Physics Final Exam Multiple choice

The resistance of a wire is

A) proportional to its length and its cross-sectional area.

B) proportional to its length and inversely proportional to its cross-sectional area.

C) inversely proportional to its length and proportional to its cross-sectional area.

D) inversely proportional to its length and its cross-sectional area.

B) proportional to its length and inversely proportional to its cross-sectional area.

The resistivity of a wire depends on

A) its length.

B) its cross-sectional area.

C) the material out of which it is composed.

D) all of the given answers

C) the material out of which it is composed.

If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit will

A) increase by a factor of two.

B) increase by a factor of four.

C) decrease to one-half its original value.

D) decrease to one-fourth its original value.

C) decrease to one-half its original value.

A total of 2.0 × 1013 protons pass a given point in 15 s. What is the current?

A) 1.3 mA

B) 1.3 A

C) 0.21 nA

D) 0.21 μA

D) 0.21 μA

A 12-V battery is connected to a 100-Ω resistor. How many electrons flow through the wire in 1.0 min?

A) 1.5 × 1019

B) 2.5 × 1019

C) 3.5 × 1019

D) 4.5 × 1019

D) 4.5 × 1019

How much does it cost to operate a 25-W soldering iron for 8.0 hours, if energy costs $0.08/kWh?

A) $0.016

B) $0.25

C) $0.16

D) $1.50

A) $0.016

A negatively charged rod is brought near one end of an uncharged metal bar. The end of the metal bar farthest from the charged rod will be charged

A) positive.

B) negative.

C) neutral.

D) none of the given answers

B) negative.

8. Two charged objects are separated by a distance d. The first charge is larger in magnitude than the second charge.

A) The first charge exerts a larger force on the second charge.

B) The second charge exerts a larger force on the first charge.

C) The charges exert forces on each other equal in magnitude and opposite in direction.

D) The charges exert forces on each other equal in magnitude and pointing in the same direction.

C) The charges exert forces on each other equal in magnitude and opposite in direction.

A 40.0-W light bulb (average power) is plugged into a European AC outlet with a 𝑉 = 230 V.

9. What is the rms Current?

A) 174 mA

B) 246 mA

C) 123 mA

D) What, no Rufus question?

A) 174 mA

10. What is the value for the average current? (Note: I0 is peak current)

A) Zero

B) 𝐼0√2

C) 𝐼0/√2

D) I0

A) Zero

Three identical capacitors are connected in parallel to a potential source. If a charge of Q flows into this combination, how much charge does each capacitor carry?

A) 9Q

B) 3Q

C) Q

D) Q/3

E) Q/9

D) Q/3

A 6.00 Ω and a 12.0 Ω resistor are connected in parallel across an ideal 36 V battery. What power is

dissipated by the 6.00 Ω resistor?

A) 48.0 W

B) 216 W

C) 492 W

D) 24.0 W

E) 96.0 W

B) 216 W

A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in series with the first one, the time constant of the new RC circuit will be:

A) the same as before.

B) larger than before.

C) smaller than before.

D) variable with time.

C) smaller than before.

A 7.0 Ω resistor is connected across the terminals of a battery having an EMF of 10 V. If a 0.50 A current flows, what is the internal resistance of the battery?

A) 13 Ω

B) 20 Ω

C) 10.8 Ω

D) 27.0 Ω

E) 18 Ω

A) 13 Ω

A 2.0 x 10-6 F capacitor is charged to 12 V and then discharged through a 4.0 x 106 Ω resistor. How long will it take for the voltage across the capacitor to drop to 3.0 V?

A) 8.0 s

B) 35 s

C) 22 s

D) 24 s

E) 11 s

E) 11 s

A straight bar magnet initially has a north pole on the right and the south pole on the left. If you cut this magnet in half, then the right half will:

A) contain only a north pole.

B) contain a north pole on the right and a south pole on the left.

C) contain a north pole on the left and a south pole on the right.

D) contain only a south pole.

E) no longer contain any poles.

B) contain a north pole on the right and a south pole on the left.

At a particular instant, an electron moves toward the East in a uniform magnetic field that is directed straight downward (i.e. toward the center of Earth). The magnetic force that acts on it is:

A) upward.

B) downward.

C) toward the North.

D) toward the South.

E) zero.

D) toward the South.

Two long, parallel wires are 0.400 m apart and carry currents of 4.00 A and 6.00 A. What is the magnitude of the force per unit length that each wire exerts on the other wire?

A) 2.00 μN/m

B) 5.00 μN/m

C) 12.0 μN/m

D) 16.0 μN/m

E) 38.0 μN/m

C) 12.0 μN/m

A coil of wire containing N turns is in an external magnetic field that is perpendicular to the plane of the coil and it steadily changing. Under these circumstances, an EMF ε is induced in the coil. If the rate of change of the magnetic field and the number of turns in the coil are now doubled (but nothing else is changed), what will be the new induced EMF in the coil?

A) 4ε

B) 2ε

C) ε

D) ε/2

E) ε/4

A) 4ε

A coil lies flat on a table in a region where a magnetic field is pointing up. The magnetic field vanishes

suddenly. When viewed from above, what is the sense of the induced current in the coil as the field fades?

A) The induced current flows clockwise.

B) The induced current flows counterclockwise.

C) There is no induced current in this coil.

D) The current flows clockwise initially, and then flows counterclockwise before stopping.

B) The induced current flows counterclockwise

A transformer is a device used to:

A) transform an alternating current into a direct current.

B) transform a direct current into an alternating current.

C) increase or decrease an ac voltage.

D) increase or decrease a dc voltage.

C) increase or decrease an ac voltage.

An ideal step-up transformer doubles a primary voltage of 110 V. What is the ratio of the number of turns in its primary coil to the number of turns in the secondary coil?

A) 1:4

B) 4:1

C) 2:1

D) 1:2

E) 1:8

D) 1:2

The primary of an ideal transformer has 100 turns and its secondary has 200 turns. Neglecting frictional losses, if the power input to the primary is 100 W, we can expect the power output of the secondary to be

A) 50 W.

B) 100 W.

C) 200 W.

D) none of the given answers.

B) 100 W.

When a certain string is under tension T, the speed of a wave in the string is v. What will be the speed of a

wave in the string if the tension is increased to 2T without changing the mass or length of the string?

A) v/2

B) v/ rad 2

C) v Rad 2

D) 2v

E) 4v

C) v Rad 2

A guitar string is set into vibration with a frequency of 512 Hz. How many oscillations does it undergo each minute?

A) 30,700

B) 8.53

C) 26.8

D) 1610

E) 512

A) 30,700

The lowest tone to resonate in a pipe of length L that is closed at one end but open at the other end is 200

Hz. Which one of the following frequencies will not resonate in that pipe?

A) 200 Hz

B) 400 Hz

C) 600 Hz

D) 1000 Hz

E) 1400 Hz

B) 400 Hz

Which one of the following is not an electromagnetic wave?

A) ultraviolet

B) infrared

C) radio waves

D) sound waves

E) gamma rays

D) sound waves

In an electromagnetic wave in free space, the electric and magnetic fields are

A) parallel to one another and perpendicular to the direction of wave propagation.

B) parallel to one another and parallel to the direction of wave propagation.

C) perpendicular to one another and perpendicular to the direction of wave propagation.

D) perpendicular to one another and parallel to the direction of wave propagation.

C) perpendicular to one another and perpendicular to the direction of wave propagation.

Which one of the following types of electromagnetic wave travels through space the fastest?

A) radio waves

B) infrared

C) ultraviolet

D) microwaves

E) They all travel through space at the same speed.

E) They all travel through space at the same speed.

A certain part of the electromagnetic spectrum ranges from 200 nm to 400 nm. What is the highest frequency associated with this portion of the spectrum? (c = 3.00 × 108 m/s)

A) 1.50 × 1014 Hz

B) 7.50 × 1013 Hz

C) 7.50 × 1014 Hz

D) 7.50 × 1015 Hz

E) 1.50 × 1015 Hz

E) 1.50 × 1015 Hz