EP2 Comprehensive Multiple Choice Study Guide
E) 6 C
9 C of charge is placed on a spherical conducting shell. A particle with a charge of −3 C is placed at the center of the cavity. The net charge on the outer surface of the shell is A) -6 C B) -3 C C) Zero D) 3 C E) 6 C
B) -1.6 x 10^-17 J
An electron is transported from a point where the electric potential is 20 V to a point where the potential is 120 V. The change in its potential energy is A) -1.6 x 10^-21 J B) -1.6 x 10^-17 J C) 100 V D) 1.6 x 10^-21 J E) 1.6 x 10^-17 J
B) the work it does on charges
An emf source is defined in terms of A) the force it exerts on charges B) the work it does on charges C) the electric field it generates D) the current it generates E) the charge it emits
D) 4 m away from the charge
An isolated point charged point particle produces an electric field with magnitude E at a point 2 m away from the charge. A point at which the field magnitude is E/4 is: A) 0.5m away from the charge B) 1m away from the charge C) 2m away from the charge D) 4 m away from the charge E) 8m away from the charge
E) 5.6 x 10^4 N/C
An electric field is set up between two parallel plates, each of area 2.0 m2 , by putting 1.0 µC of charge on one plate and −1.0 µC of charge on the other. The plates are separated by 4.0 mm with their centers opposite each other, and the charges are distributed uniformly over the surface of the plates. What is the magnitude of the electric field between the plates at a distance of 1.0 mm from the positive plate, but not near the edges of the plates? A) 4.2 x 10^4 N/C B) 1.4 x 10^4 N/C C) 3.1 x 10^4 N/C D) 0.00 N/C E) 5.6 x 10^4 N/C
B) the work done by the field is negative and the potential energy of the electron increases
An electron is moved from point i to point f, in the direction of a uniform electric field E . During this motion: https://i.imgur.com/fGe7D6Q.png A) the work done by the field is positive, and the potential energy of the electron decreases B) the work done by the field is negative and the potential energy of the electron increases C) the work done by the field is positive and the potential energy of the electron decreases D) the work done by the field is negative and the potential energy of the electron decreases E) the work done by the field is positive and the potential energy of the electron does not change
A) 458
In a transformer, how many turns are necessary in a 110-V primary if the 24-V secondary has 100 turns? A) 458 B) 4 C) 22 D) 110 E) 240
E) none of the above
In amperes law, the symbol ds is A) an infinitesimal piece of the wire that carries current i B) in the direction of B C) perpendicular to B D) a vector whose magnitude is the length of the wire that carries i E) none of the above
C) 30 N/C
Charge is distributed uniformly on the surface of a large flat plate. The electric field 2 cm from the plate is 30 N/C. The electric field 4 cm from the plate is approximately: A) 7.5 N/C B) 15 N/C C) 30 N/C D) 60 N/C E) 120 N/C
E) None of the others
Consider Gausses Law, Which of the following is true A) If Qenc=0 then E=0 everyone on the Gaussian surface B) E must be the electric field due to the enclosed charge C) If a charge is placed outside the surface, then it cannot affect E at any point on the surface D) E is parallel to dA everywhere on the surface E) None of the others
B) 3.0 x 10^8 J
During a lightning discharge, 30 C of charge move through a potential difference of 1.0×10^8 V in 2.0 × 10^−2 s. The energy released by this lightning bolt is A) 1.5 x 10^11 J B) 3.0 x 10^8 J C) 6.0 x 10^7 J D) 3.3 x 10^6 J E) 6.7 x 10^4 J
B) 2.4E-4 Nm
For Motor Madness, one team made a rectangular coil with 8 turns with 3.0 cm length and 1.0 cm width. If 200 mA current is sent through this coil, what would be the magnitude of its magnetic dipole moment? A) 3.0E-4 Nm B) 2.4E-4 Nm C) 6.4E-4 Nm D) 1.5E-3 Nm E) None of the above
A) only the direction of the particle's velocity
For a charged particle, a uniform magnetic field can be used to change A) only the direction of the particle's velocity B) only the magnitude of the particle's velocity C) both the magnitude and direction of the particle's velocity D) neither the magnitude nor the direction of the particle's velocity
B) are planes parallel to the yz plane
For the electric potential V = 1.5x 2 − 2.7x, equipotential surfaces A) are planes containing the x axis B) are planes parallel to the yz plane C) are concentric spheres centered at the origin D) are concentric cylinders with the x axis as the cylinder axis E) cannot be determined from information provided
B) -i
Four equal negative point charges are located at the corners of a square, their positions in the xy-plane being (1,1), (−1,1), (−1,−1), (1,−1). The electric field on the x-axis at (1,0) points in the same direction as A) i B) -i C) j D) -j E) k
C) doesn't affect the current
Grounding a single loop circuit A) increases the current B) decreases the current C) doesn't affect the current D) reduces the current to zero E) shorts out the battery
D) decreasing the plate seperation
The capacitance of a parallel-plate capacitor can be increased by: A) increasing the charge B) decreasing the charge C) increasing the plate separation D) decreasing the plate seperation E) increasing the voltage
A) unit vector that points from q1 to q2
The coloumb force between on charge q2 due to charge q1 is https://i.imgur.com/x1UFu7I.png In this expression r is A) unit vector that points from q1 to q2 B) a unit vector that points from q2 to q1 C) a unit vector from the origin to q1 D) a unit vector from the origin to q2 E) a displacement vector from q1 to q2
C) 0.5 mm/s
The current density in a wire is 4.8 × 10^6 A/m2 . If the density of conduction electrons is 6.0 × 10^28 m^-3 , the drift speed of the electrons is A) 2.0 km/s B) Zero C) 0.5 mm/s D) 5.0 mm/s E) 20 km/s
C) a capacitor
The phasor diagram shown below corresponds to an alternating emf source connected to https://i.imgur.com/sIPw6k3.png A) a resistor B) an inductor C) a capacitor D) a conductor E) none of the others
B) c=ω/k
The relation c = λf is equivalent to A) c=ωk B) c=ω/k C) c= k/ω D) c=1/(ωk) E) None of the others
B) the current in 1 is half that in 2
The resistance of resistor 1 is twice the resistance of resistor 2. The two are connected in parallel and a potential difference is maintained across the combination. Then: A) the current in 1 is twice that in 2 B) the current in 1 is half that in 2 C) the potential difference across 1 is twice that across 2 D) the potential difference across 1 is half that across 2 E) None of the above
C) The potential difference across 1 is twice that across 2
The resistance of resistor 1 is twice the resistance of resistor 2. The two are connected in series and a potential difference is maintained across the combination. Then: A) the current in 1 twice that in 2 B) the current in 1 is half that in 2 C) the potential difference across 1 is twice that across 2 D) The potential difference 1 is half that across 2 E) none of the above are true
D) Gauss' law for magnetism
The statement that magnetic field lines form closed loops is a direct consequence of: A) Faraday's law B) Ampere's law C) Gauss' Law for electricity D) Gauss' Law for magnetism E) the Lorentz force
D) 1/2 RC
The time constant for the circuit shown in the figure is https://i.imgur.com/JJV9sun.png A) RC B) 2RC C) 4RC D) 1/2 RC E) 1/4 RC
D) 1/e
The time constant of an RC circuit is the time in which the current decreases to ________ of its initial value A) 1/10 B) 1/2 C) 1/√ 2 D) 1/e E) 1/π
A) immediately after the switch is closed
The two loops of wire shown in the figure are stacked one above the other. At which of the following times is there a clockwise current (as seen from above) in the upper loop of wire? https://i.imgur.com/pw8Oa1i.png A) immediately after the switch is closed B) all the time C) none of the others D) immediately after the switch is opened (after it has been closed for a long time) E) while the switch remains closed.
E) form closed loops
Magnetic field lines A) start on north poles and end on south poles B) start on the south poles and end on the north poles C) start on the moving positive charges and end on moving negative charges D) start on moving negative charges and end on moving charges E) form closed loops
D) 9C/16
Radio receivers are usually tuned by adjusting the capacitor in an LC circuit. If the frequency is to be increased from f to 4f /3, the capacitance must be changed from C to A) 4C/3 B) 16C/9 C) 3C/4 D) 9C/16 E) None of the others
D) one-fourth
Two identical capacitors can be connected in series or in parallel. The equivalent capacitance of the series connection is _______ the equivalent capacitance of parallel connection. A) Twice B) four times C) Half D) one-fourth E) the same as
B) the inductive reactance and the capacitive reactance are exactly equal to each other
When an RLC series circuit is driven at resonance, which of the following statements about the circuit are correct? A) the inductive reactance and capacitive reactance are both zero B) the inductive reactance and the capacitive reactance are exactly equal to each other C) the resistance is zero D) the impedance of the circuit has its maximum value E) the impedance of the circuit is zero
E) None of the surfaces mentioned-- even though Gauss's law applies in each case
Which of the following Gaussian surfaces can be used to calculate the electric field due to a uniformly-charged solid cube? A) A sphere B) a cylinder C) a cube D) none of the surfaces mentioned-- Gauss's law does not apply E) None of the surfaces mentioned-- even though Gauss's law applies in each case
B) 10^-4 m/s
Which of the following is a typical drift speed for electrons in a metallic conductor carrying a current? A) 10^8 m/s B) 10^-4 m/s C) 1 m/s D) 10^4 m/s E) Zero
B) 1.6 e
Which of the following is an impossible value of charge? A) 1.6 C B) 1.6 e C) 1 C D) 1 e
A) E= (15x-3)i
)The electric potential in a region of space is given by V = −7.5x^2 + 3x. What is the electric field in this region? A) E= (15x-3)i B) E=(-15x+3)i C) E=(-2.5x-1.5x^2)i D)E=(2.5x^3-1.5x^2)i E) E=0
E) 25 nC
A 1.0-C point charge is 15 m from a second point charge, and the electric force on one of them due to the other is 1.0 N. What is the magnitude of the second charge? A) 25 C B) 1.0 C C) 10 nC D) 25 mC E) 25 nC
C) 3
A 120-V power line is protected by a 16-A fuse. What is the maximum number of 120V, 500 W light bulbs that can be operated at full brightness from this line? A) 1 B) 2 C) 3 D) 4 E) 5
C) Q/2 and V, respectively
A battery is used to charge a parallel combination of two identical capacitors. If the potential difference across the battery terminals is V and the total charge Q flows through the battery during the charging process then the charge on the positive plate of each capacitor and the potential difference across each capacitor are: A) Q/2 and V/2, respectively B) Q and V respectively C) Q/2 and V, respectively D) Q and V/2 respectively E) 2Q and 2V, respectively
C) Q/2 and V, respectively
A battery is used to charge a parallel combination of two identical capacitors. If the potential difference across the battery terminals is V and the total charge Q flows through the battery during the charging process then the charge on the positive plate of each capacitor and the potential difference across each capacitor are: A) Q/2 and V/2, respectively B) Q and V, respectively. C) Q/2 and V, respectively D) Q and V/2, respectively, E) 2Q and 2V, respectively
C) 96 W
A battery with 24 V emf is connected to a 6.0-Ω resistor. As a result, a 4.0-A current flows through the resistor. The rate at which the battery is supplying energy to the resistor is: A) 24 W B) 144 W C) 96 W D) 864 W E) Zero
C) 18.0 W
A battery with 24V emf is connected to a 6.0 Ω resistor. As a result, a 3.0-A current flows through the resistor. The rate at which energy is being dissipated in the battery is: A) 3.0 W B) 6.0 W C) 18.0 W D) 54 W E) 72 W
D) 14 ms
A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its charge is half the final value. The time constant for the process is about: A) 5.0 ms B) 6.9 ms C) 10 ms D) 14 ms E) 20 ms
E) the author made a mistake
A certain physics textbook shows a region of space in which two electric field lines cross each other. We conclude that: A) at least two point charges are present B) an electrical conductor is present C) an insulator is present D) the field points in two directions at the same place E) the author made a mistake
E)Φ
A charge is located at the center of a spherical volume, and the flux of the electric field through the surface of the sphere is Φ. If the radius of the sphere is tripled, what would be the new flux? A) 3Φ B) Φ/3 C) 9Φ D) Φ/9 E) Φ
E) η/4
A circular disk has uniform surface charge density η. What will the surface charge density be if the radius of the disk is doubled but its total charge remains the same? Assume that the new density is also uniform. A) η B) 2 η C) 4 η D) η/2 E) η/4
A) 50 V
A conducting sphere is charged up such that the potential on its surface is 100 V (relative to infinity). If the sphere's radius were twice as large, but the charge on the sphere were the same, what would be the potential on the surface relative to infinity? A) 50 V B) 100 V C) 25 V D) 200 V E) 12.5 V
R^2
A cyclotron operates with a given magnetic field and at a given frequency. If R denotes the radius of the final orbit, the final particle energy is proportional to: A) 1/R B) R C) R^2 D) R^3 E) R^(-2)
D) proportional to r
A cylindrical region contains a uniform magnetic field that is along the cylinder axis and is changing with time. If r is the distance from the cylinder axis, the magnitude of the electric field within the region is: A) uniform B) proportional to 1/r C) proportional to 1/r^2 D) proportional to r E) proportional to r^2
B) 2R
A cylindrical wire has a resistance R and resistivity ρ. If its length and diameter are both cut in half, what will be its resistance? A) R B) 2R C) R/2 D) 4R E) R/4
A) 10^11 electrons were removed from the rod
A glass rod is charged to +6.25 nC by rubbing. Which of the following describes the transfer of charge to the rod? A) 10^11 electrons were removed from the rod B) 10^11 electrons were added to the rod C) 10^11 protons were added to the rod D) 10^11 protons were removed form the rod
C) 490 V/m
A laser with a power of 1.0 mW has a beam radius of 1.0 mm. What is the peak value of the electric field in that beam? A) 65 V/m B) 840 V/m C) 490 V/m D) 120 V/m E) 22 V/m
A) at the surface of the wire
A long straight cylindrical wire carries current I uniformly distributed over its cross section. The magnitude of the magnetic field is greatest: A) at the surface of the wire B) halfway between the center and the surface of the wire C) everywhere inside the wire, where the field is uniform D) at the center the wire E) at twice the radius of the wire
A) at the surface of the wire
A long straight cylindrical wire carries current i uniformly distributed over its cross section. The magnitude of the magnetic field is greatest: A) at the surface of the wire B) halfway between the center and the surface of the wire C) everywhere inside the wire, where the field is uniform D) at the center of the wire
A) -9.5 x 10^-5 J
A loop of current-carrying wire has a magnetic dipole moment of 5.0 x 10^-4 Am^2. If the dipole moment makes an angle of 57◦ with a magnetic field of 0.35 T. What is its potential energy A) -9.5 x 10^-5 J B) -1.5 x 10^-4 J C) -1.8 x 10^-4 J D) 1.5 x 10^-4 J E) 9.5 x 10^-5 J
A) Zero
A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7 T uniform magnetic field is parallel to the hypotenuse. The total magnetic force on the two equal sides has a magnitude of (Hint: what's the net force on any loop of current in a uniform magnetic field?): A) zero B) 0.21 N C) 0.30 N D) 0.41 N E) 0.51 N
C) the plate is negatively charged
A metal plate is connected to ground through a switch, as shown in the figure. The switch is initially closed. A charge +Q is brought close to the plate without touching it, and then the switch is opened to break the connection to ground. After the switch is opened, the charge +Q is removed. What is the charge on the plate then? https://i.imgur.com/DvVoaXF.png A) the plate is uncharged B) the plate is positively charged C) the plate is negatively charged D) the plate could be positively charged or negatively charged depending on the charge it had before +Q was brought near it E) the plate could be positively charged or negatively charged, depending on which metal it is
D) there is a rearrangement of the electrons in the ball
A neutral metal ball is suspended by a string. A positively charged insulating rod is placed near the ball, which is observed to be attracted to the rod. This is because: A) the ball is positively charged by induction B) the string is not a perfect insulator C) the ball becomes negatively charged by induction D) there is a rearrangement of the electrons in the ball
D) Energy stored in each capacitor
A parallel plate capacitor is fully charged and disconnected. If the plates are then pulled apart so that the distance between them is doubled, which of the following quantities will also double? A) charge density on each plate B) Capacitance C) Charge on each plate D) Energy stored in each capacitor E) Magnitude of the electric field
A) 1.25 x 10^13
A piece of plastic has a net charge of +2.00 µC. How many more protons than electrons does this piece of plastic have? A) 1.25 x 10^13 B) 1.25 x 10^19 C) 2.50 x 10^13 D) 2.50 x 10^19 E) Zero
D) η/2
A pipe (hollow cylinder) has uniform surface charge density η. What will the surface charge density be if the radius of the pipe is doubled but its total charge remains the same? Assume that the new density is also uniform. A) η B) 2η C) 4η D) η/2 E) η/4
E) moves towards C at increasing speed
A proton is released from rest at point B, where the potential is zero volts. The dashed lines are equipotentials. Afterward, the proton https://i.imgur.com/R3BWMaE.png A) remains at rest at B B) moves toward A with steady speed C) moves toward A with increasing speed D) moves towards C at steady speed E) moves towards C at increasing speed
C) 3.31 x 10^5 N/C
A thin, circular disk of radius 30.0 cm is oriented in the yz-plane with its center at the origin. The disk carries a total charge of +3.00 µC distributed uniformly over its surface. What is the magnitude of the electric field due to the disk at the point x = 15.0 cm along the x-axis? A) 9.95 x 10^5 N/C B) 4.98 x 10^5 N/C C) 3.31 x 10^5 N/C D) 2.49 x 10^5 N/C E) 1.99 x 10^5 N/C
A) 7.9 N/C
A very long wire carries a uniform linear charge density of 7.0 nC/m. What is the magnitude of the electric field 16.0 m from the center of the wire at a point on the wire's perpendicular bisector? A) 7.9 N/C B) 3.9 N/C C) 0.49 N/C D) 0.031 N/C
B) 2.0 A
A wire with a length of 150 m and a radius of 0.15 mm carries a current with a uniform density of 2.8 x 10^7 A/m^2. The current is A) 0.63 A B) 2.0 A C) 5.9 A D) 300 A E) 26000 A
E) 50 Ω
All the resistors shown in the figure are 20Ω. What is the effective resistance in the circuit? https://i.imgur.com/gjAE6cH.png A) 40 Ω. B) 30 Ω C) 25 Ω D) 20 Ω E) 50 Ω
E) 8m away from the wire
An very long uniformly-charged wire produces an electric field with magnitude E at a point 2 m away from it, as shown in the figure. A point (on the same vertical line) at which the field magnitude is E/4 is: https://i.imgur.com/qExOC7U.png A) 0.5 m away from the wire B) 1 m away from the wire C) 2m away from the wire D) 4m away from the wire E) 8m away from the wire
A) Yes
Can an object with no net charge have an electric field? A) Yes B) No C) only if it is an insulator D) only if it is a conductor
D) Neither I nor III
Consider the following statements, and identify the correct ones. I. When the electric field is zero at a point, the potential must also be zero there. II. If the electric potential at a point in space is zero, then the electric field at that point must also be zero. A) I only B) II only C) I and II D) Neither I nor III E) Zero
C) the drift motion of the conduction electrons due to electric fields.
Current in the metallic conductor is normally due to: A) the collective motion of all electrons in the conductor B) the thermal motion of the conduction electrons C) the drift motion of the conduction electrons due to electric fields. D) the drift motion of both electrons and positrons E) the drift motion of both electrons and protons
C) the same as the field found by Sir James
Experimenter Sir Albert (no relation to Albert Einstein) uses a test charge q0 and experimenter Sir James (no relation to James Clark Maxwell) uses a test charge 3q0 to measure an electric field produced by stationary charges. Sir Albert finds a field that is: A) greater than the field found by Sir James B) Less than the field found by Sir James C) the same as the field found by Sir James D) either greater or less than the field by Sir James, depending on the masses of the test charges
C) 2f
If the magnetic field B in a cyclotron is doubled, the frequency f of the oscillating voltage applied between the two "dee'"s of the cyclotron must be changed to A) f/2 B) f/4 C) 2f D) 4f E) No change is required
D) µ0(-2 A)
In the figure several long straight wires are shown as circles, carrying currents directly into the page or out of it. What is the loop integral of the magnetic field on path P? https://i.imgur.com/F4vgcnH.png A) µ0(18A) B) µ0(-9 A) C) µ0(2 A) D) µ0(-2 A) E) µ0 (9 A)
D) 12.4 nC
In the figure, all the charges are point-like and the charge Q in the middle is −3.10 nC. For what charge q1 will charge q2 be in static equilibrium? https://i.imgur.com/8EBtZVO.png A) -3.1 nC B) 6.20 nC C) 3.1 nC D) 12.4 nC E) -6.2 nC
D) 6 nF
In the figure, every capacitor shown is a 10 nF capacitor. The capacitance equivalent to combination is https://i.imgur.com/YmLCD5t.png A) nF B) 40 nF C) 20 nF D) 6 nF E) 15 nF
E) into the page
In the figure, the current element ids, point P, and the three vectors (1, 2, 3) are all in the plane of the page. The direction of dB at the point P due to this current element is: https://i.imgur.com/hAhYeME.png A) in the direction marked 1 B) in the direction marked 2 C) in the direction marked 3 D) out of the page E) into the page
C) charge;voltage
Series capacitors have the same _______, while parallel capacitors have the same _______. Which pair of words should fill the blanks? A) voltage;current B) charge;cirrent C) charge;voltage D) voltage;charge E) current;charge
B) -4.5 x 10^5 C
The earth has a vertical electric field at its surface, pointing down, that averages 100 N/C. This field is maintained by various atmospheric processes including lightning. The radius of the earth is 6380 km. What is the net charge on the surface of the earth? A) 4.5 x 10^5 C B) -4.5 x 10^5 C C) 4.5 x 10^-5 C D) -4.5 x 10^-5 C E) Zero
C) q1 must be negative q2 must be positive and |q1| > |q2|.
The electric field lines due to two particles, with charges of q1 and q2, are are shown in the figure below. We conclude that: https://i.imgur.com/ky1TC8x.png A) q1 must be positive q2 must be negative and |q1| > |q2|. B) q1 must be positive q2 must be negative and |q1| < |q2|. C) q1 must be negative q2 must be positive and |q1| > |q2|. D) q1 must be negative q2 must be positive and |q1| < |q2|. E) None of the other conclusions is justified by the figure
C) E= (-64z-3)k
The electric potential in a region of space is given by V = 32z^2 + 3z − 5. What is the electric field in this region? A) E= (64z + 3)k B) E= (-32x+3)k C) E= (-64z-3)k D) E=(-64z^3 - 3x^2 +5z)k E) E=0
D) decreasing;increasing
The figure below shows, in two situations, magnetic field vectors B and an induced electric field line. The magnetic fields in situations (a) and (b) are, respectively, https://i.imgur.com/Vt8bZvl.png A) increasing; increasing B) decreasing; decreasing C) increasing; decreasing D) decreasing; increasing E) None of the others-- one of these situations is inconsistent with the right hand rule
D) X is a south pole, Y is a north pole
The figure shows a bar magnet moving vertically upward toward a horizontal coil. The poles of the bar magnet are labeled X and Y. As the bar magnet approaches the coil it induces an electric current in the direction indicated on the figure (counter-clockwise as viewed from above). What are the correct polarities of the magnet? https://i.imgur.com/nQeSHkS.png A) Both X and Y are north poles B) X is a north pole, Y is a south Pole C) Both X and Y are south poles D) X is a south pole, Y is a north Pole E) The polarities of the magnet cannot be determined from the information given
E) The net force is zero; the net torque is zero
The figure shows a rectangular wire carrying a current I, located in the uniform magnetic field between the two poles shown. As you look at the loop standing at the end of the dashed line, which of the statements about the net force and net torque on the wire loop at this moment is correct? https://i.imgur.com/Avh6Y6k.png A) The net force is upward; the net torque is zero B) The net force is downward; the net torque is zero C) The net force is zero; the net torque is clockwise. D) The net force is zero; the net torque is counterclockwise E) The net force is zero; the net torque is zero
B) D
The figure shows a rod with a uniform distribution of positive charge. Which arrow shown in the figure best represents the direction of the electric field at point P? https://i.imgur.com/QS5JS6I.png A) A B) D C) C D) E E) B
A) I
The figure shows different sizes of wire made from the same Ohmic material. The radius and length of each wire are shown in the figure. Which one has the largest resistance? https://i.imgur.com/91WxuwL.png A) I B) III C) IV D) II E) cannot be determined without knowing the resistivity of the material
E) E
The figure shows three point-like charges and five Gaussian surfaces. Which surface has the largest flux of the electric field? https://i.imgur.com/9POPULI.png A) A B) B C) C D) D E) E
B) positively charged
The leaves of a positively charged electroscope separate more when an object is brought near (but not in contact with) the knob of the electroscope. The object must be: A) negatively charged B) positively charged C) uncharged D) a conductor E) an insulator
B) 1.90 µT
The magnitude of the electric field at a point P for a certain electromagnetic wave is 570 N/C. What is the magnitude of the magnetic field for that wave at P? A) 1.41 µT B) 1.90 µT C) 2.91 µT D) 2.41 µT E) 1.10 µT
D) 48
The magnitude of the flux of the electric field (24i − 30j + 16k) N/C through a 2.0 m^2 portion of the yz plane is (in units of Nm^2/C): A) 32 B) 34 C) 42 D) 48 E) 60
B) -18.0 mJ
Three point charges of −2.00 µC, 4.00 µC, and 2.00 µC are placed along the x-axis as shown in the figure. What is the change in the electric potential energy of the system if a −2.00 µC is brought in from far away and placed at point P? https://i.imgur.com/havVDEK.png A) 18.0 mJ B) -18.0 mJ C) 24.4 mJ D) -24 mJ E) Cannot be determined since no reference for the potential energy is provided
D) The net force is zero; the net torque is counterclockwise
Two long, insulated wires carry currents as shown in the figure. Which of the following statements describes the net force and net torque on the vertical wire (with current i2)? (Hint: What is the direction of the magnetic field due to i1 above and below it?) https://i.imgur.com/ptgEeZB.png A) The net force is zero; the net torque is clockwise B) The net force is to the left; the net torque is zero C) The net force is zero; the net torque is counterclockwise D) The net force is zero; the net torque is counterclockwise E) Net force and Net torque and both zero
B) perpendicular to the surface pointing outward
Two of Maxwell's equations contain an integral over a closed surface. For them the infinitesimal vector area da is always: A) tangent to the surface B) perpendicular to the surface pointing outward C) perpendicular to the surface and pointing inward D) tangent to a field line E) perpendicular to a field line
A) 8 x 10^-5 N/m, repulsive
Two parallel wires, 2 cm apart, carry currents of 2 A and 4 A respectively, in opposite directions. The force per unit length of one wire on the other is: A) 8 x 10^-5 N/m, repulsive B) 8 x 10^-5 N/m, attractive C) 4 x 10^-5 N/m, attractive D) 4 x 10^-5 N/m repulsive E) None of the above
C) 4 x 10^(-5) N/m, attractive
Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction. The force per unit length of one wire on the other is: A) 1 x 10^(-3) N/m, repulsive. B) 1 x 10^(-3) N/m, attractive C) 4 x 10^(-5) N/m, attractive D) 4 x 10^(-5) N/m, repulsive E) None of the above
E) q1 and q2 must have the same sign but may have different magnitudes
Two particles, with charges of q1 and q2, are placed a distance r apart. The electric field is zero at a point P between the particles on the line segment connecting them. We conclude that: A) P must be midway between the particles B) q1 and q2 must have the same magnitude and sign C) q1 and q2 must have equal magnitudes and opposite signs D) q1 and q2 must have opposite signs and may have different magnitudes E) q1 and q2 must have the same sign but may have different magnitudes
B) II only
Two point charges are arranged as shown. In which region could a third charge be placed so that the net electrostatic force on it is zero? https://i.imgur.com/iDNjHro.png A) I only B) II only C) I and II only D) III only E) I and III only
C) Zero
Two point charges are placed at opposite corners of a rectangle as shown in the figure. What is the potential at point A (relative to infinity) due to these charges? https://i.imgur.com/C5PZAen.png A) 12 kV B) 6.0 kV C) Zero D) -6.0 kV E) -12 kV
C) F/4
Two small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually leaks off of both spheres. When each of the spheres has lost half its initial charge, the magnitude of the electrostatic force will be A) F B) F/2 C) F/4 D) F/8 E) 2F
C) F
Two very large parallel sheets a distance d apart have their centers directly opposite each other. The sheets carry equal but opposite uniform surface charge densities. A point charge that is placed near the middle of the sheets a distance d/2 from each of them feels an electrical force F due to the sheets. If this charge is now moved closer to one of the sheets so that it is a distance d/4 from that sheet, what force will feel? A) 4F B) 2F C) F D) F/2 E) F/4
B) 7.6%
Unpolarized light passes through three polarizing filters. The first one is oriented with a horizontal transmission axis, the second filter has its transmission axis 25.7◦ from the horizontal, and the third one has a vertical transmission axis. What percent of the light gets through this combination of filters? A) 50% B) 7.6% C) 0.00% D) 92.4% E) None of the others
C) Z
an electron is initially moving to the right when it enters a uniform electric field directed upwards. Which trajectory shown below will the electron follow? https://i.imgur.com/TXUnqCm.png A) X B) Y C) Z D) W E) None of the above, the electron wont be able to enter the region with the electric field