PHYSICS 102
The voltage across the input terminals of a transformer is 120 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer delivers is: A) 60 V. B) 30 V. C) 120 V. D) 240 V. E) none of the above.
A) 60 V.
Power is defined as the energy expended per unit of time. When translated to electrical terms, power is equal to: A) current multiplied by voltage. B) current multiplied by resistance. C) current divided by time. D) voltage divided by time. E) voltage divided by resistance.
A) current multiplied by voltage. P = IV
A 60-vibration-per-second wave travels 30 meters in 1 second. Its frequency is: A) 30 Hz and it travels at 60 m/s. B) 1800 Hz and it travels at 2 m/s. C) 60 Hz and it travels at 30 m/s. D) none of the above.
C) 60 Hz and it travels at 30 m/s.
A proton moving in a region of a space does not experience any acceleration in the direction of motion. Which of the following statements is correct with respect to this situation? A) Both electric and magnetic fields must be zero in that region. B) The magnetic field must be zero but not the electric field in that region. C) The electric field must be zero but not the magnetic field in that region. D) The electric and magnetic fields must be parallel to each other in that region. E) The electric and magnetic fields must be perpendicular to each other in that region.
C) The electric field must be zero but not the magnetic field in that region.
Two beams of coherent light travel different paths arriving at point P. If the maximum constructive interference is to occur at point P, what should be the phase difference between the two waves? A) The phase difference between the two waves is π/2. B) The phase difference between the two waves is 5π/2. C) The phase difference between the two waves is 2π. D) The phase difference between the two waves is π/4. E) The phase difference between the two waves is π.
C) The phase difference between the two waves is 2π.
When waves from a pair of closely-spaced slits arrive in phase at a screen: A) a dark fringe is produced. B) both bright and dark fringes are produced. C) a bright fringe is produced. D) none of the these
C) a bright fringe is produced
An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, what is the direction of the magnetic field in this region? A) along the +y-axis B) along the -y-axis C) along the -z-axis D) along the -x-axis E) along the +z-axis
C) along the -z-axis
An ampere is a unit of electric: A) resistance. B) voltage. C) current.
C) current.
Two charges Q1 = -3 uC and Q2 = +3 uC are located on the y-axis at y1 = -5 cm and y2 = +5 cm respectively. A third charge Q3 = +24 uC is added on the y-axis so that the electric field at the origin is equal to zero. What is the position of Q3?
k|Q3|/(y3)^2 = k|Q1 + Q2|/(y)^2 |Q3|/(y3)^2 = |Q1 + Q2|/(y)^2 24E-6/(y3)^2 = 6E-7/25 (y3)^2 = 2.4E-5/2.4E-7 = 100 y3 = +10 or -10 y3 is -10 cm because the charge of Q3 has to be nullified by the charge of Q1.
What is the wavelength of an earthquake that shakes you with a frequency of 11.0 Hz and gets to another city? What is the wavelength of an earthquake that shakes you with a frequency of 11.0 Hz and gets to another city 86.0 km away in 12.0 s?
λ = v / f
You observe that waves on the surface of a swimming pool propagate at 0.750 m/s. You splash the water at one end of the pool and observe the wave go to the opposite end, reflect, and return in 27.5 s. How many meters away is the other end of the pool?
2L = v X t
Camera flashes charge a capacitor to high voltage by switching the current through an inductor on and off rapidly. In what time must the 0.100 A current through a 2.00 mH inductor be switched on or off to induce a 500 V emf?
Ii = 0.100 A If = 0 A L = 0.002 H Vemf = 500 V t = ? = (L delta I)/emf = ((0.002 H)(0.100 A))/500 V = 0.4 microseconds emf = -L(delta I/delta t) L = self-inductance
What is the resonant frequency (f0) of a 1.50 mH inductor connected to a 400.0 microF capacitor.
L = 0.0015 H C = 4E-4 f0 = 1/2π(sq(LC)) = 205.48 Hz
An RLC series circuit has a 40.0 ohms resistor, a 3.00 mH inductor, and a 4.00 microF capacitor. Find the circuit's impedance at 60.0 Hz and at 10.0 kHz.
R = 40.0 ohms L = 0.003 H C = 4E-6 F Xl = 1.13 ohms for 60 Hz Xc = 531 ohms for 60 Hz Xl = 188 ohms for 10000 Hz Xc = 3.18 ohms for 10000 Hz
A plug-in transformer supplies 9.00 V to a video game system. (a) How many turns are in its secondary coil if its input voltage is 120 V and the primary coil has 400 turns? (b) What is its input current when its output is 1.30 A?
Vp = 120 V Np = 400 turns Vs = 9 V
The frequency of a microwave signal is 9.76 GHz. What is its wavelength in meters? A) 5.07x10^-2 m B) 2.07x10^-2 m C) 4.07x10^-2 m D) 3.07x10^-2 m E) 1.07x10^-2 m
Wavelength = Speed of Light/Frequency = 3 x 10^8/9.76 x 10^9 = 0.0307 m
A wave traveling on a Slinky®that is stretched to a total length of 2.1 m takes 1.6 s to travel the length of the Slinky and back again. a. What is the propagation speed of the wave, in meters per second? b. A periodic standing wave is created in the same Slinky stretched to the same length. It contains three antinodes and four nodes. What is the frequency of the wave, in hertz?
a. 2d = v x t v = 4.2/1.6 = 2.625 m/s b. 2.1 m / 1.5 of a wavelength = 1.4 m f = v/wavelength = 2.625/1.4 = 1.875 Hz
A single dog barks at a sound intensity level of β = 88 dB. a. Another dog runs up beside the first dog and starts barking at the same sound intensity level. What sound intensity level in dB do you hear from the two dogs barking? b. Now many other dogs run up and start barking at you. Assuming they all bark at the same sound intensity level, what will the sound intensity level in dB be if there are n = 5 dogs barking at you?
a. 88 + 3 = 91 b. 88 + 7 = 95
In the two-slit experiment, monochromatic light of wavelength 600 nm passes through a pair of slits separated by 2.20 x 10^4 nm. What is the angle corresponding to the first bright fringe?
d = 600/2.20 x 10^4 = .0273 = 1.56 degrees
What is the characteristic time constant for a 17.5 mH inductor in series with a 300 ohms resistor?
tc = L/R L = 0.0175 H R = 300 ohms
A 60-Watt light bulb connected to a 120-Volts source draws a electric current of: A) 2.0 A. B) more than 4 A. C) 0.25 A. D) 4.0 A. E) 0.5 A.
E) 0.5 A. P = VI I = P/V = 60/120 = 0.5 A
A 10-A current flows through a wire for 2.0 min (e = 1.60E-19 C) (a) How much charge has passed through this wire? (b) How many electrons have passed any point in the wire?
(a) Q = I x t Q = 10 A x 120 s = 1200 C (b) = Q/e 1200 C/1.60E-19 = 7.5E21 electrons
Suppose an oncoming ambulance moving at 135 km/h emits a steady 810-Hz sound from its siren. a. What frequency, in Hz, is received by a person watching the oncoming ambulance? The speed of sound on this day is 345 m/s. b. What frequency, in Hz, does she observe after the ambulance has passed?
135 km/h 37.5 m/s a. fobs = fs(vw/vw - vs) fobs = (810)(345/345 - 37.5) fobs = (810)(1.122) = 908.8 b. fobs = fs(vw/vw + vs) fobs = (810)(345/345 + 37.5) fobs = (810)(0.902) = 730.6
Three point charges are placed on the x-axis. A charge of +2.0 μC is placed at the origin, -2.0 μC to the right at x = 50 cm, and +4.0 μC at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin? A) 0.072 N, toward the right B) 0.052 N, toward the left C) 0.072 N, toward the left D) 0.052 N, toward the right
A) 0.072 N, toward the right F = k(q1q2)/r^2 - k(q1q3)/r^2 F = k(2E-6x2E-6)/0.5^2 - k(4E-6x2E-6)/1^2 k = 8.99e9 F = 0.07192 N
A particle with a charge of +4.0 µC has a mass of 5.0 g. What magnitude electric field directed upward will exactly balance the weight of the particle? A) 1.2 x 10^4 N/C B) 8.2 x 10^4 N/C C) 4.4 x 10^4 N/C D) 4.1 x 10^4 N/C E) 5.1 x 10^4 N/C
A) 1.2 x 10^4 N/C E = F/q E = (0.005 kg)(9.81)/(4.0 x 10^-6 C) E = 1.2 x 10^4 N/C
A solenoid of length 5.0 cm has a cross sectional area of 1.0 cm^2 and has 300 uniformly spaced turns. The solenoid is wrapped in 180 turns of insulated wire resulting in a mutual inductance of A) 1.4 × 10-4 H. B) 110 H. C) 1.1 H. D) 11 H. E) 1.4 × 10-2 H.
A) 1.4 × 10-4 H. ℓ = 0.05 m A = 0.01 m^2 N = 300 turns µ0 = 4πE-7 L = µ0 N^2 A/ℓ
A series LRC circuit has a 100-Ω resistor, a 0.100-μF capacitor and a 2.00-mH inductor connected across a 120-V rms ac voltage source operating at (1000/π) Hz. What is the resonant frequency of this circuit? A) 11.3 kHz B) 22.5 kHz C) 35.3 kHz D) 70.7 kHz E) 17.9 kHz
A) 11.3 kHz R = 100 ohms C = 1E-7 F L = 0.002 H Vrms = 120 V f0 = ? = 1/1/2π(sq(LC)) = 11254 Hz
The current in two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is: A) 220 Ω. B) 44 Ω. C) 22 Ω. D) 440 Ω. E) none of the above.
A) 220 Ω. V = IR R = V/I R = (110 V)/(0.25 A) = 440 Ω for two light bulbs 440 Ω / 2 = 220 Ω
An ideal parallel-plate capacitor has a capacitance of C. If the area of the plates is doubled and the distance between the plates is halved, what is the new capacitance? A) 4C B) C/2 C) 2C D) C/4
A) 4C C = A/d
A flat circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are perpendicular. A) 6.3 × 10^-3 T ∙ m^2 B) 3.1 × 10^-3 T ∙ m^2 C) 0 T ∙ m^2 D) 5.5 × 10^-3 T ∙ m^2
A) 6.3 × 10^-3 T ∙ m^2 MF = BA cos θ B = magnetic field = 0.20 T A = Area = πr^2 = 0.0314 m^2
For an electron moving in a direction opposite to the electric field: A) its potential energy decreases and its electric potential increases. B) its potential energy increases and its electric potential decreases. C) its potential energy increases and its electric potential increases. D) its potential energy decreases and its electric potential decreases. E) both its potential energy and it electric potential remain constant.
A) its potential energy decreases and its electric potential increases.
An LR circuit includes a resistor of resistance R, an inductor of inductance L and a battery of emf E = 10 V. At time t = 0 the current in the circuit is I = 0. At time t = 6.1 ms the current is I = 0.66 A. What are the values of L and R? A) not enough information given B) L = 10 mH, R = 100 Ω C) L = 50 mH, R = 150 Ω D) L = 2 mH, R = 10 Ω E) L = 15 mH, R = 20 Ω
A) not enough information given
A coil with a self-inductance of 6.0 H is connected to a dc source through a switch. As soon as the switch is closed at t = 0 s, the rate of change of current is 2.0 A/s. What is the emf induced in this coil at t = 0 s? A) 0.33 V B) 12 V C) 0 V D) 6.0 V E) 3.0 V
B) 12 V L = 6.0 H
Four equal point charges of magnitude 6.00 μC are placed at the corners of a square 2.00 m on each side, as shown in Figure 20-4. What is the electric potential of these charges at the center of this square? A) 61.0 kV B) 153 kV C) 38.2 kV D) 306 kV E) 76.4 kV
B) 153 kV V = kq/r r = sqrt(2) m k = 9.0 x 10^9 q = 6.0 x 10^-6 C
The magnetic field at a point P, a certain distance from a long wire carrying a current of 2.0 A, is 1.2 × 10^-6 T. How far is P from the center of the wire? A) 11 cm B) 33 cm C) 55 cm D) 44 cm E) 22 cm
B) 33 cm R = μ₀ I/(2 π B ) = (4π * 10^-7 T m/A* 2.0 A)/(2 π 1.2 10^-6 T ) = 33 cm
A certain transformer doubles input voltage. If the primary coil draws 10 A of current, then the current in the secondary coil is: A) 2 A. B) 5 A. C) 25 A. D) 10 A. E) none of the above.
B) 5 A.
A current-carrying coil of wire is: A) a magplane in the making. B) an electromagnet. C) a superconductor. D) a superconducting magnet.
B) an electromagnet.
The type of lens that brings parallel light rays together is a: A) combination of converging-diverging lens. B) converging lens. D) diverging lens.
B) converging lens
It is said that electric charge is quantized, which means that the charge on an object: A) may occur in an infinite variety of quantities. B) is a whole-number multiple of the charge of one electron. C) can be neither created nor destroyed. D) is sometimes positive. E) will interact with neighboring electric charges.
B) is a whole number multiple of the charge of one electron.
Two charged particles held a certain distance apart are released. As they move, the force on each particle increases. Therefore, their charges have: A) the same mass. B) opposite signs. C) the same size. D) the same sign. E) the same mass density.
B) opposite signs.
At what frequency will an 160.0 mF capacitor have a reactance of 0.250 ohms?
C = 0.160 F Xc = 0.250 ohms f = 1/2πXcC Xc = 1/2πfC
A styrofoam ball of mass 0.120 g is placed in an electric field of 6000 N/C pointing downward. What charge must be placed on the ball for it to be suspended? A) -57.2 nC B) -16.0 nC C) -196 nC D) -18.0 nC E) -125 nC
C) -196 nC E = 6000 N/C F = (0.00012 kg)(9.8m/s^2) = 0.001176 N q = F/E = 0.001176/6000 = -1.96 x 10^-7 Negative because the electric field was pointing downward
A rectangular loop of wire, with dimensions as shown in Figure 22-8, carrying a 2-A current is placed in a magnetic field of 0.8 T. The loop rotates in the magnetic field and at one point makes a 30° angle with the magnetic field. What is the magnitude of the torque acting on the wire? Area of the loop is 0.6 m^2. A) 0.3 Nm B) 0.6 Nm C) 0.5 Nm D) 0.4 Nm E) 0.7 Nm
C) 0.5 Nm
What must be the diameter of a cylindrical 120-m long metal wire if its resistance is to be 6.0 Ω? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m. A) 0.0325 mm B) 0.65 cm C) 0.65 mm D) 0.325 mm E) 0.065 mm
C) 0.65 mm Resistance of a wire in Ω R = ρL/A ρ is resistivity of the material in Ω-m L is length in meters A is cross-sectional area in m² A = πr², r is radius of wire in m 6 = (120)(1.68e-8) / A solve for A, plug into: A = πr² solve for r. Diameter is 2x that.
The magnetic flux through a coil changes steadily from 4.0 × 10^-5 T ∙ m^2 to 5.0 × 10-5 T ∙ m^2 in 0.10 s. What emf is induced in this coil? A) 4.0 × 10^-4 V B) 5.0 × 10^-4 V C) 1.0 × 10^-4 V D) None of the given answers are correct.
C) 1.0 × 10^-4 V MF = 1.0 x 10^-5 T ∙ m^2 t = 0.10 s N = 1 turn emf = N(MF/t)
The approximate range of human hearing is: A) 40 hertz to 40,000 hertz. B) 10 hertz to 10,000 hertz. C) 20 hertz to 20,000 hertz. D) none of the above.
C) 20 hertz to 20,000 hertz.
A 6.0-Ω and a 12-Ω resistor are connected in parallel across an ideal 36-V battery. What power is dissipated by the 6.0-Ω resistor? A) 490 W B) 24 W C) 216 W D) 48 W
C) 216 W V all equal in parallels I = V/R = 36/6 = 6 A P = VI = (36)(6) = 216 W
A charged particle is observed traveling in a circular path of radius R in a uniform magnetic field. If the particle were traveling twice as fast, the radius of the circular path would be: A) 4R. B) R/2. C) 2R. D) 8R. E) R/4
C) 2R R = (mv)/(Bq)
The electrical force on a 2-C charge is 60 N. The electric field where the charge is located is: A) 120 N/C. B) 240 N/C. C) 30 N/C. D) 60 N/C. E) 20 N/C.
C) 30 N/C. E = F/Q E = (60 N)/(2 C) = 30 N/C
In a certain electroplating process gold is deposited by using a current of 14.0 A for 19 minutes. A gold ion, Au+, has a mass of approximately 3.3 × 10-22 g. How many grams of gold are deposited by this process? A) 16 g B) 97 g C) 33 g D) 22 g E) 28 g
C) 33 g According to Faraday's law: m = MQ/zF where m = deposited mass M = molar mass = mass x Avogadro's number = 3.3x10^-22 x 6.02x10^23 = 198.7 g Q = total charge = current x time = 14 x 19 x 60 = 15960 C z = valence = 1 F = Faraday's constant = 96485 C/mol Then m = 198.7x 15960 / 96485 = 32.87 g
An object 4.0 cm in height is placed 8.0 cm in front of a concave mirror with a focal length of 10.0 cm. What is the position of its image in relation to the mirror and what are its characteristics? A) 18.0 cm on the same side of mirror, virtual, 2.25 times bigger B) 10.0 cm on the other side of mirror, virtual, 10.0 times bigger C) 40.0 cm on the other side of mirror, virtual, 5.0 times bigger D) 40.0 cm on the other side of mirror, real, 6.0 times bigger E) 10.0 cm on the same side of mirror, real, 6.0 times bigger
C) 40.0 cm on the other side of mirror, virtual, 5.0 times bigger di = 1/(1/f - 1/do) = 1/(1/10 - 1/8) = -40 cm (so it's virtual due to being between the mirror and object) m = -di/do = 40/8 = 5 (so it's 5 times bigger)
A bar magnet is pushed through a coil of wire of cross-sectional area 0.020 m^2 as shown in the figure. The coil has seven turns, and the rate of change of the strength of the magnetic field in it due to the motion of the bar magnet is 0.040 T/s. What is the magnitude of the induced emf in that coil of wire? A) 5.6 × 10^-2 V B) 5.6 × 10^-4 V C) 5.6 × 10^-3 V D) 5.6 × 10^-5 V E) 5.6 × 10^-1 V
C) 5.6 × 10^-3 V N = 7 turns A = 0.020 m^2 B/t = 0.040 T/s emf = NA (dB/dt)
Light is reflected when: A) electron clouds of atoms are energized. B) electromagnetic waves emanate from matter. C) incident light is returned into the medium from which it came. D) atomic nuclei are made to vibrate.
C) incident light is returned into the medium from which it came.
The highest frequency of visible light is: A) blue. B) red. C) violet. D) green. E) yellow.
C) violet.
Homework 10
Chapter 23
A student wishes to build a telescope. She has available an eyepiece of focal length -5.0 cm. What focal length objective is needed to obtain a magnification of 10x? A) - 50 cm B) + 16.7 cm C) - 41.3 cm D) + 50 cm E) + 41.3 cm
D) + 50 cm m = -fo/fe = -fo/-5 10 x -5 = -fo = -(50) fo = 50
A capacitor of capacitance C = 5 μF and initial charge Q = 30 μC is connected to an inductor of inductance L = 20 mH. What is the electric current in the circuit when the energy stored in the capacitor is 25% of its maximum value? A) 0.001 A B) 0.01 A C) .02 A D) 0.08 A E) 0.04 A
D) 0.08 A C = 5E-6 F Q = 3E-5 C L = 0.02 H V = Q/C = IR I = V/L
A 25.0-mH inductor is connected in series to a 20.0-Ω resistor through a 15.0-V dc power supply and a switch. If the switch is closed at t = 0 s, what is the time constant of this circuit? A) 0.800 × 10-2 s B) 0.500 s C) 0.800 × 10-3 s D) 1.25 × 10-3 s E) 12.5 × 10-2 s
D) 1.25 × 10-3 s L = 0.025 H R = 20 ohms V = 15.0 V tc =
At what rate would the current in a 100-mH inductor have to change to induce an emf of 1000 V? A) 1 A/s B) 10 A/s C) 100 A/s D) 10,000 A/s E) 1000 A/s
D) 10,000 A/s M = 0.1 H emf = 1000 V I/t = emf/M = 1000/0.1 = 10000 A/s
Two charges (like protons) that are separated by one meter exert 1-N forces on each other. If the charges are pushed together so the separation is 25 centimeters, the force on each charge will be: A) 1 N. B) 2 N. C) 8 N. D) 16 N. E) 4 N.
D) 16 N. F = k(q^2)/r
A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T, as shown in the figure. The length of the loop L is 0.16 m and its width w is 0.040 m. What is the magnetic flux through the loop when the plane of the loop makes an angle of 60° with the magnetic field? A) 0 T ∙ m^2 B) 1.3 × 10-3 T ∙ m^2 C) 2.6 × 10-3 T ∙ m^2 D) 2.2 × 10-3 T ∙ m^2 E) 0.80 T ∙ m^2
D) 2.2 × 10-3 T ∙ m^2 B = 0.40 T L = 0.16 m w = 0.040 m A = Lw = (0.16)(0.040) = .0064 m^2 MF = BA cos θ
A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T, as shown in the figure. The length of the loop L is 0.16 m and its width w is 0.040 m. What is the magnetic flux through the loop when the plane of the loop is perpendicular to the magnetic field? A) 2.6 × 10^3 T ∙ m^2 B) 0.80 T ∙ m^2 C) 0 T ∙ m^2 D) 2.6 × 10^-3 T ∙ m^2 E) 13 × 10^-3 T ∙ m^2
D) 2.6 × 10^-3 T ∙ m^2 B = 0.40 T L = 0.16 m w = 0.040 m A = Lw = (0.16)(0.040) = .0064 m^2 MF = BA cos θ
Consider an equilateral triangle of side 20. cm. A charge of +2.0 μC is placed at one vertex and charges of -4.0 μC are placed at the other two vertices. Determine the magnitude and direction of the electric field at the center of the triangle. A) 5.7 x 10^6 V/m B) 1.7 x 10^6 V/m C) 4.05 x 10^6 V/m D) 2.7 x 10^6 V/m
D) 2.7 x 10^6 V/m Distance between charges and origin (r) = .1414 m E = kq/r^2 k = 9.0E9 E = k(2E-6/.1414^2 - 4E-6/.1414^2 - 4E-6/.1414^2) E = |-2700815.64| = 2.7E6 V/m
A 4.0-MΩ resistor is connected in series with a 0.50-μF capacitor. The capacitor is initially uncharged. The RC combination is charged by a 9.0-V battery. What is the change in voltage between t = RC and t = 3RC? A) 11 V B) 5.7 V C) 15 V D) 2.9 V E) 7.6 V
D) 2.9 V Time Constant T = RC = (4)(0.5) = 2 sec V1 = Vo*(1-e^-1) V2 = Vo*(1-e^-3) Delta V = V1V2 = 9(0.9502-0.6321) = 9(0.3181)
Radio waves travel at the speed of light, 300,000 km/s. The wavelength of a radio wave received at 100 megahertz is: A) 0.3 m. B) 30 m. C) 300 m. D) 3.0 m. E) none of the above.
D) 3.0 m. 1 km = 1000 meters; 1 mHz = 1 million Hz λ = v÷f = 300,000 km/s ÷ 100 mHz = 300,000,000 m/s ÷ 100,000,000 Hz = 3.0 m or 0.003 km
An electron moving perpendicular to a magnetic field of 2.2 × 10^-2 T moves in a circle of certain radius. If the electron is moving with a speed of 1.5 × 10^7 m/s, what is the radius of the circle? A) 3.9 × 10^-4 m B) 2.2 × 10^-3 m C) 1.5 × 10^-3 m D) 3.9 × 10^-3 m E) 2.2 × 10^-4 m
D) 3.9 × 10^-3 m Fs = m * v^2/R This force is equal to the magnetic force : Fm = e * B * v Then e * v * B = m * v^2/r SO R = m *v/ B * e The radius of the circle : R = m * v/ B * e ---m = mass v = speed B = magnetic field e = electron's charge R = 9.11 x 10^-31 * 1.5 x 10^7/2.2 x 10^-2 1.6 x 10^-19 = 0.00388 m = 3.9 x 10^-3 m ( B)
An LC circuit with an inductance of 36 mH and a capacitance of 25 mF will oscillate with what frequency? A) 210 Hz B) 1.44 Hz C) 33 Hz D) 5.3 Hz E) 0.03 Hz
D) 5.3 Hz L = 0.036 H C = 0.025 F f = 1/2π(sq(LC)) = 5.31 Hz
How many electrons are necessary to produce 1.0 C of negative charge? (e = 1.60 x 10^-19 C) A) 1.6 x 10^19. B) 6.0 x 10^23. C) 1.6 x 10^9. D) 6.3 x 10^18. E) 6.3 x 10^9.
D) 6.3 x 10^18 1.0 C x (1 e- / 1.60 x 10^-19 C) = 6.3 x 10^18 e-
A 4.0 μF capacitor is connected in series with a 2.0 kΩ resistor across a 20-V DC source and an open switch. If the switch is closed at t = 0 s, what is the charge on the capacitor at t = 9 ms? A) 37% of the minimum charge B) 68% of the minimum charge C) 0 C D) 68% of the maximum charge E) 96% of the maximum charge
D) 68% of the maximum charge
The number of nodes, including the end points, in a standing wave that is three wavelengths long is: A) 6. B) 5. C) 4. D) 7. E) none of the above.
D) 7
As a proton moves in the direction the electric field lines: A) it is moving from low potential to high potential and gaining electric potential energy. B) it is moving from low potential to high potential and losing electric potential energy. C) it is moving from high potential to low potential and gaining electric potential energy. D) it is moving from high potential to low potential and losing electric potential energy. E) both its electric potential and electric potential energy remain constant.
D) It is moving from high potential to low potential and losing electric potential energy.
The voltage across a 10 Ω resistor carrying 5 A is: A) 15 V. B) 20 V. C) 10 V. D) more than 20 V. E) 5 V.
D) more than 20 V. V = IR V = (5 A)(10 Ω) = 50 V
A proton moving eastward with a velocity of 5.0 × 10^3 m/s enters a magnetic field of 0.20 T pointing northward. What is the magnitude and direction of the force that acts on the proton? A) 0 N B) 4.4 × 10^-16 N westwards C) 1.6 × 10^-16 N downwards D) 1.1 × 10^-16 N eastwards E) 1.6 × 10^-16 N upwards
E) 1.6 × 10^-16 N upwards
A 120-V rms voltage at 1000 Hz is applied to a series LRC circuit with an equal value of inductive and capacitive reactance and a 200-Ω resistance. What is the impedance of this circuit? A) 100 Ω B) 0 Ω C) 240 Ω D) 120 Ω E) 200 Ω
E) 200 Ω Vrms = 120 V f = 1000 Hz R = 200 ohms XL = XC Z = square root of R^2 = 200 ohms
The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential (relative to infinity) at a distance of 2 m from the same charge? A) 50 V. B) 600 V. C) 200 V. D) 100 V E) 400 V.
E) 400 V E = V/d E = (200 V)/(d/2)
An electron is accelerated from rest through a potential difference of 3750 V. It enters a region where the magnetic field is 4.0 mT perpendicular to the velocity of the electron. Calculate the radius of the path this electron will follow. A) 4.2 cm B) 2.2 cm C) 1.2 cm D) 3.2 cm E) 5.2 cm
E) 5.2 cm
A +5.0-μC charge is moved from a negative to a positive plate of a parallel plate capacitor. In moving this charge 0.30 mJ of energy is used. What is the potential difference between the plates of this capacitor? A) 23 V B) 0 V C) 81 V D) 55 V E) 60 V
E) 60 V W = -0.3 mJ = -qΔV ΔV = W/-q = -0.3 x 10^-3/-5 x 10^-6 ΔV = 60 V
As shown in the figure, a wire and a 10-Ω resistor are used to form a circuit in the shape of a square with dimensions 20 cm by 20 cm. A uniform but non-steady magnetic field is directed into the plane of the circuit. The magnitude of the magnetic field is steadily decreased from 2.70 T to 0.90 T in a time interval of 96 ms. What is the induced current in the circuit, and what is its direction through the resistor? A) 75 mA, from a to b B) 45 mA, from b to a C) 45 mA, from a to b D) 110 mA, from a to b E) 75 mA, from b to a
E) 75 mA, from b to a dB = 1.8 T dt = 0.096 s A = .04 m^2 R = 10 ohms emf = IR = dMF/dt = (A dB)/dt so I = (A dB)/(R dt)
The inductive reactance of a 20.0-mH inductor at a certain frequency is 120 Ω. What is the frequency in Hz? A) 6000 Hz B) 167 Hz C) 120 Hz D) 478 Hz E) 955 Hz
E) 955 Hz L = 0.02 H XL = 120 ohms = 2πfL f = XL/(2πL) = 120/(2π*0.02) = 955 Hz
Both a transverse wave and a longitudinal wave have: A) amplitude. B) wavelength. C) frequency. D) speed. E) all of the above.
E) All of the above.
Which of these electromagnetic waves have the shortest wavelength? A) infrared waves B) radio waves C) light waves D) ultraviolet waves E) X-rays
E) X-rays
An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected across a battery that maintains a constant potential difference between the plates. If the separation between the plates is now doubled, the magnitude of the charge on the plates will: A) not change. B) double. C) be cut in fourth. D) quadruple. E) be cut in half.
E) be cut in half. C = A/d
How much energy is stored in a L = 0.635 mH inductor when a 25 A flows through it?
Eind = (1/2)LI^2
A copper penny has a mass of 3.0 grams. A total of 4.0 x 10^12 electrons are transferred from one neutral penny to another. If the electrostatic force of attraction between the pennies is equal to the weight of a penny, what is the separation between them?
Electron charge = 1.60 x 10^-19 C q1 = (4.0 x 10^12)(1.60 x 10^-19) = +6.4 x 10^-7 C q2 = -6.4 x 10^-7 C k = 8.99 x 10^9 F = k|q1q2|/r^2 = (.003 kg)(9.8 m/s^2) = 0.0294 N r^2 = k|q1q2|/F = (8.99 x 10^9)(6.4 x 10^-7)^2/0.0294 r^2 = 0.1253 r = 0.35 m = 35 cm
A radio station broadcasts at 80 MHz. How long does it take for this radio signal to travel a distance of 2.0 × 10^7 m through space? (c = 3.0 × 10^8 m/s). A) 6.7x10^-2 s B) 0.15x10^-2 s C) 25 ms D) 15 ms E) 20 ms
Time = Distance/Speed t = d/v = 2.0 × 10^7/3.0 × 10^8 = .067 s
A 8.0 μF capacitor is connected in series with a 6.0 kΩ resistor across a 20-V DC source and a switch. What is the time constant of this RC circuit? A) 18 ms B) 12 ms C) 48 ms D) 40 ms E) 9.0 ms
Time Constant T = RC = (8)(6) = 48 ms
A student attaches a f = 2.5 kHz oscillator to one end of a metal rail of length L= 25 m. The student turns on the oscillator and uses a piezoelectric gauge at the other end to measure that the resulting sound wave takes t = 0.0059 s to travel the length of the rail. a. Input an expression for the period of the waves in the rail, in terms of the given quantities. b. What is the period, in seconds? c. What is the speed of the wave in the rail, in meters per second? d. What is the wavelength of the wave within the rail, in meters?
a. T = 1/f b. T = 1/2500 = 4E-4 s c. 25/0.0059 = 4237.3 m/s d. Wavelength = Tv = (0.0004 x 4237.3) = 1.6949 m
A physicist at a fireworks display times the lag between seeing an explosion and hearing its sound, and finds it to be 0.45 s. a. How far away is the explosion, in meters, if the air temperature is 19.5°C and if you neglect the time taken for light to reach the physicist? b. Calculate the distance, in meters, to the explosion taking the speed of light into account. (Note that this distance is negligibly greater than what you found in part (a).)
a. Vw = (331)(sqrert(T/273.15)) T = 19.5 + 273.15 = 292.65 Vw = (331)(sqrert(292.65/273.15)) Vw = (331)(1.035) = 342.6 m/s L = (342.6)(0.45) = 154.2 m
You are hiking along a trail in a wide, dry canyon where the outdoor temperature is T= 31° C. To determine how far you are away from the canyon wall you yell "Hello" and hear the echo t = 1.8 s later. a. Calculate the speed of sound in the valley in meters per second, assuming the speed at 0° C is 332 m/s. b. How far are you from the canyon wall, in meters? c. If you stood at the same point on a cold morning where the temperature was T2 = -1.5 degrees C, how long would it have taken for you to hear the echo, in seconds?
a. Vw = (331)(sqrert(T/273.15)) T = 31 + 273.15 = 304.15 Vw = (331)(sqrert(304.15/273.15)) Vw = 349 m/s b. 2L = vt 2L = (349)(1.8) = 628.2 L = 314.1 m c. Vw = (331)(sqrert(T/273.15)) T = -1.5 + 273.15 = 271.65 Vw = (331)(sqrert(271.65/273.15)) Vw = 330 m/s 2L = vt 2(314) = (330)t 628/330 = t = 1.9 s
Air temperature in the Sahara Desert can reach 56.0°C (about 134°F). a. What is the speed of sound, in meters per second, in the air at that temperature?
a. Vw = (331)(sqrert(T/273.15)) T = 56 + 273.15 = 329.15 Vw = (331)(sqrert(329.15/273.15)) Vw = 363 m/s
A student standing in a canyon yells "echo", and her voice produces a sound wave of frequency of f = 0.66 kHz. The echo takes t = 2.4 s to return to the student. Assume the speed of sound through the atmosphere at this location is v = 339 m/s. a. What is the wavelength of the sound wave in meters? b. Input an expression for the distance, d, the canyon wall is from the student. c. How many wavelengths are between the student and the wall?
a. Wavelength = v/f = 339/600 = 1.97 m/s b. 2d = vt 2d = (339)(2.4) = 813.6 m d = 406.8 m c. 406.8/.565 = 720 m
The captain of a crab boat on the coast of Alaska notes that in a time period of t = 11 minutes, the boat goes up and down n = 13 times. a. Input an expression for the frequency of the ocean wave, f. b. What is the frequency, in hertz? c. If the crests are d = 100.0 m apart how fast are the waves traveling in meters per second?
a. f = n/t b. f = 13/(11 x 60) = .0197 Hz c. 13 x 100 m = 1300 m; 1300/(11 x 60) = 1.97 m/s
Sound travels at a speed of v = 1560 m/s in water. While underwater a student hears f = 2.5 kHz note in a whale song. a . Input an expression for the wavelength of the sound wave in water λw. b. What is the wavelength in meters?
a. λ = v / f b. λ = 1560/2500 = 0.624 m
A 4.0-cm-tall object is placed 50.0 cm from a diverging lens of focal length 25.0 cm. What is the nature and location of the image? A) A virtual image, 2.0 cm tall, 10 cm other side of the object B) A real image, 4.0 cm tall, 20 cm other side of the object C) A virtual image, 1.3 cm tall, 16.7 cm same side as the object D) A real image, 1.3 cm tall, 16.7 cm same side as the object E) A virtual image, 4.0 cm tall, 20 cm other side of the object
di = 1/(1/f - 1/do) = 1/(1/-25 - 1/50) di = -16.67 cm (so it's virtual and same side as object) m = -di/do = 16.67/50 = + 0.333 hi = (h0)(m) = (4)(0.333) = + 1.3 C) A virtual image, 1.3 cm tall, 16.7 cm same side as the object
In a single-slit diffraction experiment, the width of the slit is 1.90 μm. If a beam of light of wavelength 610 nm forms a diffraction pattern, what is the angle associated with the first minimum above the central bright fringe? A) 9.35° B) 39.9° C) 18.7° D) 11.4° E) 12.2°
m = Order of Minimum D = Width of Slit sin θ = mλ/D sin θ = 1(6.1 x 10^-7)/1.9 x 10^-6 = .3211 rad sin θ = .3211 rad θ = sin^-1 (.3211 rad) = 18.73 degrees
