Physics Exam 2 - RQs & Chapter Quizzes

T/F: A light emitting diode has the property that the potential difference between its ends is approximately 1.5V when it conducts currents raging from 1mA to 50mA. This device is ohmic.

False

T/F: Resistivity of a wire depends on a shape of a wire.

False

T/F: Two long parallel wires 10.0 cm apart each carry current of 3.0 A in the opposite direction. The magnetic field at the point midway between the wires is zero.

False

∆V=IR is valid for all the materials and all the devices known to a human.

False (this is Ohm's Law)

For the situation shown in Figure 17.10, the following statements compare the potential (V) or the current (I) among the marked points A, B, C, D. Which are true? (Choose all that apply.)' a) V at C is larger than V at D. b) I at C is larger than I at D. c) I at C equals I at D. d) V at C equals V at D.

a & c a) V at C is larger than V at D. c) I at C equals I at D.

A light bulb is connected to a battery so that current flows through it and it lights up. For example, the light bulb could be the resistor in the circuit of figure 17.9. Which of the following would increase the amount of power used by the light bulb (i.e. make it brighter)? Choose all that apply. a) Add another battery in series with the first one. b) Cut the wire at a point after the current goes through the battery, so more is "used up." c) Add another battery in parallel with the first one. d) Increase the light bulb's resistance. e) Decrease the light bulb's resistance.

a & e a) Add another battery in series with the first one. e) Decrease the light bulb's resistance.

Electrical charges and magnetic poles have many similarities, but one difference is: a) opposite magnetic poles repel. b) one magnetic pole cannot create magnetic poles in other materials. c) a magnetic pole cannot be isolated. d) magnetic poles do not produce magnetic fields.

a magnetic pole cannot be isolated.

Resistors of values 7 Ω, 15 Ω, and 25 Ω are connected in parallel across a fresh battery. Which resistor dissipates the greatest power? a) 7 Ω b) 15 Ω c) 25 Ω d) All dissipate the same power when in parallel.

a) 7 Ω

Which of the following best describes the inner workings of conductors? a) Electrons collide at random, experiencing a net change of position equal to zero, except when exposed to an external electric field. b) The electrons start at one electrode and travel directly to the other electrode, stopping there. c) The electrons' drift speed depends only on the material of the conductor and not on the voltage difference applied to it. d) None of the above.

a) Electrons collide at random, experiencing a net change of position equal to zero, except when exposed to an external electric field.

A magnet approaches a loop of wire as shown in Figure 20.4. Which option best describes the magnetic flux through this loop? a) Flux is nonzero and increasing. b) Flux is nonzero and decreasing. c) Flux is nonzero but not changing. d) Flux is zero and not changing.

a) Flux is nonzero and increasing.

What must the initial state of motion of a charged particle be if it will follow a helical path in a magnetic field? a) It must be moving at an angle that is neither parallel to nor perpendicular to the magnetic field. b) It must be moving parallel to the magnetic field. c) It must be moving parallel to the magnetic field. d) It must be moving in the direction opposite to the magnetic field. e) It must be initially at rest when it is placed in the magnetic field.

a) It must be moving at an angle that is neither parallel to nor perpendicular to the magnetic field.

At the moment the switch closes on this freshly connected RC circuit (SEE RQ18.3, #2): a) Q = 0, I = ε/R b) Q = Cε, I = 0 c) Q = Cε, I= ε/R d) Q = 0, I = 0

a) Q = 0, I = ε/R

A conductor of radius r, length L and resistivity 𝜌 has resistance R. It is melted down and formed into a new conductor, also cylindrical, with one fourth the length of the original conductor. The resistance of the new conductor is a) R/16 b) R/4 c) R d) 4R e) 16R

a) R/16

A simple circuit consists of resistor R, capacitor C charged to a potential difference V and a switch that is initially open but then thrown closed. Immediately after the switch is thrown closed, the current in the circuit is a) V0/R b) zero c) infinite d) need more info

a) V0/R

Consider two identical resistors wired in a series. If there is an electric current through the combination, the current in the second resistor, when compared to the current in the first resistor is a) equal to b) half c) smaller than, but not necessarily half d) zero

a) equal to

Complete the following statement: The sum of the magnitudes of the currents directed into a junction a) equals the sum of the magnitudes of the currents directed out of the junction. b) is less than the total current directed out of the junction. c) equals the current that is directed along one of the lines out of the junction. d) is divided equally among the number of lines directed out of the junction. e) is greater than the total current directed out of the junction.

a) equals the sum of the magnitudes of the currents directed out of the junction.

Cosmic rays (atomic nuclei stripped bare of their electrons) would continously bombard Earth's surface if most of them were not deflected by Earth's magnetic field. Given that Earth is, to an excellent approximation, a magnetic dipole, the intensity of cosmic rays bombarding its surface is greatest at the a) poles b) mid-latitudes c) equator d) it is the same everywhere

a) poles

On a computer chip, two conducting strips carry charge from P to Q and from R to S. If the current direction is reversed in both wires, the net magnetic force of strip 1 on strip 2 a) remains the same b) reverses c) changes in magnitude, but not direction d) changes to some other direction

a) remains the same

CAN'T UPLOAD IMAGE BUT THIS IS Ch. 17 Quiz, #9 An ammeter A is connected between points a and b in the circuit shown below, in which the four resistors are identical. The current through the ammeter is a) 1/2 b) 1/4 c) zero d) infinite

c) zero

You are facing a circular loop of wire, and move a magnet towards this loop (with south pole closer to the loop, north pole closer to you). As a result... a) you see a current moving clockwise around the wire. b) you see a current moving counterclockwise around the wire. c) there is no current in the wire.

a) you see a current moving clockwise around the wire.

Rank each situation from the highest to the lowest current in the +x direction (i.e. a large current in +x direction would rank highest, a large current in -x direction would rank lowest). a) Every second, 1000 ions with charge +e move past you heading to the right. b) Every second, 1000 ions with charge +e and 500 ions with charge -e move past you heading to the right. c) Every second, 1000 ions with charge +e and 1000 ions with charge -e move past you heading to the right. d) Every second, 500 ions with charge +e move past you heading to the right, and 300 ions with charge -e move past you heading to the left. e) Every second, 1000 ions with charge -e move past you heading to the right.

a, d, b, c, e a) Every second, 1000 ions with charge +e move past you heading to the right. d) Every second, 500 ions with charge +e move past you heading to the right, and 300 ions with charge -e move past you heading to the left. b) Every second, 1000 ions with charge +e and 500 ions with charge -e move past you heading to the right. c) Every second, 1000 ions with charge +e and 1000 ions with charge -e move past you heading to the right. e) Every second, 1000 ions with charge -e move past you heading to the right.

At t = 0, the switch in an RLcircuit in Figure 20.26 is closed. At that moment, a. I = 0, εL = -ε b. I = 0, εL = 0 c. I = ε/R, εL = ε d. I = ε/R, εL = 0

a. I = 0, εL = -ε

How does the current Imeasured at the time equal to one time constant after the switch in the RL circuit is closed, compare to the maximum current Imax ? a. I>Imax/2 b. I=Imax/2 c. I<Imax/2 d. Without knowing R and L, this cannot be determined.

a. I>Imax/2

In a circuit made up of inductor, resistance, ammeter, battery and switch in series, at which of the following times after the switch is closed is the rate of current increase greatest? a. at zero b. at one time constant c. at reciprocal of one time constant d. at ten times the time constant.

a. at zero

Magnetic Declination for a location near Baltimore is approximately a) 12˚ E b) 12˚ W c) 0˚ d) 20˚ E e) 20˚ W

b) 12˚ W

Two parallel wires carry currents in the same direction and exert a force on each of magnitude F for each meter of length. One of the currents is now reversed in direction and doubled in magnitude. What are the resulting magnitude for the force per meter of length and its direction relative to the wires? a) 2F, attractive b) 2F, repulsive c) 4F, attractive, d) 4F, repulsive

b) 2F, repulsive

The basic function of an electromotive force (emf) in a circuit is to do which of the following? a) Convert electrical energy into some other form of energy. b) Convert some other form of energy into electrical energy. c) Both choices (a) and (b) are valid. d) None of the above choices are valid.

b) Convert some other form of energy into electrical energy.

In the figure 18.15a (see textbook) one can identify a) one loop b) two loops c) three loops d) four loops

c) three loops

Two rectangular loops of wire lie in the same plane, as shown in the figure. If the current in the outer loop is counterclockwise and increases with time, what is true of the current induced in the inner loop? a) It is zero. b) It is clockwise. c) It is counterclockwise. d) Its direction depends on the dimensions of the loops.

b) It is clockwise.

If the rotating coil used in a generator has its radius doubled, what change results in the amplitude of the voltage produced? a) It doubles. b) It quadruples. c) It changes by a factor 2^(3/2).

b) It quadruples.

Light bulb A is rated at 60 W and light bulb B is rated at 100 W. Both are designed to operate at 110 V. Which statement is correct? a) The 60 W bulb has a greater resistance and greater current than the 100 W bulb. b) The 60 W bulb has a greater resistance and smaller current than the 100 W bulb. c) The 60 W bulb has a smaller resistance and smaller current than the 100 W bulb. d) The 60 W bulb has a smaller resistance and greater current than the 100 W bulb. e) We need to know the resistivities of the filaments to answer this question.

b) The 60 W bulb has a greater resistance and smaller current than the 100 W bulb.

An uncharged, series RC circuit is connected across a battery. For which situation will the time for the capacitor to reach 90% of its final charge remain unchanged?​ a) The RC time constant is doubled. b) The battery voltage is doubled. c) A second resistor is added in series with the original resistor. d) All of these situations result in the time for the capacitor to reach 90% of its final charge to change.

b) The battery voltage is doubled.

A rectangular loop is placed near a long wire carrying current as shown in figure. If the current decreases with time, what can be said of the current induced in the loop? (SEE IMAGE FROM Ch. 20 Quiz, #5 - wire is horizontal with current pointing left, loop is higher up on the page) a) The current has a direction that depends on a size of the loop. b) The current is clockwise. c) The current is counterclockwise. d) The current is zero.

b) The current is clockwise.

Suppose a long, straight wire carries a current upwards. A short distance directly east of the wire, a negatively charge particle is moving upwards parallel to the wire. In what direction is the magnetic force on the particle? a) The force is upwards. b) The force is eastward. c) The force is westward. d) Either there is no force or its direction is not given among these choices.

b) The force is eastward.

A rectangular loop is placed in a uniform magnetic field with the plane of the loop parallel to the direction of the field. If a current is made to flow through the loop in the direction shown by the arrows, the field exerts on the loop: a) a net force b) a net torque c) a net torque and a net force. d) neither a net force nor a net torque.

b) a net torque

"Motional emf" is best described as... a) the motion of a battery. b) a potential difference between ends of a conductor moving through a magnetic field. c) the process inside a battery that causes current to flow. d) the motion of any object through a magnetic field caused by an induced emf

b) a potential difference between ends of a conductor moving through a magnetic field.

Three resistors, each of different value, are used in a circuit with a power source supplying 12 volts. For which of the following resistor combinations is the total power supplied the greatest? a) all three resistors in series b) all three resistors in parallel c) two of the resistors in parallel with the third resistor in series with the parallel pair d) This cannot be found until it is known which resistor is in series with the parallel pair.

b) all three resistors in parallel

As more resistors are added in series, the equivalent resistance of the circuit approaches infinity. In contrast, as more resistors are added in parallel, the equivalent resistance, Ω, a) approaches infinity b) approaches zero c) becomes zero d) approaches 1Ω

b) approaches zero

A charged particle accelerated to a velocity v enters the chamber of a mass spectrometer. The particle's velocity is perpendicular to the direction of the uniform magnetic field B in the chamber. After the particle enters the magnetic field, its path is a a) parabola b) circle c) spiral d) straight line

b) circle

Kirchhoff's loop rule is equivalent to which of the following principles? a) conservation of charge b) conservation of energy c) conservation of force d) conservation of mass

b) conservation of energy

When a magnetic field causes a charged particle to move in a circular path, the only quantity listed below which the magnetic force changes significantly as the particle goes around in a circle is the particle's: a) energy b) linear momentum c) speed d) radius of the circle e) time to go around the circle once.

b) linear momentum

Which of the following best describes superconductors? a) materials that have less than half the resistivity of iron b) materials with essentially no resistance below a critical temperature, peculiar to each material c) materials which have a drop in their resistivity as their temperatures are lowered d) Conductors are materials which are very useful in a variety of ways; hence the name "superconductor."

b) materials with essentially no resistance below a critical temperature, peculiar to each material

A particle of positive charge q travels with velocity v towards the top of the screen. The magnetic field present, B, points rightward. The force a) points leftward b) points into the screen c) points toward the bottom of the screen d) points out of the screen

b) points into the screen

A current in a solenoid coil creates a magnetic field inside that coil. The field strength is directly proportional to: a) the coil area b) the current c) Both choices and are valid. d) Neither choice is valid

b) the current

A straight wire of length is oriented east-west and is in a magnetic field B pointing north. The wire is falling towards ground at a constant speed v. Which end of the rod is positively charged? a) neither b) the east end c) the west end d) both ends

b) the east end.

In which situation(s) is there an induced current in a loop of wire? a) The flux through the loop is zero and not changing. b) The flux through the loop is zero but increasing. c) The flux through the loop is nonzero and not changing. d) The flux through the loop is nonzero and decreasing. e) The flux through the loop is nonzero and increasing.

b, d, & e

A long straight wire carries a steady current I. A rectangular conducting loop lies in the same plane as the wire (below it), with two sides parallel to the wire and two sides perpendicular. Suppose the loop is pushed upward toward the wire. Given the direction of I (to the right), the induced current in the loop is a. clockwise b. counterclockwise c. current is zero d. need more information

b. counterclockwise

When the number of turns in a solenoid and its length are both doubled, the ratio of the magnitude of the new magnetic field inside to the magnitude of the original magnetic field inside is a) 1/4 b) 1/2 c) 1 d) 2 e) 4

c) 1

Square coil A has 2N turns and sides of length L, and square coil B has N turns and sides of length 2L. When a current of 2 amps is sent through coil A and a current of 1 amp is sent through coil B, which coil has the greater magnetic moment? a) coil A b) coil B c) Both have the same magnetic moment. d) Need more info

c) Both have the same magnetic moment.

Three resistors connected in series each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the system made up of the three resistors in series? a) IT = I1 + I2 + I3 b) IT = (1/I1 + 1/I2 +1/ I3) c) IT = I1 =I2 =I3 d) IT = (1/I1 + 1/I2 +1/ I3)^-1

c) IT = I1 =I2 =I3

Which is (are) true? The magnetic dipole moment of a current loop a) is proportional to the area enclosed by the loop. b) is proportional to the current in the loop. c) all of the above d) none of the above

c) all of the above

Charge flows through a light bulb. Suppose a wire of negligable resistance is connected in parallel with the wire. When the wire of negligible resistance is connected, a) all the charge continue to flow through the bulb. b) half the charge flows through the wire, the other half continues through the bulb. c) all the charge flows through the wire. d) none of the above.

c) all the charge flows through the wire.

As more identical resistors are added in parallel to a circuit, the total resistance in the circuit a) increases b) remains the same c) decreases

c) decreases

In a circuit made up of inductor L, resistance R, ammeter, DC battery and switch in series, the current is greatest at which of the following times, as measured after the switch is closed? a) zero. b) one time constant. c) at a time t = L/R d) ten time constants.

d) ten time constants.

Which statement regarding the force of a magnetic field on a current-carrying wire is true?​ a) The magnetic force on the wire is independent of the direction of the current. b) The force on the wire is directed parallel to both the wire and the magnetic field. c) The force takes its largest value when the magnetic field is parallel to the wire. d) All of the above statements are false.

d) All of the above statements are false.

The battery powering a light bulb is disconnected. As the light bulb's heat dissipates, how will the resistance and current change? a) The resistance will decrease and the current will increase. b) The resistance will increase and the current will be zero. c) The resistance will increase and the current will decrease. d) The resistance will decrease and the current will be zero

d) The resistance will decrease and the current will be zero

A current in a long, straight wire produces a magnetic field. The magnetic field lines: a) go out from the wire to infinity. b) come in from infinity to the wire. c) form circles that pass through the wire. d) form circles that go around the wire.

d) form circles that go around the wire.

The internal resistances of an ideal voltmeter and an ideal ammeter are respectively (ideal meaning the behavior of the system is not changed when using the meter): a) zero and zero b) infinite and infinite c) zero and infinite d) infinite and zero

d) infinite and zero

The flux of the magnetic field caused by an induced current in a loop a) is in the same direction as the flux causing the induced current. b) is in the opposite direction to the flux causing the induced current. c) is in the same direction as the change in flux causing the induced current. d) is in the opposite direction to the change in flux causing the induced current.

d) is in the opposite direction to the change in flux causing the induced current.

A rectangular loop is placed in a uniform magnetic field with the plane of the loop perpendicular to the direction of the field. If a current is made to flow through the loop in the direction shown by the arrows, the field exerts on the loop: a) a net force b) a net torque c) a net torque and a net force. d) neither a net force nor a net torque.

d) neither a net force nor a net torque.

Electricity may be generated by rotating a loop of wire between the poles of a magnet. The induced current is greatest when a) the plane of the loop is parallel to the magnetic field. b) the plane of the loop is perpendicular to the magnetic field. c) the magnetic flux through the loop is at maximum. d) the plane of the loop makes an angle of 45° with the magnetic field.

d) the plane of the loop is parallel to the magnetic field.

When does a charging capacitor stop charging? a) when the amount of charge on the two plates is equal b) when the potential difference across the plates of the capacitor is equal to zero volts c) when the amount of charge on the two plates is infinitely large d) when the potential difference across the plates of the capacitor is equal to the emf of the battery e) when all of the charge available in the circuit has been forced to collect on the plates of the capacitor

d) when the potential difference across the plates of the capacitor is equal to the emf of the battery

A particle of charge q travels with velocity v in the same direction as the magnetic field, B. What is the force exerted on the charge? a) qvB, in the direction of the magnetic field b) qvB, in the direction opposite that of the magnetic field c) qvB, in a direction perpendicular to the magnetic field and the velocity d) zero

d) zero

The self-inductance of a solenoid increases under which of the following conditions? a. Only the solenoid length is increased b. Only the cross sectional area is decreased. c. Only the number of coils per unit length is decreased. d. Only the number of turns is increased.

d. Only the number of turns is increased.

A bar magnet is dropped from above and falls through the loop of wire. The north pole of the magnet points downwards towards the ground as it falls. Which statement is correct? a. The current in the loop always flows in a clockwise direction. b. The current in the loop always flows in a counterclockwise direction. c. The current in the loop is clockwise as the magnet approaches the loop, then it is counterclockwise after it has passed through the loop. d. The current in the loop is counterclockwise as the magnet approaches the loop, then it is clockwise after it has passed through the loop. e. No current flows in the loop because both ends of the magnet move through the loop.

d. The current in the loop is counterclockwise as the magnet approaches the loop, then it is clockwise after it has passed through the loop.

A circuit consists of a lightbulb connected to two conducting rails and a conducting movable bar, as shown in the figure. An external magnetic field is directed perpendicular to the plane of the circuit. During which of the following actions will the bulb light up? (FOR IMAGE SEE Ch. 20 Quiz, #4) a) The bar is moved to the left. b) The bar is moved to the right. c) The magnitude of the magnetic field increases with time. d) The magnitude of the magnetic field decreases with time. e) All of the above. f) None of the above.

e) All of the above.

Appliances with three-pronged plugs compared to those with two-prong plugs are a) safer to use and connected to ground. b) no safer to use and ungrounded. c) more dangerous to use and connected to ground. d) safer to use and ungrounded.

safer to use and connected to ground.

You have 2 circuits, each with identical batteries and 2 identical lightbulbs. In one, the lightbulbs are in parallel; in the other, they are in series. Which circuit puts out more light?

the parallel circuit (Note: Light output is directly proportional to power dissipated)