Physics Midterm

0.50 kO

What resistance should be added in series with a 1.0 H inductor to complete an RL circuit with a 2.0 ms time constant? 0.50 k Ω 0.50 Ω 0.69 Ω 2.0 Ω

500

The resistors in the circuit shown in the figure each have a resistance of 500 Ω. What is the equivalent resistance of the circuit? A. 1000 B. 125 C. 2000 D. 500

zero

Three charges shown in the figure form an equilateral triangle with 8.9 cm long sides. What is the electric potential at the point indicated with the dot? zero 700 V 350 V 1000 V

-2200 N/C

2.4 m Two point charges, Q1 = -3 μC and Q2 = +4 μC, are placed as shown. In the figure, the y-component of the electric field, at the origin O, is closest to: zero 2200 N/C 1.1×104 N/C −1.1×104 N/C -2200 N/C

3.1 V

A 10 V battery is connected across two resistors in series. If the resistors have resistances of 730 Ω and 330 Ω, what is the voltage drop across the 330 Ω resistor? A. 3.1 V B. 6.9 V C. 22 V D. 4.5 V

7.1 MV

A 2.1 μC negative point charge has a positively charged object in a elliptical orbit about it. If the mass of the positively charged object is 1.0 kg and the distance varies from 2 mm to 8 mm between the charges, what is the maximum potential difference through which the positive object moves? 7.1 MV 2.4 MV 12 MV -3.2 MV

0.0083 um

A 300 pF capacitor consists of two circular plates of radius 0.3 mm. How far apart are the plates? (The value of εo is 8.85 × 10-12 C2/N∙m2.) 0.00047 μm 0.00094 μm 0.0042 μm 0.0083 μm

2.25 H

A 4 A current passes through an inductor. If the inductor stores 18 J of energy, what is the inductance? 72 H 144 H 2.25 H 3 H

4 nJ

A 4 μC negative charge is attracted to a large, well-anchored, positive charge. How much kinetic energy does the negatively charged object gain if the potential difference through which it moves is 1 mV? 4 nJ 0.25 kJ 4 μJ 0.25 J

1.3

A 5 meter length of wire carrying a current of 5 A lies on a horizontal table with a rectangular top of dimensions 0.300 m× 0.400 m. The ends of the wire are attached to opposite ends of a diagonal of the rectangle. A vertical magnetic field of 0.5 T is present. What magnetic force acts on this segment of wire? A 5 meter length of wire carrying a current of 5 lies on a horizontal table with a rectangular top of dimensions 0.300 0.400 . The ends of the wire are attached to opposite ends of a diagonal of the rectangle. A vertical magnetic field of 0.5 is present. What magnetic force acts on this segment of wire? 1.8 N 1.3 N Zero 13 N The force cannot be determined without knowing the shape of the length of wire.

1.9x10^9

A 5.9 × 1014 Hz laser emits a 3.3 μs pulse, 5.0 mm in diameter, with a beam energy density of 0.23 J/m3. The number of wavelengths in the length of the beam is closest to: 1.9×10^10 1.9×10^9 5.8×10^9 5.8×10^8 5.8×10^10

0.3 N

A 50 g insulating sphere carries a charge Q = -60 μC and is suspended by a silk thread from a fixed point. An external electric field which is uniform and vertical is applied. In the situation above, the applied electric field has a magnitude of 3000 N/c and is directed downward. The tension in the thread is closest to: 0.7 N 0.5 N 0.2 N 0.4 N 0.3 N

243 nm

A 8.43 × 1014 Hz electromagnetic wave propagates in carbon tetrachloride with a speed of 2.05 × 108 m/s. The wavelength of the wave in carbon tetrachloride is closest to: 356 nm 302 nm 323 nm 270 nm 243 nm

The current at A is equal to the current at B, which is equal to the current at C, which is equal to the current at D

A 9 Volt battery is hooked up to two resistors in series. One has a resistance of 5 Ohms, and the other has a resistance of 10 Ohms. Several locations along the circuit are marked with letters, as shown in the figure. Which statement about this circuit is true? - The current at A is greater than the current at B, which is equal to the current at C, which is greater than the current at D. - The current at A is greater than the current at B, which is greater than the current at C, which is greater than the current at D. - The current at A is equal to the current at B, which is equal to the current at C, which is equal to the current at D.

0.83 mA

A battery is rated that it provides 5 mW of power at 6 V when fully charged. How much current can it deliver? 0.91 mA 1.2 kA 7.2 kA 0.83 mA

0.5 degrees

A bichromatic source produces light having wavelengths in vacuum of 450 nm and 650 nm. The indices of refraction are 1.440 and 1.420, respectively. In the situation above, a ray of the bichromatic light, in air, is incident upon the oil at an angle of incidence of 50.0°. The angle of dispersion between the two refracted rays in the oil is closest to: 0.9° 0.5° 1.3° 0.7° 1.1°

There is an induced current in the wire ring, directed in clockwise orientation

A circular wire ring is situated above a long straight wire, as shown in the figure. The straight wire has a current flowing to the right, and the current is increasing in time at a constant rate. Which statement is true?

90 J

A dipole with ±6 μC charges is positioned so that the positive charge is 1.0 mm to the right of the origin and the negative charge is at the origin. How much work does it take to bring a 10 μC charge from infinity to a position x = 3.0 mm, y = 0.0 mm? A. 200 J B. 75 J C. 90 J D. 450 J

0.901

A glass plate whose index of refraction is 1.57 is immersed in a liquid. The surface of the glass is inclined at an angle of 35° with the vertical. A horizontal ray in the glass is incident on the interface. When the liquid is a certain alcohol, the incident ray arrives at the interface at the critical angle. The index of refraction of the alcohol is closest to: 0.921 0.861 0.901 0.841 0.881

increases

A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the potential energy of the electron: increases. decreases. remains the same. depends on the zero point of the potential.

-5.4x10^−17 N

A long straight wire on the z-axis carries a current I1 = 7 A in the positive direction. A circular loop in the x-y plane, of radius 10 cm, carries a I2 = 9 A current, as shown. Point P, at the center of the loop, is 25 cm from the z-axis. In the figure, an electron is projected from P with a velocity of 6×106m/s in the negative x-direction. The y-component of the force on the electron is closest to: -2.7×10^−17 N zero +2.7×10^−17 N -5.4×10^−17 N +5.4×10^−17 N

upward

A negatively charged particle is moving to the right, directly above a wire having a current flowing to the right, as shown in the figure. In which direction is the magnetic force exerted on the particle? out of the page into the page downward upward The magnetic force is zero since the velocity is parallel to the current.

is repelled by the sphere

A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. After the rod is separated, the rod feels no force due to the sphere. is repelled by the sphere. is attracted to the sphere.

4/5 R

A proton is projected toward a fixed nucleus of charge +Ze with velocity vo. Initially the two particles are very far apart. When the proton is a distance R from the nucleus its velocity has decreased to 1/2vo. How far from the nucleus will the proton be when its velocity has dropped to 1/4vo? 4/5 R 1/2 R 1/16 R 1/4 R None of these.

2300 V

A proton with a speed of 2 x 105 m/s falls through a potential difference V and thereby increases its speed to 7 x 105 m/s. Through what potential difference did the proton fall? 2800 V 210 V 2600 V 2300 V 100 V

1x10^-6 Pa

A radiometer has two square vanes (1 cm by 1 cm), attached to a light horizontal cross arm, and pivoted about a vertical axis through the center. The center of each vane is 6 cm from the axis. One vane is silvered and it reflects all radiant energy incident upon it. The other vane is blackened and it absorbs all incident radiant energy. Radiant energy, which has an intensity of 300 W/m2 is incident normally upon the vanes. In the figure, the radiation pressure on the blackened vane is closest to: 1 × 10^-8 Pa 1 × 10^-6 Pa 1 × 10^-7 Pa 1 × 10^-10 Pa 1 × 10^-9 Pa

39 degrees

A ray in glass arrives at the glass-water interface at an angle of 48° with the normal. The refracted ray, in water, makes a θ = 64° angle with the normal. The index of refraction of water is 1.33. In the figure, the angle of incidence of a different ray in the glass is 31°. The angle of refraction in the water is closest to: 37° 39° 43° 41° 35°

0.69 J

A series ac circuit is shown. The inductor has a reactance of 70 ohms and an inductance of 190 mH. A 60 ohm resistor and a capacitor whose reactance is 110 ohms are also in the circuit. The rms current in the circuit is 1.9 A. In the figure, the peak magnetic energy in the inductor is closest to: 1.0 J 0.34 J 1.4 J 1.7 J 0.69 J

3T

A solenoid of length 18 cm consists of a wire wrapped tightly around a wooden core. The magnetic field strength is 4 T inside the solenoid. If the solenoid is stretched to 24 cm by applying a force to it, what does the magnetic field become? 4 T 38 T 5.3 T 3 T

0.06484 m

A solenoid with 2000 turns is 80 cm long. If its self-inductance is 83 mH, what is its radius? (The value of μo is 4π × 10-7 N/A2.) 0.00509 m 73 m 0.06484 m 456 m

3000 V

A sphere with radius 2.0 mm carries a 2 μC charge. What is the potential difference, VB - VA , between point B 3 m from the center of the sphere and point A 6 m from the center of the sphere? (The value of k is 9.0 × 109 N∙m2/C2.) A. -1.5 V B. 330 V C. -3000 V D. 3000 V

2.2x10^-10 J/m3

A uniform electric field has the strength of 7 N/C. What is the electric energy density of the field? (The value of εo is 8.85 × 10-12 C2/N ∙ m2.) 5.5 × 10^12 J/m3 2.2 × 10^-10 J/m3 2.8 × 10^12 J/m3 3.1 × 10^-11 J/m3

4d

A very long straight current-carrying wire produces a magnetic field of 20 mT at a distance d from the wire. To measure a field of 5 mT due to this wire, you would have to go to a distance of 4d d2√ 2d 8d 16d

from b to a

In the figure, two parallel wires carry a current I in opposite directions. A rectangular loop is midway between the wires. The current I is decreasing. The induced current through the resistor R is: zero from a to b from b to a

2110

An 55 mH solenoid inductor is wound on a form 0.80 m in length and 0.10 m in diameter. A coil is tightly wound around the solenoid at its center. The coil resistance is 4.2 ohms. The mutual inductance of the coil and solenoid is 16 μH. At a given instant, the current in the solenoid is 520 mA, and is decreasing at the rate of 2.5 A/s. The number of turns in the winding of the solenoid is closest to: A. 2030 B. 2270 C. 2190 D. 2110 E. 2360

1.2x10^-3 W/m^2

An 800 kHz radio signal is detected at a point 7.8 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 940 mV/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The intensity of the radio signal at that point is closest to: 1.7×10^-3 W/m^2 8.3×10^-4 W/m^2 1.2×10^-3 W/m^2 2.3×10^−3 W/m^2 5.9×10^−4 W/m^2

-5.8 A/s

An R-L circuit is shown, with a R = 18 ohm resistor and an ideal L = 37 H inductor, that has zero resistance. At time t = 0 s, there is a 12A current in the circuit. In the figurea, at time t = 0 s, the rate of change of the current is closest to: -20 A/s -15 A/s -11 A/s -5.8 A/s -25 A/s

72

An ac source whose rms voltage is 80 V is in series with a 100 ohm resistor and a capacitor whose reactance is 200 ohms at the frequency of the source. In the figure, the rms voltage across the capacitor is closest to: A. 72 V B. 66 V C. 70 V D. 68 V E. 74 V

1.33 kW/m2

An electromagnetic wave has a peak electric field of 1 kV/m. What is the peak intensity of the wave? 1.59 kW/m2 1.33 kW/m2 0.996 kW/m2 1.06 kW/m2

110 T

An electron in a magnetic field has a cyclotron frequency of 3 x 1012 Hz. What is the magnetic field strength? (The mass of an electron is 9.1 x 10-31 kg, and the charge of an electron is 1.6 x 10-19 C.) 12 T 110 T 8.4×10^−2 T 9.3×10^−3 T

7.2x10^-3 N/C

An object with a 5 μC charge is accelerating at 6×10−3 m/s2 due to an electric field. If the object has a mass of 6 mg, what is the magnitude of the electric field? -7.2×10−3 N/C -7.2 N/C 7.2 N/C 7.2×10−3 N/C

497 V

Each plate of a parallel-plate air capacitor has an area of 0.0020 m2, and the separation of the plates is 0.070 mm. An electric field of 7.1 × 106 V/m is present between the plates. The potential difference across the capacitor is closest to: Each plate of a parallel-plate air capacitor has an area of 0.0020 m2, and the separation of the plates is 0.070 mm. An electric field of 7.1 × 106 V/m is present between the plates. The potential difference across the capacitor is closest to: 994 V 331 V 663 V 828 V 497 V

70

Each plate of a parallel-plate air capacitor has an area of 0.0060 m2, and the separation of the plates is 0.040 mm. An electric field of 7.9 × 106 V/m is present between the plates. The surface charge density on the plates, in μC/m2, is closest to: 180 35 70 110 150

B,A,C

Identical light bulbs are attached to identical batteries, as shown in the figure. The ranking (from lowest to highest) of the total power emitted from the light bulb(s) is B, A, C A, C, B C, B, A C, A, B A, B, C

You will experience a magnetic force opposing your action

If you hold a sheet of copper in a strong permanent magnet, with the plane of the sheet perpendicular to the magnetic field, and quickly jerk it out: you will experience a magnetic force assisting your action. any force you feel will be due mainly to iron impurities in the copper, since copper itself is not magnetic. you will feel no magnetic force. you will experience a magnetic force opposing your action. None of these are true.

0.27 A

In the circuit shown in the figure, E1=9V, E2=8V, R1=60Ω, R2=30Ω. What current does the ammeter read? 0.27 A 3.3×10^−2 A 0.71 A 1.05 A

0.31

In the figure, a coil of 8 turns is wound on a square frame, 25 cm by 25 cm. The resistance of the coil is 9.5 ohms. The coil is initially in a horizontal plane and a uniform vertical magnetic field B is present. Two views of the initial orientation of the coil are given in figures (a) and (b). Points P and Q are initially of the left and right sides of the frame, respectively. The coil is flopped over about axis O-O', through 180 degrees, to the final horizontal orientation, shown in figure (c). The time interval, during which the coil is flipped over, is 0.50 s. The average induced current in the coil during the 0.50 s time interval is 66 ma. The magnitude of the magnetic field which is present is closest to: 1.3 T 0.63 T 0.31 T 2.5 T 5.0 T

Rotate the coil around the z-axis

In the figure, a coil of wire is placed on the axis of a solenoid carrying a DC current. Which of the following will NOT result in an EMF being induced in the coil? A. Rotate the coil about the x-axis. B. Change the current in the solenoid. C. Rotate the coil about the y-axis. D. Move the coil toward point P. E. Rotate the coil about the z-axis.

Zero

In the figure, a long bar slides on two contact points and is in motion with velocity ν. A steady, uniform, magnetic field B is present. The induced current through the resistor R is: from a to b from b to a zero

7.64 degrees

In the figure, a small spherical insulator of mass 9.00 × 10-2 kg and charge +0.46 μC is hung by a thin wire of negligible mass. A charge of -0.73 μC is held 0.16 m away from the sphere and directly to the right of it, so the wire makes an angle θ with the vertical (see drawing). What is the angle θ? 7.64° 13.9° 9.11° 12.3° 10.7°

from b to a

In the figure, a straight wire carries a current I. The wire passes through the center of a toroidal coil. The current is quickly reduced to zero. The induced current through the resistor R is: from a to b zero from b to a

Zero

In the figure, a straight wire carries a steady current I. A bar is in contact with a pair of circular rails, and rotates about the straight wire. The induced current through the resistor R is: A. Zero B. From a to b C. From b to a

+18 V

In the figure, the emf ε is closest to: +18 V -18 V -3 V -10 V +3 V

563 W/m2

In the figure, the orientation of the transmission axis for each of three polarizing sheets is labeled relative to the vertical direction. A beam of light, polarized in the vertical direction, is incident on the first polarized with an intensity of 1000 W/m2. What is the intensity of the beam after it has passed through the three polarizing sheets when θ1 = 30°, θ2 = 30°, and θ3 = 60°? 316 W/m2 563 W/m2 141 W/m2 188 W/m2 433 W/m2

I1 decreases, I2 increases

In the figure, the resistor R has a variable resistance. As R is decreased I1 increases, I2 decreases. I1 decreases, I2 increases. I1 decreases, I2 decreases. I1 increases, I2 increases. I1 remains unchanged, I2 increases.

0.562 So

Light of intensity So and polarized horizontally passes through three polarizes. The first and third are horizontal, but the second is oriented 0.5236 rad to the horizontal. In terms of So , what is the intensity of the light that passes through the set of polarizers? 0.188 So 0.562 So 0.75 So 0.375 So

8.12 × 10^13

Suppose a van de Graaff generator builds a negative static charge, and a grounded conductor is placed near enough to it so that a 13 μC of negative charge arcs to the conductor. Calculate the number of electrons that are transferred. 2.08 × 10^-18 81.3 13 8.12 × 10^13

690

The 60 Hz ac source of a series circuit has a voltage amplitude of 120 V. The capacitive and inductive reactances are 770 Ω and 260 Ω, respectively. The resistance is 410 Ω. In the figure, the inductance, in mH, is closest to: 4300 3300 2600 1600 690

None of these

The capacitance of a capacitor depends on The capacitance of a capacitor depends on the charge on it. the potential difference across it. the energy stored in it. More than one of these. None of these.

72

The capacitive network shown is assembled with initially uncharged capacitors. A potential difference, Vab = +100 V, is applied across the network. The switch S in the network is kept open throughout. In the figure, the total energy stored in the seven capacitors, in mJ, is closest to: A. 48 B. 96 C. 120 D. 72 E. 144

9.1x10^−5 N

The charge at the bottom of the figure is Q = +8 nC. What is the magnitude of the force F→ on the charge Q? 1.1×10^−4 N 5.8×10^−5 N 7.4×10^−5 N 9.1×10^−5 N

Double the charge to 2Q

The electric field at point P due to a point charge Q a distance R away has magnitude E. In order to double the magnitude of the field at P, you could double the distance to 2R. reduce the distance to R/4. double the charge to 2Q. double the charge to 2Q and at the same time reduce the distance to R/2. reduce the distance to R/2.

29 W

The emf and the internal resistance of a battery are as shown. In the figure, a 3.0 ohm cable is connected across the battery. The rate at which chemical energy in the battery is depleted is closest to: 24 W 29 W 34 W 27 W 32 W

5.00x10^-8 T

The energy flow per unit time per unit area (S) of an electromagnetic wave has an average value of 298 mW/m2. The maximum value of the magnetic field in the wave is closest to: 3.53×10^−8 T 2.50×10^−8 T 5.00×10^−8 T 9.99×10^−8 T 6.91×10^−8 T

25 degrees

The following are positioned in sequence: A source of a beam of natural light of intensity I0; three ideal polarizers A, B, and C; and an observer. Polarizer axis angles are measured clockwise from the vertical, from the perspective of the observer. The axis angle of polarizer A is set at zero degrees (vertical), and the axis angle of polarizer C is set at 50 degrees. In the situation above, polarizer B is set so that the beam intensity at the observer is a maximum. The axis angle of polarizer B is: 25° 0° 75° 100° 50°

5.375x10^18

The resistivity of gold is 2.44×10^-8Ω⋅m at a temperature of 20°C. A gold wire, 1.7 mm in diameter and 41 cm long, carries a current of 860 mA . The number of electrons per second passing a given cross section of the wire, is closest to: 1.9227×10^15 1.339226×10^23 5.375×10^19 5.375×10^18 6.25×10^15

each conductor must be at the same potential

Two conductors are joined by a long copper wire. Thus: no free charge can be present on either conductor. each conductor carries the same free charge. the electric field at the surface of each conductor is the same. each conductor must be at the same potential. the potential on the wire is the average of the potential of each conductor.

3.7x10^-25 N

Two electrons are passing 25 mm apart. What is the electric repulsive force that they exert on each other? (The value of k is 9.0 × 109 N∙m2/C2.) 1.4 × 10^10 N 3.7 × 10^-27 N 1.4 N 3.7 × 10^-25 N

15

Two small insulating spheres are attached to silk threads. The spheres have equal masses of 40 g and have electric charges of q1 = +2.0 μC and q2 = -2.0 μC. The spheres are brought into the initial positions shown in Figure (a), with a vertical separation of 15 cm between them. In the figure, the upper thread is slowly pulled upward, while point B is kept fixed. When point A has been raised through a height h, the lower sphere suddenly falls, as shown in Figure (b). The height h, is closest to: A. 9 B. 11 C. 13 D. 15 E. 17

sphere #1 carries positive charge and sphere #2 carries negative charge

Two uncharged metal spheres, #1 and #2, are mounted on insulating support rods. A third metal sphere, carrying a positive charge, is then placed near #2. Now a copper wire is momentarily connected between #1 and #2 and then removed. Finally, sphere #3 is removed. In this final state sphere #1 carries positive charge and #2 carries negative charge. sphere #1 carries negative charge and #2 carries positive charge. spheres #1 and #2 both carry positive charge. spheres #1 and #2 both carry negative charge. spheres #1 and #2 are still uncharged.

6x10^-2 A

What is the current through resistor R1 in the circuit in the figure? R1=50Ω, R2=75Ω, R3=100Ω, E1=4V, E1=7V. 0.22 A 6×10^-2 A 4.9×10^-2 A 1.3×10^-2 A

0.21 m

What is the radius of a tightly wound solenoid of circular cross-section that has 230 turns if a change in its internal magnetic field of 3.4 T/s causes a 6.5 A current to flow? The resistance of the circuit that contains the solenoid is 16 Ω. The only emf source for the circuit is the induced emf 0.21 m 0.52 m 0.032 m 0.013 m

its velocity and wavelength change, but its frequency does not change

When light travels from air into water, its velocity, wavelength and frequency all change. its velocity and wavelength change, but its frequency does not change. its frequency changes, but its velocity and wavelength do not change. its wavelength changes, but its velocity and frequency do not change. its velocity changes, but its frequency and wavelength do not change.

All of the above statements are true

While a magnet is moved toward the end of a solenoid (as shown in the figure), a voltage difference is induced between the two ends of the solenoid wire. The voltage difference would be larger if: the speed of the magnet were increased. The bar magnet produced a stronger magnetic field. the solenoid contained more loops (while having the same length). All of the above statements are true. Only two of the above statements are true.

negative and positive

X and Y are two uncharged metal spheres on insulating stands, and are in contact with each other. A positively charged rod R is brought close to X as shown in the figure. What are the final charge states of X and Y, respectively? positive and neutral neutral and positive negative and positive neutral and neutral