phy2112 final prep

Two identical loops of wire carry identical currents. Which arrow best represents the direction of the magnetic field at the point P midway between the loops?

e

Four resistors are connected across an 8-V DC battery as shown in the figure. The current through the 9-Ω resistor is closest to 

0.66A

A loop is inside a uniform, but NOT constant magnetic field pointing out the page as shown in the figure. If the induced current in the loop is clock wise then:  

The magnetic field is increasing

The refractive index of a medium is a measure of:

The degree to which light bends when it enters the medium from a vacuum.

What is the wavelength of the wave shown in the figure? 

2m

A proton and an electron are released from rest in the center of a capacitor (assume the capacitor is connected to a potential difference), which particle experience the largest acceleration. 

The electron

The figure shows three electric charges labeled Q1, Q2, Q3, and some electric field lines in the region surrounding the charges. What are the signs of the three charges? 

Q1 is positive, Q2 is negative, Q3 is positive. 

Resistors R1 and R2 NOT  identical, their actual values of resistance are unknown; which resistor dissipates more power?

The actual values of R1 and R2 are necessary to tell.

A conducting sphere of radius R carries an excess positive charge and is very far from any other charges. Which one of the following graphs best illustrates the potential (relative to infinity) produced by this sphere as a function of the distance r from the center of the sphere? 

D

The diagram shows a wire with an electric current ``I” coming out of the paper. In which direction would be the magnetic field at positions P1 and P2?

P1: left and P2: Up

In the figure, a straight wire carries a steady current I perpendicular to the plane of the page. A bar is in contact with a pair of circular rails, and rotates about the straight wire at a angular speed W. The direction of the induced current through the resistor R is:

There is no induced current

You are given two wind instruments of identical length. One is open at both ends, the second one is closed at one end. Which is able to produce the highest frequency sound?

The instrument that is open at both ends

In the figure, the inner loop carries a clockwise current I that is increasing. The resistor R is in the outer loop and both loops are in the same plane. The induced current through the resistor R is: 

a to b

An stationary ambulance’s siren emits a sound of frequency 1000 Hz An observer who is moving toward the siren with an unknown velocity will measure the siren  frequency (f)  for this sound such that 

f > 1000 Hz

The number of cycles completed by a wave per unit of time is known as: 

Frequency

Which statement is correct according to the circuit above?:

both 6 ohm are connected in parallel

all the top 2 ohm are connected in series

both 6 ohm and the 4ohm are connected in parallel

both 6 ohm and both top middle 2 ohm are connected in parallel

none of the above is correct

none of the above is correct

A Neutron is initially moving to the right when it enters a uniform electric field directed upwards. Which trajectory shown below will the neutron follow? 

W

A neutral metal bar is moving right at a constant velocity thought a region where there is a uniform magnetic field pointing inside the page. Which of the following diagrams best describe the charge distribution on the surface of the metal bar? 

d

A cone is resting on a tabletop as shown in the figure with its face horizontal. A uniform electric field of magnitude 4550 N/C points vertically upward. Which statement is correct

the flux magnitude on the face and on the sloping side are the same

the two fluxes are changing at a different rate so they cannot be determined

the flux magnitude on the face of the cone is larger since its area is larger

the flux magnitude on the face of the cone is smaller since its angle is sharper

the flux magnitude on the face of the cone is larger since its angle is wider

The flux magnitude on the face and on the sloping side are the same 

what is statement is correct about an AC circuit?:

AC stands for alternating current

the current in a circuit oscillates betweel a low and high value

the voltage in the circuit oscillates between a low and high value

the voltage and current can be in phase with eachother depending on the circuit configuration

all of the above are correct

all of the above are correct

The figure shows four Gaussian surfaces (labeled with letters) surrounding a distribution of charges. Which Gaussian surfaces have an electric flux of +q/ε0 through them

b

A particle with a NEGATIVE charge is placed at rest in a region of space where there is only a uniform electric filed. 

The particle will move in a linear path at a constant acceleration.

Four equal negative point charges are located at the corners of a square, their positions in the xy-plane being (1, 1), (-1, 1), (-1, -1), (1, -1). The electric field on the x-axis at (1, 0) points in the same direction as 

-X axis

When two or more capacitors are connected in parallel across a potential difference:

The potential difference across each capacitor is the same

A cylindrical wire has a resistance R and resistivity ρ. If its length and diameter are BOTH cut in half. What will be its new resistance?

2R

A cylindrical wire has a resistance R and resistivity ρ. If its length and diameter are BOTH cut in half. What will be its resistivity?

ρ

The picture below presents a sphere and an ellipsoid surrounding two different charges. Which statement is correct?:

The fluxes are equal beause the average radius and charge is the same

The flux in the sphere is larger because the charge is in the center

The flux in the sphere is larger because the charge enclosed is larger

The flux in the ellipsoid is larger becasue the outside area is larger

The flux in the ellipsoid is smaller because the eletric field will not always be parallel to the surface nromal, which is always the case for the sphere

The flux in the sphere is larger because the charge enclosed is larger

These two wave pulses travel along the same stretched string, one after the other. Which is true?:

VA > VB

VB >VA

VA = 0 and VB = 0

VA = VB

Not enough information to tell

VA = VB

When a certain string is under tension T=300 N, the speed of a wave in the string is v=235 m/s.  Later  the speed of a wave in the string if the tension is increased to T=350 N without changing the mass or length of the string? What statement is correct about v:

v > 235 m/s

v = 235 m/s

v < 235 m/s

v = -235 m/s

Not enough information to tell

v > 235 m/s

In the circuit shown in the figure, all the lightbulbs are identical. Which of the following is the correct ranking of the brightness of the bulbs?

A is the brightest, and B and C have equal brightness but less than A

Which statements are true for an electron moving in the direction of an electric field?

its electric potential energy increases as it goes from high to low

its potential energy increases as its kinetic energy decreases

its kinetic energy decreases as it moves in the direction of the electric field

all of them

none of them

all of them

When two point charges are a distance d part, the electric force that each one feels from the other has magnitude F. In order to make this force twice as strong, the distance would have to be changed to 

2d

2sqrt(2)

d/SQRT(2)

d/2

d/4

d/sqrt(2)

A rod attracts a positively charged hanging ball. The rod is:

Positive

Negative

Neutral

Either positive or neutral

either negative or neutral

either negative or neutral

Metal spheres 1 and 2 are touching. both are initially neutral. the charged rod is brought near. the charged rod is then removed. the spheres are esparated. afterward, the charges on the sphere are:

Q1 is 0 and Q2 is 0

Identical metal spheres are initially charged as shown.
Spheres P and Q are touched together and then separated.
Then spheres Q and R are touched together and separated.
Afterward the charge on
sphere R is

0nC

The charge on sphere 2 is twice that of sphere 1. Which vector below shows the force of 2 on 1

b

Which is the direction of the net force on the charge at the lower left

b

Why is this E field not possible?

This E-field is impossible because a uniformly charged rod must produce a purely radial electric field.
The drawn field has a component along the rod, violating symmetry and Gauss’s law.

Surfaces A and B have the same
shape and the same area. Which
has the larger electric flux?

C

Which surface, A or B, has the
larger electric flux?

Surface A has more flux

What if the charge is negative?

electron moving from negative to positive speeds up. electron moving from positive to negative slows down.

A and B are identical
lightbulbs connected to a
battery as shown. Which is
brighter?

The bulbs are equally bright

Compare the bulbs of A of circuit 1 and circuit 2. In which circuit is A brighter?

Circuit 1, Circuit B

The current in the fourth wire is:

2A to the left

If a bar magnet is cut in half, you end up with

C

Perform all 4 of the right hand rules and explain them!

Okay.

An induced current flows clockwise as
the metal bar is pushed to the right.
The magnetic field points

Into the screen.

Which loop has the larger
magnetic flux through it?

Loop B

The metal loop is being
pulled through a uniform
magnetic field. Is the
magnetic flux through
the loop changing?

No

The metal loop is rotating
in a uniform magnetic field.
Is the magnetic flux through
the loop changing?

Yes

The bar magnet is pushed toward the
center of a wire loop. What is the
direction of the induced current?

B

The current in the straight wire
is decreasing. Which is true?

There is a clockwise induced current in the loop.

The magnetic field is confined to the region inside the
dashed lines; it is zero outside. The metal loop is
being pulled out of the magnetic field. Which is true?

There is a clockwise induced current in the loop.

Imagine the magnetic field changes
according to the plot shown. The induced
emf around this loop is

0.02V