Q&A Hero

Q: Let Qdenote charge, Vdenote potential difference and Udenote stored energy. Of these quantities, capacitors in parallel must have the same: A) Qonly B) Vonly C) Uonly D) Qand Uonly E) Vand Uonly

Q: Let Qdenote charge, Vdenote potential difference and Udenote stored energy. Of these quantities, capacitors in series must have the same: A) Qonly B) Vonly C) Uonly D) Qand Uonly E) Vand Uonly

Q: Capacitor C1is connected alone to a battery and charged until the magnitude of the charge on each plate is 4.0x10-8 C. Then it is removed from the battery and connected to two other capacitors C2 and C3, as shown. The charge on the positive plate of C1is then 1.0 x10-­8 C. The charges on the positive plates of C2and C3 are:

Q: Two parallel-plate capacitors with the same plate separation but different capacitance are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is NOT the same for both capacitors when they are fully charged is: A) potential difference B) energy density C) electric field between the plates D) charge on the positive plate E) dielectric constant

Q: Each of the three 25-F capacitors shown is initially uncharged. How many coulombs of charge pass through the ammeter A after the switch S is closed? A) 0.033 C B) 0.10 C C) 0.30 C D) 10 C E) none of these

Q: The diagram shows six 6-F capacitors. The capacitance between points a and b is:

Q: Two identical capacitors, each with capacitance C, are connected in parallel and the combination is connected in series to a third identical capacitor. The equivalent capacitance of this arrangement is: A) 2C/3 B) C C) 3C/2 D) 2C E) 3C

Q: A battery is used to charge a series combination of two identical capacitors. If the potential difference across the battery terminals is Vand total charge Qflows 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) Qand V, respectively C) Q/2 and V, respectively D) Qand V/2, respectively E) Qand 2V, respectively

Q: Capacitors C1and C2are connected in parallel and a potential difference is applied to the combination. If the capacitor that is equivalent to the combination has the same potential difference, then the charge on the equivalent capacitor is the same as: A) the charge on C1 B) the sum of the charges on C1and C2 C) the difference of the charges on C1and C2 D) the product of the charges on C1and C2 E) none of the above

Q: A 2-F and a 1-F capacitor are connected in series and charged from a battery. They store charges Pand Q, respectively. When disconnected and charged separately using the same battery, they have charges Rand S, respectively. Then: A) R>S>Q= P B) P>Q>R= S C) R>P= Q>S D) R= P>S= Q E) R>P>S= Q

Q: Two identical capacitors are connected in series and two, each identical to the first, are connected 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

Q: Capacitors C1and C2are connected in series. The equivalent capacitance is given by: A) C1C2/(C1+ C2) B) (C1+ C2)/C1C2 C) 1/(C1+ C2) D) C1/C2 E) C1+ C2

Q: Capacitors C1and C2are connected in series and a potential difference is applied to the combination. If the capacitor that is equivalent to the combination has the same potential difference, then the charge on the equivalent capacitor is the same as: A) the charge on C1 B) the sum of the charges on C1and C2 C) the difference of the charges on C1and C2 D) the product of the charges on C1and C2 E) none of the above

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Q: A battery is used to charge a parallel combination of two identical capacitors. If the potential difference across the battery terminals is Vand the total charge Qflows 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) Qand V, respectively C) Q/2 and V, respectively D) Qand V/2, respectively E) Qand 2V, respectively

Q: Capacitor C1and C2are connected in parallel. The equivalent capacitance is given by: A) C1C2/(C1+ C2) B) (C1+ C2)/C1C2 C) 1/(C1+ C2) D) C1/C2 E) C1+ C2

Q: Two parallel-plate capacitors with different capacitance but the same plate separation are connected in series to a battery. Both capacitors are filled with air. The quantity that is the same for both capacitors when they are fully charged is: A) potential difference B) stored energy C) energy density D) electric field between the plates E) charge on the positive plate

Q: Two parallel-plate capacitors with different plate separation but the same capacitance are connected in series to a battery. Both capacitors are filled with air. The quantity that is NOT the same for both capacitors when they are fully charged is: A) potential difference B) stored energy C) electric field between the plates D) charge on the positive plate E) dielectric constant

Q: Two parallel-plate capacitors with the same plate area but different capacitance are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is the same for both capacitors when they are fully charged is: A) potential difference B) energy density C) electric field between the plates D) charge on the positive plate E) plate separation

Q: Each of the four capacitors shown is 500 . The voltmeter reads 1000V. The magnitude of the charge on each capacitor plate is:A) 0.2 CB) 0.5 CC) 20 CD) 50 CE) none of these

Q: A parallel-plate capacitor has a plate area of 0.3 m2and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 5 x10-6C then the force exerted by one plate on the other has a magnitude of about:A) 5 NB) 9 NC) 1 x104ND) 9 x105NE) 2 x107N

Q: Two conducting spheres have radii of R1and R2with R1greater than R2. If they are far apart the capacitance is proportional to:A) R1R2/(R1- R2)B) C) (R1- R2)/R1R2D) E) none of these

Q: The capacitance of a cylindrical capacitor can be increased by: A) decreasing both the radius of the inner cylinder and the length B) increasing both the radius of the inner cylinder and the length C) increasing the radius of the outer cylindrical shell and decreasing the length D) decreasing the radius of the inner cylinder and increasing the radius of the outer cylindrical shell E) only by decreasing the length

Q: The capacitance of a single isolated spherical conductor with radius Ris proportional to: A) R B) R2 C) 1/R D) 1/R2 E) none of these

Q: The capacitance of a spherical capacitor with inner radius aand outer radius bis proportional to:A) a/bB) b- aC) b2- a2D) ab/(b- a)E) ab/(b2- a2)

Q: A parallel-plate capacitor has a plate area of 0.2 m2and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4 x10-6C the potential difference across the plates is approximately:A) 0 VB) 4 x10-2VC) 2 x102VD) 2 x105VE) 4 x108V

Q: A parallel-plate capacitor has a plate area of 0.2 m2and a plate separation of 0.1 mm. To obtain an electric field of 2.0 x106V/m between the plates, the magnitude of the charge on each plate should be:A) 3.5 x10-6 CB) 7.1 x10-6 CC) 1.4 x10-5 CD) 1.8 x10-5 CE) 8.9 x10-5 C

Q: Pulling the plates of an isolated charged capacitor apart: A) increases the capacitance B) increases the potential difference C) does not affect the potential difference D) decreases the potential difference E) does not affect the capacitance

Q: If the plate separation of an isolated charged parallel-plate capacitor is doubled: A) the electric field is doubled B) the potential difference is halved C) the charge on each plate is halved D) the surface charge density on each plate is doubled E) none of the above

Q: If the plate area of an isolated charged parallel-plate capacitor is doubled: A) the electric field is doubled B) the potential difference is halved C) the charge on each plate is halved D) the surface charge density on each plate is doubled E) none of the above

Q: If both the plate area and the plate separation of a parallel-plate capacitor are doubled, the capacitance is: A) doubled B) halved C) unchanged D) one-fourth the original E) quadrupled

Q: 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 separation E) decreasing the plate area

Q: The plate areas and plate separations of five parallel plate capacitors are capacitor 1: area A0, separation d0 capacitor 2: area 2A0, separation 2d0 capacitor 3: area 2A0, separation d0/2 capacitor 4: area A0/2, separation 2d0 capacitor 5: area A0, separation d0/2 Rank these according to their capacitances, least to greatest. A) 1, 2, 3, 4, 5 B) 5, 4, 3, 2, 1 C) 5, then 3 and 4 tie, then 1, then 2 D) 4, then 1 and 2 tie, then 5, then 3 E) 3, then 5, then 1 and 2 tie,then 4

Q: The capacitance of a parallel-plate capacitor is: A) proportional to the plate area B) proportional to the charge stored C) independent of any material inserted between the plates D) proportional to the potential difference of the plates E) proportional to the plate separation

Q: The capacitance of a parallel-plate capacitor with plate area Aand plate separation dis given by:

Q: If the charge on a parallel-plate capacitor is doubled: A) the capacitance is halved B) the capacitance is doubled C) the electric field is halved D) the electric field is doubled E) the surface charge density is not changed on either plate

Q: To charge a 1-F capacitor with 2 C requires a potential difference of: A) 0.2 V B) 0.5 V C) 2 V D) 5 V E) none of these

Q: Each plate of a capacitor stores a charge of magnitude 1 mC when a 100-V potential difference is applied. The capacitance is:E) none of these

Q: A parallel-plate capacitor C has a charge Q. The actual charges on its plates are:A) Q, QB) Q/2, Q/2C) Q, -QD) Q/2, -Q/2E) Q, 0

Q: A farad is the same as a: A) J/V B) V/J C) C/V D) V/C E) N/C

Q: The units of capacitance are equivalent to: A) J/C B) V/C C) J2/C D) C/J E) C2/J

Q: A conducting sphere has charge Qand its electric potential is V, relative to the potential far away. If the charge is doubled to 2Q, the potential is: A) V B) 2V C) 4V D) V/2 E) V/4

Q: A 5-cm radius isolated conducting sphere is charged so its potential is +100 V, relative to the potential far away. The charge density on its surface is:A) +2.2 x10-7C/m2B) -2.2 x10-7C/m2C) +3.5 x10-7C/m2D) -3.5 x10-7C/m2E) +1.8 x10-8C/m2

Q: A solid metal sphere carries a charge of 5 x10-9C and is at a potential of 400 V, relative to the potential far away. The potential at the center of the sphere is:A) 400 VB) -400 VC) 2 x10-6VD) 0 VE) none of these

Q: Two conducting spheres are far apart. The smaller sphere carries a total charge of Q. The larger sphere has a radius that is twice that of the smaller and is neutral. After the two spheres are connected by a conducting wire, the charges on the smaller and larger spheres, respectively, are: A) Q/2 and Q/2 B) Q/3 and 2Q/3 C) 2Q/3 and Q/3 D) 0 and Q E) 2Qand "Q

Q: A hollow metal sphere is charged to a potential V. The potential at its center is:A) VB) 0C) -VD) 2VE)

Q: A 5-cm radius conducting sphere has a charge density of 2 x10-6C/m2on its surface. Its electric potential, relative to the potential far away, is:A) 1.1 x104VB) 2.2 x104VC) 2.3 x105VD) 3.6 x105VE) 7.2 x106V

Q: A conducting sphere with radius R is charged until the magnitude of the electric field just outside its surface is E. The electric potential of the sphere, relative to the potential for away, is: A) 0 B) E/R C) E/R2 D) ER E) ER2

Q: Two conducting spheres, one having twice the diameter of the other, are separated by a distance large compared to their diameters. The smaller sphere (1) has charge qand the larger sphere (2) is uncharged. If the spheres are connected by a long thin wire and come to equilibrium: A) 1 and 2 have the same potential B) 2 has twice the potential of 1 C) 2 has half the potential of 1 D) 1 and 2 have the same charge E) all of the charge is dissipated

Q: An electric dipole consists of two equal and opposite charged particles of mass 1.2 g and charge 3.7 C separated by 1.7 mm. What is the escape speed of the positive charge - that is, how much speed would you have to give it so it would escape the other charge?A) 200 m/sB) 350 m/sC) 6600 m/sD) 7.1 x 104m/sE) 2.0 x 105m/s

Q: Points R and T are each a distance dfrom each of two equal positive charges as shown. If k= , the work required to move a particle with a charge qfrom R to T is:A) 0B) kQq/d2C) kQq/dD) E) kQq/(2d)

Q: Points R and T are each a distance dfrom each of two particles with charges of equal magnitudes and opposite signs as shown. If , the work required to move a particle with negative charge qfrom R to T is:A) 0B) kqQ/d2C) kqQ/dD) E) kQq/(2d)

Q: Three possible configurations for an electron e and a proton p are shown below. Take the zero of potential to be at infinity and rank the three configurations according to the potential at S, from most negative to most positive. A) 1, 2, 3 B) 3, 2, 1 C) 2, 3, 1 D) 1 and 2 tie, then 3 E) 1 and 3 tie, then 2

Q: Two identical particles, each with charge q,are placed on the xaxis, one at the origin and the other at x= 5 cm. A third particle, with charge -q, is placed on the x axis so the potential energy of the three-particle system is the same as the potential energy when they are all infinitely far apart. Its x coordinate is:A) 13 cmB) 2.5 cmC) 7.5 cmD) 10 cmE) -5 cm

Q: Three particles lie on the xaxis: particle 1, with a charge of 1 x10-8C is at x= 1 cm, particle 2, with a charge of 2x10"8C, is at x= 2 cm, and particle 3, with a charge of -3 x10-8C, is at x= 3 cm. The potential energy of this arrangement, relative to the potential energy for infinite separation, is:A) +4.9 x10-4JB) -­4.9 x10-4JC) +8.5 x10-4JD) -­8.5x10-4JE) 0 J

Q: A particle with a charge of 5.5 x10-8C charge is fixed at the origin. A particle with a charge of"2.3 x10-8C charge is moved from x= 3.5 cm on the xaxis to y= 3.5 cm on the yaxis. The change in the potential energy of the two-charge system is:A) 3.2 x10-4JB) -3.2 x10-4JC) 9.3 x10-3JD) -9.3 x10-3JE) 0 J

Q: A particle with a charge of 5.5 x10-8C is fixed at the origin. A particle with a charge of -2.3 x10-8C is moved from x= 3.5 cm on the x axis to y= 4.3 cm on the y axis. The change in potential energy of the two-particle system is:A) 3.1 x10-3JB) -3.1 x10-3JC) 6.0 x10-5JD) -6.0 x10-5JE) 0 J

Q: A particle with a charge of 5.5 ï‚´10"6C is 3.5 cm from a particle with a charge of "2.3 ï‚´10"8C. The potential energy of this two-particle system, relative to the potential energy at infinite separation, is: A) 3.3ï‚´10"2J B) "3.3ï‚´10"2J C) 9.3 ï‚´10"1J D) "9.3 ï‚´10"1J E) 0 J

Q: Choose the correct statement: A) A proton tends to go from a region of low potential to a region of high potential B) The potential of a negatively charged conductor must be negative C) If = 0 at a point P then Vmust be zero at P D) If V = 0 at a point P then must be zero at P E) None of the above is correct

Q: In a certain region of space the electric potential increases uniformly from east to west and does not vary in any other direction. The electric field: A) points east and varies with position B) points east and does not vary with position C) points west and varies with position D) points west and does not vary with position E) points north and does not vary with position

Q: A geologist measures the Earth's electric field near the surface, and finds that equipotential lines 100 V apart are at a distance of 75 cm from each other. Assuming the electric field is uniform, what is its magnitude? A) 130 V/m B) 100 V/m C) 75 V/m D) 1.3 V/m E) 0.75 V/m

Q: The graph shows the electric potential as a function of xin a certain region. What is thexcomponent of the electric field in this region if Vs= 50 V?A) 250 V/mB) 40 V/mC) 10 V/mD) -40 V/mE) -250 V/m

Q: The electric potential at a certain point is given by V= -7.5x2+ 3x, where Vis in volts and xis in meters. What is the electric field at that point?A) = (15x- 3)B) = (-15x+ 3)C) = (-2.5x3+ 1.5 x2)D) = (2.5x3- 1.5 x2)E) = 0

Q: The electric potential in a certain region of space is given by V= -7.5x2+ 3x, where Vis in volts and x is in meters. In this region the equipotential surfaces are:A) planes parallel to the xaxisB) planes parallel to the yzplaneC) concentric spheres centered at the originD) concentric cylinders with the xaxis as the cylinder axisE) unknown unless the charge is given

Q: A wire carrying a charge density of C/m is bent into a circle of radius r. What is the electric potential at the center of the circle?

Q: Compared to the magnitude of the electric potential far from a point charge, the magnitude of the electric potential far from an electric dipole: A) decreases more slowly with distance B) decreases more quickly with distance C) increases more slowly with distance D) increases more quickly with distance E) varies in the same way with distance

Q: In the diagram, the points 1, 2, and 3 are all the same very large distance from a dipole. Rank the points according to the values of the electric potential at them, from the most negative to the most positive. A) 1, 2, 3 B) 3, 2, 1 C) 2, 3, 1 D) 1, 3, 2 E) 1 and 2 tie, then 3

Q: Equipotential surfaces associated with an electric dipole are: A) spheres centered on the dipole B) cylinders with axes along the dipole moment C) planes perpendicular to the dipole moment D) planes parallel to the dipole moment E) none of the above

Q: A particle with charge qis to be brought from far away to a point near an electric dipole. No work is done if the final position of the particle is on:A) the line through the charges of the dipoleB) a line that is perpendicular to the dipole momentC) a line that makes an angle of 45°with the dipole momentD) a line that makes an angle of 30°with the dipole momentE) none of the above

Q: The equipotential surfaces associated with a charged point particle are: A) radially outward from the particle B) vertical planes C) horizontal planes D) concentric spheres centered at the particle E) concentric cylinders with the particle on the axis

Q: Two particles with charges Qand -Qare fixed at the vertices of an equilateral triangle with sides of length a. If , the work required to move a particle with a charge q from the other vertex to the center of the line joining the fixed charges is:A) 0B) kQq/aC) kQq/a2D) 2kQq/aE)

Q: Eight identical spherical raindrops are each at a potential V, relative to the potential far away. They coalesce to make one spherical raindrop whose potential is: A) V/8 B) V/2 C) 2V D) 4V E) 8V

Q: A total charge of 7 x10-8C is uniformly distributed throughout a non-conducting sphere with a radius of 5 cm. The electric potential at the surface, relative to the potential far away, is about:A) -1.3 x104VB) 1.3 x104VC) 630 VD) 130 VE) 0 V

Q: Positive charge is distributed uniformly throughout a non-conducting sphere. The highest electric potential occurs: A) at the center B) at the surface C) halfway between the center and surface D) just outside the surface E) far from the sphere

Q: In separate experiments, four different particles each start from far away with the same speed and impinge directly on a gold nucleus. The masses and charges of the particles are particle 1: mass m0, charge q0 particle 2: mass 2m0, charge 2q0 particle 3: mass 2m0, charge q0/2 particle 4: mass m0/2, charge 2q0 Rank the particles according to the distance of closest approach to the gold nucleus, from smallest to largest. A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 3, then 1 and 2 tie, then 4 D) 4, then 1 and 2 tie, then 3 E) 1 and 2 tie, then 3, then 4

Q: The graph shows the electric field as a function of position in a particular region of space. If Exs= 100 N/C, what is the potential difference between x= 3 m and x= 6 m?A) 250 VB) 50 VC) 0 VD) -50 VE) -250 V

Q: The potential difference between the ends of a 2-meter stick that is parallel to a uniform electric field is 400 V. The magnitude of the electric field is: A) 0 V/m B) 100 V/m C) 200 V/m D) 400 V/m E) 800 V/m

Q: The diagram shows four pairs of large parallel conducting plates. The value of the electric potential is given for each plate. Rank the pairs according to the magnitude of the electric field between the plates, least to greatest. A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 2, 3, 1, 4 D) 2, 4, 1, 3 E) 3, 2, 4, 1

Q: If the electric field is in the positive x direction and has a magnitude given by E= Cx2, where Cis a constant, then the electric potential is given by V=A) 2CxB) -2CxC) Cx3/3D) -Cx3/3E) -3Cx3