exam II: ch.18, 19, 20
a) positive
(q1+ --> q2+ --> q3-) a gaussian surface encloses q2. the net flux on the surface is a) positive b) negative c) zero d) depends on the size of the three charges
b) q2
(q1+ --> q2+ --> q3-) now assume q1 and q2 are equal in charge. which one applies a larger force on q3? a) q1 b) q2 c) they apply the same force d) need to know the size of q3
d) they are the same
(q1+ --> q2+ --> q3-) say q2 has twice the charge of q3. which magnitude of force is bigger, F23 (force by q2 on q3) or F32 (force by q3 on q2)? a) no way to know without knowing the exact distances b) F23 c) F32 d) they are the same
a) right
(q1+ --> q2+ --> q3-) what is the direction of the force on q2 due to q3? a) right b) left c) up d) down e) there is no force on q2 due to q3
a) right
(q1+ --> q2+ --> q3-) what is the direction of the net electric field on the line connecting q2 and q3? a) right b) left c) up d) down e) the direction of the arrow changes as you move along the line
b) 71V
A "defibrillator" is a medical device used to supply electrical energy to a stopped heart. A defibrillator is to store 3.0 J of energy in a 1.2 milli-Farad capacitor. What voltage is required? a) 5000V b) 71V c) 140V d)10^4V e)35V
a) +1.6 x 10-15C.
If 10,000 electrons are removed from a neutral plastic ball, its charge is now: a) +1.6 x 10-15C. b) +1.6 x 10-23C. c) -1.6 x 10-15C. d) -1.6 x 10-23C.
c) 500 V
If a 20 μF capacitor is to have an energy content of 2.5 J, it must be placed across potential difference of: a) 150 V b) 350 V c) 500 V d) 0.25 MV.
a) the rod will attract the conductor
If a charged rod is brought near to a conductor, which has no net charge, what will happen? a) the rod will attract the conductor b) the rod will repel the conductor c) the rod will have no effect on the conductor unless they touch d) it is different every time. there is no way to know unless you try it
e) unchanged
If the charge on parallel plates is doubled, the capacitance will be changed by a factor of: a) one half b) two c) four d) one fourth e) unchanged
b) two
If the distance between two parallel plates is cut in half, the capacitance will be changed by a factor of: a) one half b) two c) four d) one fourth e) unchanged
c) remains the same
If the resistor R2in the previous question is placed in parallel with R1, the power dissipated by R1: a) decreases b) increases c) remains the same d) may be any of the above, depending on the values of R1 and R2
b) negative
If the wrong direction is assumed for a current, in a circuit that is being analyzed by Kirchhoff's rules, the value of the current that is obtained will be: a) positive b) negative c) incorrect d) zero
d) 1.3 μF
In Figure 1 (series), the three capacitors are 3.0μF, 4.0 μF, and 5.0 μF. Please find the single equivalent capacitor, which could replace these three? a) 12 μF b) 6.0μF c) 2.3 μF d) 1.3 μF e) 0.78 μF
b) 23 μC
In Figure 1(series), the capacitors are 3.0 μF, 4.0 μF, and 5.0 μF, respectively. Find the charge on C1(the leftmost capacitor) if the battery voltage is 18 V. a) 14 μC b) 23 μC c) 41 μC d) 54 μC e) 110 μC
b)depends on the medium the charges are located in.
In a formula F = keQ1Q2/r2, the value of the constant ke: a)is the same under all circumstances. b)depends on the medium the charges are located in. c)is different for positive and negative charges. d)has the numerical value 1.6 x 10-19 .
b) 2.4 x 10^6J.
In charging a storage battery, a total of 2.0 x 10^5C is transferred from one set of electrodes to another. The potential difference between the electrodes is 12 V. The energy stored in the battery is: a) 1.7 x 10^4J. b) 2.4 x 10^6J. c) 2.4 x 10^7J. d 2.0x10^7J.
a) conducting solids
In general, which of the following have larger dielectric constants? a) conducting solids b) conducting liquids c) non-conducting solids d) non-conducting liquids e) vacuum
b) 72 μC
In the Figure 2 (parallel), the capacitors are 2.0 μF, 3.0 μF, and 5.0 μF respectively. If the battery voltage is 24 V, find the charge stored on C2(the center capacitor). a) 240 μC b) 72 μC c) 60 μC d) 30 μC e) 15 μC
c) 10 μF
In the Figure 2(parallel), the capacitors are 2.0 μF, 3.0 and 5.0 μF, respectively. Please find the single equivalent capacitor. a) 0.7 μF b) 1.4 μF c) 10 μF d) 0.10 μF e) 5.0 μF
b) field
Of the following quantities, which one is a vector? a) charge b) field c) energy d) potential difference
a) weaker
Relative to the electrical force between two protons, the gravitational force between them is: a) weaker b) equal in magnitude c) stronger d) any of the above, depending on how far apart the protons are
a) uniformly distributed on the sphere's surface
Ten million electrons are placed on a solid copper sphere. The electrons become: a) uniformly distributed on the sphere's surface b) uniformly distributed in the sphere's interior c)concentrated at the center of the sphere d) concentrated at the bottom of the sphere
c) 6.4V
The 8.0-omega coil of a loudspeaker carries a current of 0.80 A. The potential difference across its terminals is: a) 0.1V b) 5.1V c) 6.4V d) 10V
b) 50 V
The capacitor combination in the previous question is connected across a 100-V battery. The potential difference across each capacitor is: a) 25 V b) 50 V c) 100 V d) 200 V
c) 100 V
The capacitor combination in the previous question is connected across a 100-V battery. The potential difference across each capacitor is: a) 25 V b) 50 V c) 100 V d) 200 V
b) farad
The common derived unit which is equivalent to "Coulomb divided by Volt" is the: a) joule b) farad c) henry d) watt e) none of the above
c) 8 omega
Two identical resistors in parallel have an equivalent resistance of 2 omega. If the resistors were in series, what would be their equivalent resistance? a) 2 omega b) 4 omega c) 8 omega d) 16 omega
a)The 60 W has the largest resistance.
Two light bulbs(30 W and60 W) are connected in series with a battery. Which of the following is true? a)The 60 W has the largest resistance. b)The 30 W has the largest resistance c)The 60 W has the largest current. d)The 30 W has the largest current.
a) 20 J
the electric potential energy of a charge q at a point in space is 10J. that charge is removed, and replaced with a charge 2q. what is the potential energy of this new charge? a) 20 J b) 5J c) 10J d) 40J
d) 40J
the electric potential energy of a charge q at a point in space is 20J. that charge is removed, and replaced with a charge 2q. what is the potential energy of this new charge? a) 20 J b) 80J c) 10J d) 40J
c) CV2
the farad is not equivalent to which of the following combination of units? a) C2/J b) C/V c) CV2 d) J/V2
a)contains most of the atom's mass.
the nucleus of an atom: a)contains most of the atom's mass. b)is nearly as large as the atom. c)is electrically neutral. d)All of the above are correct.
b) is a negative number
the potential near a single negative charge with nothing else around it a) is a positive number b) is a negative number c) can be positive or negative number d) is in the positive direction e) is in the negative direction
a) is a positive number
the potential near a single positive charge with nothing else around it a) is a positive number b) is a negative number c) can be positive or negative number d) is in the positive direction e) is in the negative direction
c) top
the region between parallel conducting plates has a uniform electric field pointing in the negative y direction. which side has higher potential? a) left b) right c) top d) bottom
d) bottom
the region between parallel conducting plates has a uniform electric field pointing in the negative y direction. which side has lower potential? a) left b) right c) top d) bottom
a) mass
the resistance of a conductor does not depend on its: a) mass b) length c) cross-sectional area d) resistivity
e) none listed
which resistors are in parallel in the circuit shown to the right? a) R2 and R3 b) R2 and R4 c) R1 and R2 d) R1 and R5 e) none listed
a) R2 and R3
which resistors are in series in the circuit shown to the right? a) R2 and R3 b) R2 and R4 c) R1 and R2 d) R1 and R5 e) none listed
b) P/2
A 10-omega resistor and a 20-omega resistor are connected in parallel to a battery. If heat is produced in the 10-omega resistor at the rate P, the rate at which heat is produced in the 20-omega resistor is: a) P/4 b) P/2 c) P d) 2P
c) 2.7x10-4 J
A 12 V battery is connected to a 3.7 μF capacitor. How much energy is stored in the capacitor? a) 4.4 x 10-5 J b) 2.2x10-5 J c) 2.7x10-4 J d) 3.1x10-7 J e) 6.2 x 10-7 J
b) 2 A
A 12-V potential difference is applied across a parallel combination of four 6-omega resistors. The current in each resistor is: a) 0.5A b) 2 A c) 8 A d) 18 A
a) 0.5 A
A 12-V potential difference is applied across a series combination of four 6-omega resistors. The current in each resistor is: a) 0.5 A b) 2 A c) 8 A d) 18 A
d) 2.2 MJ
A 12V storage battery produces a current of 50 A for one hour. How much energy is used in that hour? a) 50 J b) 0.60 kJ c) 36 kJ d) 2.2 MJ
a) 0.5A
A 20-V potential difference is applied across a series combination of a 10-omega resistor and a 30-omega resistor. What is the current in the 10-omega resistor? a) 0.5A b) 0.67A c) 1A d) 2A
b) 16 V
A 4.0-omega resistor is connected to a 20-V battery with an internal resistance of 1.0omega. The potential difference across the resistor is: a) 4 V b) 16 V c) 19 V d) 20 V
c) 1.1 omega
A 50-V battery is connected across a 10-omega resistor. If the circuit has a current of 4.5 A, what is the internal resistance of the battery? a) zero b) 0.5 omega c) 1.1 omega d) 5 omega
b) 4 x 10-4C
A 50-μF capacitor has a potential difference of 8 V across it. Its charge is: a) 4 x 10-3C b) 4 x 10-4C c) 6.25x10-5C d) 6.25x10-6C.
b) the equivalent resistance of the circuit
A battery is connected to an external circuit. The potential drop within the battery is proportional to: a) the EMF of the battery b) the equivalent resistance of the circuit c) the power dissipated in the circuit d) all of the above
d) 40 μF
A capacitor acquires a charge of 0.002C when connected across a 50-V battery. Its capacitance is: a) 1 μF b) 2 μF c) 4 μF d) 40 μF
e) quadrupled
A capacitor is connected to a battery. If the battery voltage is doubled then the energy stored is: a) cut by a factor of one-fourth b) cut in half c) unchanged d) doubled e) quadrupled
a) 1/4R
A certain wire has a resistance R. What is the resistance of a second wire, identical to the first except for having twice its diameter? a) 1/4R b) 1/2R c) 2R d) 4R
c) increases to twice its former magnitude
A charge of +q is placed 2 cm from a charge of -Q. A second charge of +q is then placed next to the first. The force on the charge of -Q: a) decreases to half its former magnitude b) remains the same c) increases to twice its former magnitude d) increases to four times its former magnitude
c) 10^3V
A charge of 10^-10C between two parallel metal plates, 1 cm apart, experiences a force of 10^-5N. The potential difference between the plates is: a) 10^-5V b) 10V c) 10^3V d)10^5V
d) 2.2
A parallel plate capacitor has capacitance of 50 pF in air and 110 pF when immersed in turpentine. The dielectric constant of turpentine is: a) 0.45 b) 0.55 c) 1.1 d) 2.2
d) 30 μC.
A parallel plate capacitor of 2.5 μF is connected to the terminals of a 12V battery. The charge stored on the plates is: a) 2.5 μC. b) 12 μC. c) 0.21 μC. d) 30 μC. e) 4.8 μC.
c) 3U
A parallel plate capacitor with air between plates is charged until a potential difference V appears across it. Another capacitor, having hard rubber (K= 3) between its plates but otherwise identical, is also charged to the same potential difference. If the energy of the first capacitor is U, that of the second is: a) U/3 b) U c) 3U d) 9U
b) 2.4
A parallel plate capacitor with empty space between the plates has a capacitance of 2.5μF. When a thin sheet of plastic is inserted between the plates it completely fills the space and changes the capacitance to 6.1μF. What is the dielectric constant of this plastic? a) 0.41 b) 2.4 c) 4.2 d) 1.4 e) 6.1
a) decreases
A resistor R1 dissipates the power P when connected to a certain battery. If a resistor R2is inserted in series with R1, the power dissipated by R1: a) decreases b) increases c) remains the same d) may be any of the above, depending on the values of R1 and R2
c) 24 omega
A resistor of unknown resistance is in parallel with a 12-omega resistor. A battery with an EMF of 24V and negligible internal resistance is connected across the combination. The battery provides a current of 3A. What is the unknown resistance? a) 1 omega b) 12 omega c) 24 omega d) 36 omega
e) all of the above are correct
A rod with an unknown charge attracts a plastic ball. One or more of the following might describe them? a) the rod is positive and the ball is negative b) the rod is negative and the ball is positive c) the rod is positive and the ball is uncharged d) the rod is negative and the ball is uncharged e) all of the above are correct f) none of the above are correct
d) 7.35 C/s
A storage battery is being charged at a rate of 100 W at a potential difference of 13.6V. The rate at which charge is being transferred between its plates is: a) 0.136 C/s. b) 0.54 C/s c) 1360 C/s d) 7.35 C/s
c) both charges are positive or both are negative
A system of two charges has a positive potential energy. This signifies that: a) both charges are positive b) both charges are negative c) both charges are positive or both are negative d) one charge is positive and the other is negative
b) 50 mm
An electric field of magnitude 200 V/m can be produce by applying a potential difference of 10 V to a pair of parallel metal plates separated by: a) 20 mm b) 50 mm c) 200 mm d) 2000 m
b) 6 omega
An electric heater draws a current of 20A when connected to a 120V power source. what is its resistance? a) 0.17 omega b) 6 omega c) 8 omega d) 2400 omega
c) the electron has the greater speed
An electron and proton are accelerated through the same potential difference a) the electron has the greater K b) the proton has the greater K c) the electron has the greater speed d) the proton has the greater speed
a) 0.23V
An electron between two metal plates 40 mm apart experiences an acceleration of 1.0 x 10^12m/s2. The potential difference between the plates is: a) 0.23V b) 5.7V c) 0.14 kV d) 2.8x10^12V
a) 7.3 x 10^6m/s.
An electron whose KE is 150 eV has a speed of: a) 7.3 x 10^6m/s. b) 5.1 x 10^6m/s. c) 2.3x10^8m/s d) 7.3 x 10^13m/s
b) 0.28 keV
An electron whose speed is 1.0 x 107m/s has a KE of: a) 4.6 x 10^-17eV. b) 0.28 keV c) 0.73 keV d) 7.3x10^13 keV
d) 4.0 x 105N/C
The electric field 20 mm from a certain charge has a magnitude of 1.0 x 105N/C. The magnitude of the electric field 10 mm from the charge is: a) 2.5 x 104N/C b) 5.0 x 104N/C c) 2.0 x 105N/C d) 4.0 x 105N/C
c) the force a charge of one coulomb would experience there.
The electric field at a point in space is equal in magnitude to: a) the number of electric field lines that pass through the point. b) the electric charge there. c) the force a charge of one coulomb would experience there. d) the force an electron would experience there
d) energy
The electron volt is a unit of: a) charge b) potential difference c) momentum d) energy
b) are at specific distances away from the nucleus
The electrons in an atom a) are bound to it permanently b) are at specific distances away from the nucleus c) have more mass than the nucleus d) may be positively or negatively charged
d) electric field
The energy content of a charged capacitor resides in its: a) plates b) potential difference c) charge d) electric field
b) 7.5 omega
The equivalent resistance of a 10-omega resistor and a 30-omega resistor connected in parallel is: a) 0.13 omega b) 7.5 omega c) 20 omega d) 40 omega
b) 1.5 omega
The equivalent resistance of three 2-omega resistors in a circuit cannot be: a) 0.67 omega b) 1.5 omega c) 3 omega d) 6 omega
d) 3.2 x 10-5N
The force between two charges of -3.0 x 10-9C that are 50 mm apart is a) 1.8 x 10-16N b) 3.6 x 10-15N c) 1.6 x 10-6N d) 3.2 x 10-5N
b) 1.3 x 10-10C
The magnitude of the charges in the previous question is: a) 6.7x10-11C b) 1.3 x 10-10C c) 1.1 x 10-9C d) 2.1 x 10-9C
b) uniform throughout the region
The magnitude of the electric field in the region between two parallel oppositely charged metal plates is: a) zero b) uniform throughout the region c) greatest near the positive plate d) greatest near the negative plate
c) 3.2 x 10-17N
The magnitude of the force on an electron in an electric field of 200 N/C is: a) 8.0 x 10-22N b) 3.2 x 10-21N c) 3.2 x 10-17N d) 6.4 x 10-15N
d) 4C
The plate area of a parallel-plate capacitor of capacitance C is doubled and the distance between the plates is halved, so that the volume of the dielectric remains the same. The capacitance of the capacitor is: a) C/4 b) C c) 2C d) 4C
b) 0.37 kW
The power rating of an electric motor that draws a current of 3.00 A when operated at 120V is: a) 40W b) 0.37 kW c) 0.54 kW d) 1.08 kW
a) V/m
The units for electric field are N/C. Which of the following are also units for electric field? a) V/m b) V/m2 c) Vm d) Vm2
c) 100 μF
Two 50 μF capacitors are connected in parallel. The equivalent capacitance of the combination is: a)25 μF b) 50 μF c) 100 μF d) 200 μF.
a) 25 μF
Two 50 μF capacitors are connected in series. The equivalent capacitance of the combination is: a) 25 μF b) 50 μF c) 100 μF d) 200 μF.
c) the same
Two charges of +Q are 1 cm apart. If one of the charges is replaced by a charge of -Q, the magnitude of the force between them is: a) zero b) smaller c) the same d) larger
d) 2.5x10-5N
Two charges repel each other with a force of 10-6N when they are 10 cm apart. When they are brought closer together until they are 2 cm apart, the force between them becomes: a) 4 x 10-8N b) 5 x 10-6N c) 8 x 10-6N d) 2.5x10-5N
c) 9
Two charges, one positive and the other negative, are initially 2 cm apart and are then pulled away from each other until they are 6 cm apart. The force between them is now smaller by a factor of: a) √3 b) 3 c) 9 d) 27
c) 4 mm
Two equal charges attract each other with a force of 1.0 x 10-5N. When they are moved 4 mm farther apart, the force between them becomes 2.5 x 10-6N. The original separation of the charges was a) 1 mm b) 2 mm c) 4 mm d) 8 mm
c) some valence electrons move to the interior of the conductor
What happens to the charges inside the conductor of the previous question? (when conductor has electrons removed) a) the valence electrons that are left spread out evenly b) the excess protons move to the surface c) some valence electrons move to the interior of the conductor d) all of the electrons move to the surface
a) 5V
What is the potential difference across the 10-omega resistor in the previous question? a) 5V b) 10V c) 15V d) 20V
b) it becomes positively charged
When a conductor, which is originally neutral, has a significant number of electrons removed, what happens to the charge on the conductor? a) it becomes negatively charged b) it becomes positively charged c) it remains unchanged d) all of the above are correct
a) decreases
When a slab of insulating material is placed between the plates of a charged capacitor, how does the electric field change? a) decreases b) increases c) stays the same d) any of the above, depending on the circumstance
c) 1/2L and 2A
Which of the following combinations of length and cross-sectional area will give a certain volume of copper the least resistance? a) L and A b) 2L and 1/2A c) 1/2L and 2A d) does not matter, because the volume of copper remains the same
b)The electron and proton have approximately the same mass.
Which one or more of the following statements is NOT true? a)The electron and proton have charges of the same magnitude but of opposite sign. b)The electron and proton have approximately the same mass. c)The proton and neutron have approximately the same mass. d)Atomic nuclei contain only protons and neutrons.
d) 2P
a 10-omega resistor and a 20-omega resistor are connected in series to a battery. If heat is produced in the 10-omega resistor at the rate P, the rate at which heat is produced in the 20-omega resistor is: a) P/4 b) P/2 c) P d) 2P
c) 2A
a 20-V potential difference is applied across the resistors in the previous question. What is the current in the 10-omega resistor? a) 0.5A b) 1A c) 2A d) 2.67A
a) zero
a charge of 2C is moved 3m along an equipotential line where the potential is 6V. what is the change in PE of the charge? a) zero b) 6J c) 36J d) 1J e) 12J
e) zero
a charge of 3C is moved 2m along an equipotential line where the potential is 6V. what is the change in PE of the charge? a) 12J b) 6J c) 36J d) 18J e) zero
f) 12A into the junction
a junction has 3 wires leading to it. on one wire, the current out of the junction is 10A. a second wire has 2A leading away from the junction. what is the current in the third wire? a) 8A out of the junction b) 8A into the junction c) 10A out of the junction d) 10A into the junction e) 12A out of the junction f) 12A into the junction
b) 8A into the junction
a junction has 3 wires leading to it. on one wire, the current out of the junction is 10A. a second wire has 2A leading into the junction. what is the current in the third wire? a) 8A out of the junction b) 8A into the junction c) 10A out of the junction d) 10A into the junction e) 12A out of the junction f) 12A into the junction
d) down; decreasing
a proton is released midway between two plates and is allowed to move freely (nothing is affecting it besides the electric field). which way does it go, and what is happening to its potential energy)? a) up; increasing b) up; decreasing c) down; increasing d) down; decreasing
b) 2R
a resistor has a resistance R. if the length of a resistor is doubled, the resistance is a) R b) 2R c) 1/2R d) 4R e) 1/4R
c) 1/2R
a resistor has a resistance R. if the length of a resistor is halved, the resistance is a) R b) 2R c) 1/2R d) 4R e) 1/4R
b) it increases
a resistor in a circuit has a current through it, causing the resistor to heat up. what happens to the current through the resistor as it gets hotter? a) it stays the same b) it increases c) it decreases d) need to know exact temperatures
b) up; decreasing
an electron is released midway between two plates and is allowed to move freely (nothing is affecting it besides the electric field). which way does it go, and what is happening to its potential energy)? a) up; increasing b) up; decreasing c) down; increasing d) down; decreasing
b) it has a deficiency of electrons
an object has a positive electric charge whenever: a) it has an excess of electrons b) it has a deficiency of electrons c) the nuclei of its atoms are positively charged d) the electrons of its atoms are positively charged
a) R1
assume R1 is the smallest resistor, consecutively up to R5 being the biggest resistor. which of the following resistors has the largest current through it? a) R1 b) R2 c) R4
c) R4
assume R1 is the smallest resistor, consecutively up to R5 being the biggest resistor. which of the following resistors has the smallest current through it? a) R1 b) R2 c) R4
c)is a quantity that cannot be subdivided into parcels smaller than 1.6 x 10-19C.
electric charge: a)is a quantity that can be subdivided into indefinitely small values. b)is a continuous quantity that can have any value. c)is a quantity that cannot be subdivided into parcels smaller than 1.6 x 10-19C. d)occurs only in separate parcels, each of 1C.
c) have the same pattern around a metal sphere as they do around a point charge
electric field lines: a) leave negative charges and enter positive ones b) are close together where E is weak and far apart when E is strong c) have the same pattern around a metal sphere as they do around a point charge d) physically exist
d) Omega2/V
of the following combinations of units, which one is not equal to the watt? a) J/s b) AV c) A2Omega d) Omega2/V e) Two of the above are not equivalent to watt
d) none of the above
resistivity depends on which of the following? a) mass b) length c)cross-sectional area d) none of the above
