Physics Exam #2

Front 1

Consider two capacitors with unequal capacitance connected in parallel to a battery. Which of the following statements are true?

Back 1

The voltage across each of the capacitors is the same.

The sum of the charge stored on each capacitor is equal to the charge supplied by the battery.

The equivalent capacitance of the combination is greater than the capacitance of either of the capacitors.

Front 2

Consider three resistors with unequal resistances connected in parallel to a battery. Which of the following statements are true?

Back 2

The voltage across each of the resistors is the same and is equal in magnitude to the voltage of the battery.

The algebraic sum of the currents flowing through each of the three resistors is equal to the current supplied by the battery.

The equivalent resistance of the combination of resistors is less than the resistance of any one of the three resistors.

Front 3

Consider three resistors with unequal resistances connected in series to a battery. Which of the following statements are true?

Back 3

The equivalent resistance of the combination of resistors is greater than the resistance of any one of the three resistors.

The algebraic sum of the voltages across the three resistors is equal to the voltage supplied by the battery.

The current flowing through each of the resistors is the same and is equal to the current supplied by the battery.

Front 4

The junction rule describes the conservation of which quantity? Note that this rule applies only to circuits that are in a steady state.

Back 4

Current

Front 5

Apply the junction rule to the junction labeled with the number 1 (at the bottom of the resistor of resistance R2).Answer in terms of given quantities, together with the meter readings I1 and I2 and the current I3.

Back 5

ΣI=0= = I1−I2−I3

Front 6

Apply the loop rule to loop 2 (the smaller loop on the right). Sum the voltage changes across each circuit element around this loop going in the direction of the arrow. Remember that the current meter is ideal.Express the voltage drops in terms of Vb, I2, I3, the given resistances, and any other given quantities.

Back 6

Σ(ΔV)=0= = I2R2−I3R3

Front 7

Now apply the loop rule to loop 1 (the larger loop spanning the entire circuit). Sum the voltage changes across each circuit element around this loop going in the direction of the arrow.Express the voltage drops in terms of Vb, I1, I3, the given resistances, and any other given quantities.

Back 7

Σ(ΔV)=0= = I1R1+I3R3−Vb

Front 8

Select the expressions that will be equal to the voltage of the battery in the circuit, where VA, for example, is the potential drop across resistor A.

Back 8

VA+VB

VA+VC

VD

Front 9

A bar magnet is oriented perpendicular to a uniform magnetic field as shown in(Figure 1) . Describe the force and/or torque on the magnet.

Back 9

There is a net torque on the magnet in a counterclockwise direction.

Front 10

Two concentric loops of wire are carrying currents in opposite directions as shown in (Figure 2) . Describe the net force and the torque on either of the current loops.

Back 10

There is a net force on each loop that causes them to repel each other.

Front 11

Which of the following statements are true?

Back 11

Earth's geographic north pole is actually a magnetic south pole.

The north pole of a bar magnet will attract the south pole of another bar magnet.

The south poles of two bar magnets will repel each other.

Front 12

Which of the following statements are true concerning the creation of magnetic fields?

Back 12

A moving electric charge creates a magnetic field at all points in the surrounding region.

A permanent magnet creates a magnetic field at all points in the surrounding region.

An electric current in a conductor creates a magnetic field at all points in the surrounding region.

Front 13

In the figure, a conducting rod is shown moving in a uniform magnetic field . Which of the following statements are true?

Back 13

The magnitude of the potential difference in the rod is proportional to the velocity v of the rod.

An electric field is established in the rod directed from point a to point b.

The free charges in the rod are acted upon by a magnetic force.

The magnitude of the potential difference in the rod is proportional to the strength of the magnetic field.

Front 14

A conducting rod is being dragged along conducting rails, as shown in (Figure 1) . The magnetic field is directed out of the screen. In what direction does the induced current flow through the light bulb?

Back 14

The induced current flows through the bulb from the right to the left.

Front 15

A circular loop of conducting wire is moving through a uniform magnetic field, as shown in(Figure 2) . Is a non-zero emf induced in the loop?

Back 15

No

Front 16

Two loops of wire, each having a different radius, encircle an infinitely long solenoid, as shown in (Figure 3) . The magnetic field B⃗ is zero outside the solenoid. The current through the solenoid is increasing with time, causing the magnetic field inside the solenoid to increase with time. Which statement is true?

Back 16

The emf around the two wire loops is the same and is non-zero.

Front 17

A circular loop of wire lies flat on a level table top in a region where the magnetic field vector points straight upward. The magnetic field suddenly vanishes. As viewed from above, in what direction does the induced current flow in the loop of wire?

Back 17

An induced current flows counterclockwise in the loop of wire.

Front 18

In the figure, a conducting rod is shown moving to the right along U-shaped conducting rails. The apparatus is in a uniform magnetic field perpendicular to the plane of the figure. As viewed from above, in what direction does the induced current flow in the U-shaped apparatus?

Back 18

An induced current flows counterclockwise in the U-shaped apparatus.

Front 19

Which of the following statements are true regarding transformers?

Back 19

A transformer is used to increase or decrease an alternating current voltage.

In a transformer, if the secondary coil contains more loops than the primary coil, then it is a step-up transformer.

Front 20

A resistor, an inductor, and a switch are all connected in series to an ideal battery of constant terminal voltage. Suppose at first the switch is open, and then, at some initial time t = 0, it is closed. Which of the following statements are true?

Back 20

At the instant the switch is closed, the current begins to increase at a rate that depends upon the value of the inductance of the inductor.

The steady-state value of the current depends on the resistance of the resistor.

Front 21

A resistor, an inductor, and a capacitor are connected in series to an AC source. What is the condition for resonance to occur?

Back 21

The capacitive reactance must be equal to the inductive reactance.

Front 22

Which of the following statements are true concerning electromagnetic waves in a vacuum?

Back 22

When electromagnetic waves travel in vacuum, there is a definite, constant ratio between the magnitudes of the electric and magnetic fields.

Electromagnetic waves travel in a vacuum with a definite and unchanging speed.

Front 23

Which of the following statements are true concerning electromagnetic radiation fields?

Back 23

The magnetic field at any point is perpendicular to the direction of wave travel.

The electric and magnetic fields are in phase with each other as they propagate through space.

The electric field at any point is perpendicular to the direction of wave travel.

Front 24

Which of the following statements are true?

Back 24

A time-varying magnetic field will produce an electric field.

A time-varying electric field will produce a magnetic field.

Front 25

Consider the electromagnetic field produced at a given distance from a light source. Which of the following statements are true?

Back 25

The intensity of the wave is proportional to the speed of light.

The intensity of the wave is proportional to the square of the fields.

Front 26

Which of the following statements are true?

Back 26

Electromagnetic waves transport linear momentum.

Electromagnetic waves transport energy from one region of space to another.

Electromagnetic waves can exert pressure on an object.

Front 27

Consider two copper wires of equal cross-sectional area. One wire has 3 times the length of the other. How do the resistances of these two wires compare?

Back 27

The longer wire has 3 times the resistance of the shorter wire.

Front 28

Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions,

Back 28

the wires push away from each other.

Front 29

Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the length of the solenoid becomes twice as long (to 2L), but all other quantities remained the same, the magnetic field inside the solenoid will

Back 29

become one-half as strong as initially.

Front 30

An ac generator consisting of a coil with N turns rotating at angular speed ω in an external magnetic field B produces a maximum emf ε0.If you now decrease the number of turns in the coil to N/2 and at the same time cause it to rotate twice as fast, what will be the new maximum emf if you do not change any of the other quantities?

Back 30

ε0

Front 31

A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held above the center of the coil with its south pole downward. The magnet and the coil are now both raised upward with the same velocities. As viewed from above, what is the direction of the current induced in the coil as the magnet approaches the coil?

Back 31

No current is induced in the coil.