Q&A Hero

Q: The units of the electric field are:A) N.C2B) C/NC) ND) N/CE) C/m2

Q: The diagrams show four possible orientations of an electric dipole in a uniform electric field Rank them according to the magnitude of the torque exerted on the dipole by the field, least to greatest. A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 1, 2, 4, 3 D) 3, then 2 and 4 tie, then 1 E) 1, then 2 and 4 tie, then 3

Q: An electric dipole of dipole moment 4.5 x 10-9Cm is in a 250 N/C electric field. If the electric field points east, and the dipole moment vector points 37 west of south, what is the potential energy?A) -6.8 x 10-8JB) -9.0 x 10-7JC) 0 JD) 6.8 x 10-8JE) 9.0 x 10-7J

Q: An electric dipole is oriented parallel to a uniform electric field, as shown. It is rotated to one of the five orientations shown below. Rank the final orientations according to the change in the potential energy of the dipole-field system, most negative to most positive. A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 1, 2, 4, 3 D) 3, then 2 and 4 tie, then 1 E) 1, then 2 and 4 tie, then 3

Q: The dipole moment of a dipole in a 300-N/C electric field is initially perpendicular to the field, but it rotates so it is in the same direction as the field. If the moment has a magnitude of 2 x10-9C.m the work done by the field is:A) -12 x10-7 JB) -6 x10-7JC) 0 JD) 6 x10-7JE) 12 x10-7J

Q: When the dipole moment of a dipole in a uniform electric field rotates to become more nearly aligned with the field: A) the field does positive work and the potential energy increases B) the field does positive work and the potential energy decreases C) the field does negative work and the potential energy increases D) the field does negative work and the potential energy decreases E) the field does no work

Q: A uniform electric field of 300 N/C makes an angle of 25°with the dipole moment of an electric dipole. If the torque exerted by the field has a magnitude of 2.5 x10-7N.m, the dipole moment must be:A) 8.3 x10-10C.mB) 9.2 x10-10C.mC) 2.0 x10-9C.mD) 8.3 x10-5C.mE) 1.8 x10-4C.m

Q: The torque exerted by an electric field on a dipole is: A) parallel to the field and perpendicular to the dipole moment B) parallel to both the field and dipole moment C) perpendicular to both the field and dipole moment D) parallel to the dipole moment and perpendicular to the field E) not related to the directions of the field and dipole moment

Q: An electric field exerts a torque on a dipole only if: A) the field is parallel to the dipole moment B) the field is not parallel to the dipole moment C) the field is perpendicular to the dipole moment D) the field is not perpendicular to the dipole moment E) the field is uniform

Q: The force exerted by a uniform electric field on a dipole is: A) parallel to the dipole moment B) perpendicular to the dipole moment C) parallel to the electric field D) perpendicular to the electric field E) none of the above

Q: The purpose of Milliken's oil drop experiment was to determine: A) the mass of an electron B) the charge of an electron C) the ratio of charge to mass for an electron D) the sign of the charge on an electron E) viscosity

Q: A charged oil drop with a mass of 2 x10-4kg is held suspended by a downward electric field of 300 N/C. The charge on the drop is:A) +1.5 x106CB) -1.5 x106CC) +6.5x10-6CD) -6.5 x10-6CE) 0 C

Q: An electron traveling north enters a region where the electric field is uniform and points west. The electron: A) speeds up B) slows down C) veers east D) veers west E) continues with the same speed in the same direction

Q: An electron traveling north enters a region where the electric field is uniform and points north. The electron: A) speeds up B) slows down C) veers east D) veers west E) continues with the same speed in the same direction

Q: A 200-N/C electric field is in the positive xdirection. The force on an electron in this field is:A) 200 N in the positive xdirectionB) 200 N in the negative xdirectionC) 3.2 x10-17N, in the positive xdirectionD) 3.2 x10-17N, in the negative xdirectionE) 0 N

Q: The magnitude of the force of a 400-N/C electric field on a 0.02-C point charge is:A) 8 NB) 5x10-5NC) 8 x10-3ND) 0.08 NE) 2x103N

Q: A charged particle is placed in an electric field that varies with location. No force is exerted on this charge:A) at locations where the electric field is zeroB) at locations where the electric field strength is 1/(1.6 x10-19) N/CC) if the particle is moving along a field lineD) if the particle is moving perpendicular to a field lineE) if the field is caused by an equal amount of positive and negative charge

Q: The electric field due to a uniform distribution of charge on a spherical shell is zero: A) everywhere B) nowhere C) only at the center of the shell D) only inside the shell E) only outside the shell

Q: A disk with a uniform positive surface charge density lies in the x-yplane, centered on the origin. The disk contains 2.5 x 10-6C/m2of charge, and is 7.5 cm in radius. What is the electric field at z= 15 cm? A) 30 N/C B) 300 N/C C) 3000 N/C D) 3.0 x 104N/C E) 3.0 x 107N/C

Q: A disk with a uniform positive surface charge density lies in the x-yplane, centered on the origin. Along the positive z axis, the direction of the electric field is:A) in the +z directionB) in the -z directionC) in the +xdirectionD) in the +ydirectionE) there is no field along the positive zaxis

Q: Positive charge +Q is uniformly distributed on the upper half of a rod and a negative charge -Q is uniformly distributed on the lower half. What is the direction of the electric field at point P, on the perpendicular bisector of the rod?

Q: Positive charge +Qis uniformly distributed on the upper half of a semicircular rod and negative charge "Qis uniformly distributed on the lower half. What is the direction of the electric field at point P, the center of the semicircle? A)  B)  C)  D)  E)

Q: Positive charge Qis uniformly distributed on a semicircular rod. What is the direction of the electric field at point P, the center of the semicircle? A)  B)  C)  D)  E)

Q: A cylinder has a radius of 2.1 cm and a length of 8.8 cm. Total charge 6.1 x10-7C is distributed uniformly throughout. The volume charge density is:A) 7.4 x10-11C/m3B) 5.3 x10-5C/m3C) 5.3 x10-5C/m2D) 8.5 x10-4C/m3E) 5.0 x10-3C/m3

Q: A spherical shell has an inner radius of 3.7 cm and an outer radius of 4.5 cm. If charge is distributed uniformly throughout the shell with a volume density of 6.1 x10-4C/m3the total charge is:A) 1.0 x10-7CB) 1.3 x10-7CC) 2.0 x10-7CD) 1.7x10-6CE) 5.0 x10-6C

Q: Charge is placed on the surface of a 2.7-cm radius isolated conducting sphere. The surface charge density is uniform and has the value 6.9 x10-6C/m2. The total charge on the sphere is:A) 5.7x10-10CB) 1.6x10-8CC) 3.2x10-8CD) 6.3 x10-8CE) 7.5 x10-4C

Q: A total charge of 6.3 x10-8C is distributed uniformly throughout a 2.7-cm radius sphere. The volume charge density is:A) 3.7 x10-7C/m3B) 6.9 x10-6C/m3C) 6.9 x10-6C/m2D) 2.5 x10-4C/m3E) 7.6 x10-4C/m3

Q: An electric dipole consists of two charges, 2.5 C, separated by 1.0 x 10-4m and centered on the origin. If the dipole is oriented along the xaxis, what is the electric field at x= 15 cm? A) 0 N/C B) 100 N/C C) 200 N/C D) 670 N/C E) 1300 N/C

Q: An electric dipole consists of a particle with a charge of +6 x10-6C at the origin and a particle with a charge of -6 x10-6C on the xaxis at x= 3 x10-3m. Its dipole moment is:A) 1.8 x10-8C.m, in the positive xdirectionB) 1.8 x10-8C.m, in the negative xdirectionC) 0 C.m, because the net charge is 0D) 1.8 x10-8C.m, in the positive ydirectionE) 1.8 x10-8C.m, in the negative ydirection

Q: Comparing the field of a single point charge with the field of an electric dipole, A) the field of the point charge decreases more rapidly with distance B) the field of the point charge decreases less rapidly with distance C) the field of the point charge decreases more rapidly with distance but only along the dipole axis D) the field of the point charge decreases less rapidly with distance but only perpendicular to the dipole axis E) the fields decrease equally rapidly with distance

Q: An electric dipole consists of a particle with a charge of +6 x10-6C at the origin and a particle with a charge of -6 x10-6C on the xaxis at x= 3 x10-3m. The direction of the electric field due to the dipole at points on the xaxis is:A) in the positive xdirectionB) in the negative xdirectionC) in the positive ydirectionD) in the negative ydirectionE) in the positive xdirection between the charges and in the negative xdirection elsewhere

Q: Two point charges are arranged as shown. In which region could a third charge +1 C be placed so that the net electrostatic force on it is zero? A) I only B) I and II only C) III only D) I and III only E) II only

Q: Two point particles, with the same charge, are located at two vertices of an equilateral triangle. A third charged particle is placed so the electric field at the third vertex is zero. The third particle must: A) be on the perpendicular bisector of the line joining the first two charges B) be on the line joining the first two charges C) be identical to the first two charges D) have the same magnitude as the first two charges but may have a different sign E) be at the center of the triangle

Q: Two charged point particles are located at two vertices of an equilateral triangle and the electric field is zero at the third vertex. We conclude: A) the two particles have charges with opposite signs and the same magnitude B) the two particles have charges with opposite signs and different magnitudes C) the two particles have identical charges D) the two particles have charges with the same sign but different magnitudes E) at least one other charged particle is present

Q: Two point particles, one with charge +8 x10-9C and the other with chargep-2 x10-9C, are separated by 4 m. The electric field midway between them is:A) 9 x109N/CB) 13,500 N/CC) 135,000 N/CD) 36 x10-9N/CE) 22.5 N/C

Q: The diagram shows two identical particles, each with positive charge Q. The electric field at point P on the perpendicular bisector of the line joining them is: A)  B)  C)  D)  E) zero

Q: A nucleus of carbon 14 has 6 protons and 8 neutrons. The atomic number and mass number of carbon 14 are, respectively, A) 6 and 8 B) 6 and 14 C) 8 and 14 D) 14 and 20 E) 14 and 22

Q: One type of medical imaging process is called positron emission tomography. Radioactive material is injected into a patient; during the radioactive decay the material emits a positron, which then interacts with an atomic electron, emitting gamma rays, which are detected by the imager. This gamma ray emission process is called: A) pair production B) annihilation C) absorption D) alpha decay E) fission

Q: Is it ever possible for the following process to occur? -> e+ + e-+ e+A) Yes, it is.B) No, this process does not conserve energy.C) No, this process does not conserve momentum.D) No, this process does not conserve mass.E) No, this process does not conserve electric charge.

Q: Which of the following is NOT a possible value for the electric charge on an object? A) 8 x 10-20C B) 8 x 10-19C C) 8 x 10-18C D) 8 x 10-17C E) 8 x 10-16C

Q: A wire contains a steady current of 2 A. The number of electrons that pass a cross section in 2 s is:A) 2B) 4C) 6.3 x1018D) 1.3 x1019E) 2.5 x1019

Q: The magnitude of the total negative charge on the electrons in 1 kg of helium (atomic number 2, atomic mass 4) is:A) 48 CB) 2.4 x107CC) 4.8 x107CD) 9.6 x107CE) 1.9 x108C

Q: The magnitude of the total negative charge on the electrons in 1 mol of helium (atomic number 2, atomic mass 4) is:A) 4.8 x104CB) 9.6 x104CC) 1.9 x105CD) 3.8 x105CE) 7.7 x105C

Q: The magnitude of the charge on an electron is approximately:A) 1023CB) 10-23CC) 1019CD) 10-19CE) 109C

Q: A wire contains a steady current of 2 A. The charge that passes a cross section in 2 s is:A) 3.2 x10-19CB) 6.4 x10-19CC) 1 CD) 2 CE) 4 C

Q: A kiloampere.hour is a unit of:A) currentB) charge per timeC) powerD) chargeE) energy

Q: A coulomb is the same as:A) an ampere/secondB) half an ampere .second2C) an ampere/meter2D) an ampere .secondE) a newton .meter2

Q: If excess charge is put on a spherical nonconductor, A) it remains where it was placed B) it spreads a little from where it was placed but not over the whole sphere C) it spreads uniformly over the surface of the sphere if the sphere is small D) it spreads uniformly throughout the volume of the conductor E) it spreads uniformly over the surface of the sphere

Q: Two identical conducting spheres A and B carry equal charge and exert electrostatic forces of magnitude Fon each other. They are separated by a distance much larger than their diameters. A third identical conducting sphere C is uncharged. Sphere C is first touched to A, then to B, and finally removed. As a result, the electrostatic force between A and Bbecomes: A) F/2 B) F/4 C) 3F/8 D) F/16 E) 0

Q: A positively charged metal sphere A is brought into contact with an uncharged metal sphere B. As a result: A) both spheres are positively charged B) A is positively charged and B is neutral C) A is positively charged and B is negatively charged D) A is neutral and B is positively charged E) A is neutral and B is negatively charged

Q: Two uncharged metal spheres, L and M, are in contact. A negatively charged rod is brought close to L, but not touching it, as shown. The two spheres are slightly separated and the rod is then withdrawn. As a result: A) both spheres are neutral B) both spheres are positive C) both spheres are negative D) L is negative and M is positive E) L is positive and M is negative

Q: If excess charge is put on a spherical conductor, A) it remains where it was placed B) it spreads a little from where it was placed but not over the whole sphere C) it spreads uniformly over the surface of the sphere if the sphere is small D) it spreads uniformly throughout the volume of the conductor E) it spreads uniformly over the surface of the sphere

Q: Charge is distributed uniformly on the surface of a spherical nonconducting shell. A point particle with charge qis inside. The electrical force on the particle qis least when: A) it is near the inside surface of the shell B) it is at the center of the shell C) it is halfway between the shell center and the inside surface D) it is near, but not at, the center of the shell E) all of the above (the force is zero everywhere inside)

Q: Charge is distributed uniformly on the surface of a spherical balloon (an insulator). A point particle with charge qis inside. The electrical force on the particle qis greatest when: A) it is just outside the surface of the balloon B) it is at the center of the balloon C) it is halfway between the balloon center and the inside surface D) it is anywhere inside (the force is same everywhere and is not zero) E) it is anywhere inside (the force is zero everywhere)

Q: Two particles, each with charge Q, and a third particle, with a charge q,are placed at the vertices of an equilateral triangle as shown. The total force on the particle with charge qis: A) Parallel to the left side of the triangle B) Parallel to the right side of the triangle C) Parallel to the bottom side of the triangle D) perpendicular to the bottom side of the triangle E) perpendicular to the left side of the triangle

Q: A charge Qis spread uniformly along the circumference of a circle of radius R. A point particle with charge qis placed at the center of this circle. The total force exerted on the particle qcan be calculated by Coulomb's law:A) if you use Rfor the distanceB) if you use 2Rfor the distanceC) if you use 2Rfor the distanceD) and the result of the calculation is zeroE) none of the above

Q: A particle with charge is placed at the origin. An identical particle, with the same charge, is placed 2 m from the origin on the x axis, and a third identical particle, with the same charge, is placed 2 m from the origin on the yaxis. The magnitude of the force on the particle at the origin is:

Q: Two particles A and B have identical charge Q. For a net force of zero to be exerted on a third charged particle it must be placed: A) midway between A and B B) on the perpendicular bisector of the line joining A and B but away from the line C) on the line joining A and B, not between the particles D) on the line joining A and B, closer to one of them than the other E) at none of these places (there is no place)

Q: Particle 1 with charge q1, and particle 2, with a charge q2, are on the x axis, with particle 1 at x = awith and particle 2 at x= -2a. For the net force on a third charged particle, at the origin to be zero q1and q2must be related by q2=:A) 2q1B) 4q1C) -2q1D) -4q1E) -q1/4

Q: Two particles have charges Qand -Q(equal magnitude and opposite sign). For a net force of zero to be exerted on a third charge it must be placed:A) midway between Qand -QB) on the perpendicular bisector of the line joining Qand -Q, but not on that line itselfC) on the line joining Qand -Q, to the side of Qopposite -QD) on the line joining Qand -Q, to the side of -Qopposite QE) at none of these places (there is no place)

Q: Two protons (p1and p2) and an electron (e) lie on a straight line, as shown. The directions of the force of p1on e, the force of p2on e, and the total force on e, respectively, are: A) , ,  B) , ,  C) , ,  D) , ,  E) , , 

Q: Two electrons (e1and e2) and aproton (p) lie on a straight line, as shown. The directions of the force of e2on e1, the force of pon e1, and the total force on e1, respectively, are: A) , ,  B) , ,  C) , ,  D) , ,  E) , , 

Q: To what types of electrically charged objects does Coulomb's law apply? A) only pointlike particles B) any symmetric objects C) it applies to all such objects D) only pointlike particles and objects that can be treated as particles E) it applies to all such objects as long as they are not moving

Q: A particle with a charge of 5 x10-6C and a mass of 20 g moves uniformly with a speed of 7 m/s in a circular orbit around a stationary particle with a charge of -5 x10-6C. The radius of the orbit is:A) 0 mB) 0.23 mC) 0.62 mD) 1.6 mE) 4.4 m

Q: In the Rutherford model of the hydrogen atom, a proton (mass M, charge Q) is the nucleus and an electron (mass m, charge q) moves around the proton in a circle of radius r. Let kdenote the Coulomb force constant and Gthe universal gravitational constant. The ratio of the electrostatic force to the gravitational force between electron and proton is:A) kQq/GMmr2B) GQq/kMmC) kMm/GQqD) GMm/kQqE) kQq/GMm

Q: A particle with charge Qis on the yaxis a distance afrom the origin and a particle with charge qis on the xaxis a distance dfrom the origin. The value of dfor which the xcomponent of the force on the second particle is the greatest is: A) 0 B) a C) D) a/2 E)

Q: Two identical charges, 2.0 m apart, exert forces of magnitude 4.0 N on each other. The value of either charge is:A) 1.8 x10-9CB) 2.1 x10-5CC) 4.2 x10-5CD) 1.9 x105CE) 3.8 x105C

Q: A 5.0-C charge is 10 m from a -2.0-C charge. The electrostatic force is on the positive charge is:A) 9.0 x108N toward the negative chargeB) 9.0 x108N away from the negative chargeC) 9.0 x109N toward the negative chargeD) 9.0 x109N away from the negative chargeE) none of these

Q: Two particles, X and Y, are 4 m apart. X has a charge of 2Qand Y has a charge of Q. The force of X on Y: A) has twice the magnitude of the force of Y on X B) has half the magnitude of the force of Y on X C) has four times the magnitude of the force of Y on X D) has one-fourth the magnitude of the force of Y on X E) has the same magnitude as the force of Y on X

Q: Two small charged objects repel each other with a force Fwhen separated by a distance d. If the charge on each object is reduced to one-fourth of its original value and the distance between them is reduced to d/2 the force becomes: A) F/16 B) F/8 C) F/4 D) F/2 E) F

Q: A small object has charge Q.Charge qis removed from it and placed on a second small object. The two objects are placed 1 m apart. For the force that each object exerts on the other to be a maximum, qshould be: A) 2Q B) Q C) Q/2 D) Q/4 E) 0

Q: The diagram shows two pairs of highly charged plastic cubes. Cubes 1 and 2 attract each and cubes 1 and 3 repel each other. Which of the following illustrates the forces of cube 2 on 3 and cube 3 on 2? A) I B) II C) III D) IV E) V

Q: A positively charged insulating rod is brought close to an object that is suspended by a string. If the object is repelled away from the rod we can conclude: A) the object is positively charged B) the object is negatively charged C) the object is an insulator D) the object is a conductor E) none of the above

Q: A positively charged insulating rod is brought close to an object that is suspended by a string. If the object is attracted toward the rod we can conclude: A) the object is positively charged B) the object is negatively charged C) the object is an insulator D) the object is a conductor E) none of the above

Q: Consider the following procedural steps: (1) ground the electroscope (2) remove the ground from the electroscope (3) touch a charged rod to the electroscope (4) bring a charged rod near, but not touching, the electroscope (5) remove the charged rod To charge an electroscope by induction, use the sequence: A) 1, 4, 5, 2 B) 4, 1, 2, 5 C) 3, 1, 2, 5 D) 4, 1, 5, 2 E) 3, 5

Q: An electroscope is charged by induction using a glass rod that has been made positive by rubbing it with silk. The electroscope leaves: A) gain electrons B) gain protons C) lose electrons D) lose protons E) gain an equal number of protons and electrons

Q: A negatively charged rubber rod is brought near the knob of a positively charged electroscope. The result is that: A) electroscope leaves will move farther apart B) the rod will lose its charge C) electroscope leaves will tend to collapse D) electroscope will become discharged E) nothing noticeable will happen

Q: The leaves of a positively charged electroscope diverge more when an object is brought near the knob of the electroscope. The object must be: A) a conductor B) an insulator C) positively charged D) negatively charged E) uncharged

Q: The diagram shows a pair of highly charged plastic cubes that attract each other. Cube 3 is a conductor and is uncharged. Which of the following illustrates the forces between cubes1 and 3 and between cubes 2 and 3? A) I B) II C) III D) IV E) V

Q: To make an uncharged object have a positive charge: A) remove some neutrons B) add some neutrons C) add some electrons D) remove some electrons E) heat it to cause a change of phase