consider the following factors:

Strength of the magnet, number of turns in the coil, speed at which the magnet moves

A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:

Clockwise

A long straight wire is in the plane of a rectangular conducting loop. The straight wire carries an increasing current in the direction shown. The current in the rectangle is:

counterclockwise

The diagram shows an inductor that is part of a circuit. The direction of the emf induced in the inductor is indicated. Which of the following is possible?

The current is increasing and leftward

A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time, after t = 0, that the charge on the capacitor is a maximum is:

T/2

In an oscillating LC circuit, the total stored energy is U. The maximum energy stored in the capacitor during one cycle is:

U

The natural angular frequency of a certain RLC series circuit is ω₀. A source of sinusoidal emf, with angular frequency 2ω₀, is inserted into the circuit. After transients die out, the angular frequency of the current oscillations is:

2ω₀

In a purely resistive circuit the current:

Is in phase with the voltage

The rms value of an ac current is:

The steady current that produces the same rate of heating in a resistor

A step-down transformer is used to:

Increase the voltage

Displacement current exists wherever there is:

Changing electric field

The energy of a magnetic dipole in an external magnetic field is least when:

Dipole moment is parallel to the field

The magnetic properties of materials stem chiefly from:

Electron magnetic dipole moments

A magnetic field {v:B₀} is applied to a diamagnetic substance. In the interior, the magnetic field produced by the magnetic dipoles of the substance is:

less than B and in the opposite direction

The diagram shows two small paramagnetic spheres, one near each end of a bar magnet. Which of the following statements is true?

the forces on 1 and 2 are both toward the magnet

When a permanent magnet is strongly heated:

it loses its magnetism

Select the correct statement:

gamma rays have higher frequency than infra-red waves

Which of the following types of electromagnetic radiation travels at the greatest speed in vacuum?

All of these travel at the same speed

For an electromagnetic wave the direction of the vector {v:E}x{v:B} gives:

Direction of wave propagation

Three polarizing sheets are placed in a stack with the polarizing directions of the first and third perpendicular to each other. What angle could the polarizing direction of the middle sheet make with the polarizing direction of the first sheet to obtain zero transmitted intensity when unpolarized light is incident on the stack?

0

When light passes from air to glass, it bends:

Toward the normal and slows down

If n_water = 1.50 and n_glass = 1.33, then total internal reflection at an interface between this glass and water:

may occur whenever the light goes from water to glass

A virtual image is one:

From which light rays diverge but do not pass through

The term "virtual" as applied to an image made by a mirror means that the image:

Cannot be shown directly on the screen

When you stand in front of a plane mirror, your image is:

Virtual, upright, and the same size as you

The image produced by a convex mirror of an object in front of the mirror is always:

virtual, upright, smaller

A concave refracting surface is one with a center of curvature:

On the side of the incident light

An object placed outside the focal point of a converging lens will produce an image that is:

Inverted and real

Consider (I) the law of reflection and (II) the law of refraction. Huygens' principle can be used to derive:

Reflection and refraction

Interference of light is evidence that:

Light is a wave phenomenon

The reason there are two slits, rather than one, in a Young's experiment is:

To create a path length difference

In a Young's double-slit experiment the center of a bright fringe occurs wherever waves from the slits differ in the distance they travel by a multiple of:

A wavelengths

If two light waves are coherent:

Their phase difference is constant

Binoculars and microscopes are frequently made with coated optics by adding a thin layer of transparent material to the lens surface as shown. For minimum reflection of the incident light, one wants:

constructive interference between 3 and 4

Radio waves are readily diffracted around buildings whereas light waves are negligibly diffracted around buildings. This is because radio waves:

have much longer wavelengths than light waves

When a highly coherent beam of light is directed against a very fine wire, the shadow formed behind it is not just that of a single wire but rather looks like the shadow of several parallel wires. The explanation of this involves:

diffraction

The resolving power of a telescope can be increased by:

increasing the lens diameters

In the equation dsinθ= mλ for the lines of a diffraction grating, d is:

the grating spacing

A light beam incident on a diffraction grating consists of waves with two different wavelengths. The separation of the two first-order lines is great if:

the dispersion is great

Bragg's law for x-ray diffraction is 2dsinθ= mλ, where θ is the angle between the incident beam and:

a reflecting plane of atoms

Light from a stationary spaceship is observed, then the spaceship moves directly away from the observer at high speed. As a result, the light seen by the observer has:

a lower frequency and a longer wavelength than before

Which of the following electromagnetic radiations has photons with the greatest energy?

x-rays

In a photoelectric effect experiment the stopping potential is:

the electric potential that causes the electron current to vanish

Evidence for the wave nature of matter is:

electron diffraction and interference experiments