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Physic
Q:
At one instant an electron (charge = "1.6 ï‚´10"19C) is moving in the xyplane, the components of its velocity being vx= 5.0 ï‚´105m/s and vy= 3.0 ï‚´105m/s. A magnetic field of 0.80 T is in the positive ydirection. At that instant the magnitude of the magnetic force on the electron is:
A) 0 N
B) 3.8 ï‚´10"14N
C) 6.4 ï‚´10"14N
D) 7.5 ï‚´10"14N
E) 1.0 ï‚´10"13N
Q:
At one instant an electron (charge = -1.6 x10-19C) is moving in the xyplane, the components of its velocity being vx= 5.0 x105m/s and vy= 3.0 x105m/s. A magnetic field of 0.80 T is in the positive xdirection. At that instant the magnitude of the magnetic force on the electron is:A) 0 NB) 3.8 x10-14NC) 6.0 x10-14ND) 6.4x10-14NE) 1.0 x10-13N
Q:
An electron (charge = -1.6 x10-19C) is moving at 3.0 x105m/s in the positive xdirection. A magnetic field of 0.80 T is in the positive zdirection. The magnetic force on the electron is:A) 0 NB) 4.5x10-14N in the positive zdirectionC) 4.5 x10-14N in the negative zdirectionD) 4.5 x10-14N in the positive ydirectionE) 4.5 x10-14N in the negative ydirection
Q:
An electron moves in the negative xdirection, through a uniform magnetic field that is in the negative ydirection. The magnetic force on the electron is: A) in the negative xdirection
B) in the positive ydirection
C) in the negative ydirection
D) in the positive zdirection
E) in the negative zdirection
Q:
A beam of electrons is sent horizontally down the axis of a tube to strike a fluorescent screen at the end of the tube. On the way, the electrons encounter a magnetic field directed vertically downward. The spot on the screen will therefore be deflected:
A) upward
B) downward
C) to the right as seen from the electron source
D) to the left as seen from the electron source
E) not at all
Q:
A hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north. It will be deflected:
A) up
B) down
C) north
D) south
E) not at all
Q:
An electron and a proton are both initially moving with the same speed and in the same direction at 90Ëš to the same uniform magnetic field. They experience magnetic forces, which are initially:
A) identical
B) equal in magnitude but opposite in direction
C) in the same direction and differing in magnitude by a factor of 1840
D) in opposite directions and differing in magnitude by a factor of 1840
E) equal in magnitude but perpendicular to each other
Q:
An electron travels due north through a vacuum in a region of uniform magnetic field that is also directed due north. It will:
A) be unaffected by the field
B) speed up
C) slow down
D) follow a right-handed corkscrew path
E) follow a left-handed corkscrew path
Q:
A proton (charge e), traveling perpendicular to a magnetic field, experiences the same force as an alpha particle (charge 2e) which is also traveling perpendicular to the same field. The ratio of their speeds, vproton/valphais:
A) 0.5
B) 1
C) 2
D) 4
E) 8
Q:
A magnetic field exerts a force on a charged particle:
A) always
B) never
C) if the particle is moving across the field lines
D) if the particle is moving along the field lines
E) if the particle is at rest
Q:
An electron is moving north in a region where the magnetic field is south. The magnetic force exerted on the electron is:
A) zero
B) up
C) north
D) south
E) west
Q:
The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials. The field direction is:
A) one of the directions of the velocity when the magnetic force is zero
B) the direction of the velocity when the magnetic force is a maximum
C) the direction of the magnetic force
D) perpendicular to the velocity when the magnetic force is zero
E) none of the above
Q:
Units of a magnetic field might be:A) C.m/sB) C.s/mC) C/kgD) kg/C.sE) N/C.m
Q:
A galvanometer has an internal resistance of 12 and requires 0.01 A for full scale deflection. To convert it to a voltmeter reading 3 V full scale, one must use a series resistance of:A) 102 B) 288 C) 300 D) 360 E) 412
Q:
A certain ammeter has an internal resistance of 1 and a range from 0 to 50 mA. To make its range from 0 to 5 A, use:A) a series resistance of 99 B) an extremely large (say 106) series resistanceC) a resistance of 99 in parallelD) a resistance of 1/99 in parallelE) a resistance of 1/1000in parallel
Q:
A certain voltmeter has an internal resistance of 10,000 and a range from 0 to 100 V. To give it a range from 0 to 1000 V, one should connect:A) 100,000 in seriesB) 100,000 in parallelC) 1000 in seriesD) 1000 in parallelE) 90,000 in series
Q:
To make a galvanometer into an ammeter, connect:
A) a high resistance in parallel
B) a high resistance in series
C) a low resistance in series
D) a low resistance in parallel
E) a source of emf in series
Q:
In the figure, voltmeter V1reads 600 V, voltmeter V2reads 580 V, and ammeter A reads 100 A. The power wasted in the transmission line connecting the power house to the consumer is: A) 1 kW
B) 2 kW
C) 58 kW
D) 59 kW
E) 60 kW
Q:
A certain galvanometer has a resistance of 100 and requires 1 mA for full scale deflection. To make this into a voltmeter reading 1 V full scale, connect a resistance of:A) 1000 in parallelB) 900 in seriesC) 1000 in seriesD) 10 in parallelE) 0.1 in series
Q:
When switch S is open, the ammeter in the circuit shown reads 2.0 A. When S is closed, the ammeter reading:A) increases slightlyB) remains the sameC) decreases slightlyD) doublesE) halves
Q:
The circuit shown was wired for the purpose of measuring the resistance of the lamp L. Inspection shows that: A) voltmeter V and rheostat R should be interchanged
B) the circuit is satisfactory
C) the ammeter A should be in parallel with R, not L
D) the meters, V and A, should be interchanged
E) L and V should be interchanged
Q:
Two identical batteries, each with an emf of 18 V and an internal resistance of 1 , are wired in parallel by connecting their positive terminals together and connecting their negative terminals together. The combination is then wired across a 4-resistor. The potential difference across the 4-resistor is:A) 4.0 VB) 8.0 VC) 14 VD) 16 VE) 29 V
Q:
Two identical batteries, each with an emf of 18 V and an internal resistance of 1 , are wired in parallel by connecting their positive terminals together and connecting their negative terminals together. The combination is then wired across a 4-resistor. The current in each battery is:A) 1.0 AB) 2.0 AC) 3.6 AD) 4.0 AE) 4.5 A
Q:
If a circuit has Lclosed loops, Bbranches, and Jjunctions the number of independent loop equations is:A) B- J+ 1B) B- JC) BD) LE) L- J
Q:
For any circuit the number of independent equations containing emf's, resistances, and currents equals:
A) the number of junctions
B) the number of junctions minus 1
C) the number of branches
D) the number of branches minus 1
E) the number of closed loops
Q:
A 3-and a 1.5-resistor are wired in parallel and the combination is wired in series to a 4-resistor and a 10-V emf device. The potential difference across the 3-resistor is:A) 2.0 VB) 6.0 VC) 8.0 VD) 10 VE) 12 V
Q:
A 3-and a 1.5-resistor are wired in parallel and the combination is wired in series to a 4-resistor and a 10-V emf device. The current in the 3-resistor is:A) 0.33 AB) 0.67 AC) 2.0 AD) 3.3 AE) 6.7 A
Q:
In the diagrams, all light bulbs are identical and all emf devices are identical. In which circuit (I, II, III, IV, V) will the bulbs be dimmest? A) I
B) II
C) III
D) IV
E) V
Q:
In the diagrams, all light bulbs are identical and all emf devices are identical. In which circuit (I, II, III, IV, V) will the bulbs glow with the same brightness as in circuit X? A) I
B) II
C) III
D) IV
E) V
Q:
The current in the 5.0-ï—resistor in the circuit shown is: A) 0.42 A
B) 0.67 A
C) 1.5 A
D) 2.4 A
E) 3.0 A
Q:
Each of the resistors in the diagram is 12 . The resistance of the entire circuit is:A) 5.8B) 25 C) 48D) 120 E) none of these
Q:
The equivalent resistance between points 1 and 2 of the circuit shown is:A) 2.5 B) 4.0C) 5.0D) 6.5E) 16
Q:
Resistor 1 has twice the resistance of resistor 2. They are connected in parallel to a battery. The ratio of the thermal energy dissipation by 1 to that by 2 is:
A) 1:4
B) 1:2
C) 1:1
D) 2:1
E) 4:1
Q:
Resistor 1 has twice the resistance of resistor 2. The two are connected in parallel and a potential difference is maintained across the combination. The rate of thermal energy dissipation in 1 is:
A) the same as that in 2
B) twice that in 2
C) half that in 2
D) four times that in 2
E) one fourth that in 2
Q:
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 are true
Q:
Two wires made of the same material have the same length but different diameter. They are connected in parallel to a battery. The quantity that is NOT the same for the wires is:
A) the end-to-end potential difference
B) the current
C) the current density
D) the electric field
E) the electron drift velocity
Q:
Four 20-resistors are connected in parallel and the combination is connected to a 20-V emf device. The current in any one of the resistors is:A) 0.25 AB) 1.0 AC) 4.0 AD) 5.0 AE) 100 A
Q:
A battery is connected across a parallel combination of two identical resistors. If the potential difference across the terminals is Vand the current in the battery is i, then:
A) the potential difference across each resistor is Vand the current in each resistor is i
B) the potential difference across each resistor is V/2 and the current in each resistor is i/2
C) the potential difference across each resistor is Vand the current in each resistor is i/2
D) the potential difference across each resistor is V/2 and the current in each resistor is i
E) none of the above are true
Q:
In an antique automobile, a 6-V battery supplies a total of 48 W to two identical headlights in parallel. The resistance of each bulb is:A) 0.75 B) 1.5 C) 3 D) 4 E) 8
Q:
By using only two resistors, R1and R2a student is able to obtain resistances of 3 , 4 , 12 , and 16 . The values of R1and R2are:A) 3, 4 B) 2, 12 C) 3, 16 D) 4, 12 E) 4, 16
Q:
A total resistance of 3.0 is to be produced by combining an unknown resistor Rwith a 12 resistor. What is the value of Rand how is it to be connected to the 12 resistor?A) 2.4, parallelB) 2.4, seriesC) 4.0, parallelD) 4.0, seriesE) 9.0 , series
Q:
Four 20-resistors are connected in parallel and the combination is connected to a 20-V emf device. The current in the device is:A) 0.25 AB) 1.0 AC) 4.0 AD) 5.0 AE) 100 A
Q:
A resistor with resistance R1and a resistor with resistance R2are connected in parallel to an ideal battery with emf . The rate of thermal energy generation in the resistor with resistance R1is:
A) 2/R1
B) 2 R1/(R1+ R2)2
C) 2 /(R1+ R2)
D) 2/R2
E)
Q:
A 120-V power line is protected by a 15-A fuse. What is the maximum number of 120 V, 500 W light bulbs that can be operated at full brightness from this line?
A) 1
B) 2
C) 3
D) 4
E) 5
Q:
Four wires meet at a junction. The first carries 4A into the junction, the second carries 5A out of the junction, and the third carries 2A out of the junction. The fourth carries:
A) 7A out of the junction
B) 7A into the junction
C) 3A out of the junction
D) 3A into the junction
E) 1A into the junction
Q:
A portion of a circuit is shown, with the values of the currents given for some branches. What is the direction and value of the current i? A) , 6A
B) ï‚, 6A
C) , 4A
D) ï‚, 4A
E) , 2A
Q:
In the context of the loop and junctions rules for electrical circuits a junction is:
A) where a wire is connected to a resistor
B) where a wire is connected to a battery
C) where only two wires are joined
D) where three or more wires are joined
E) where a wire is bent
Q:
"The sum of the currents into a junction equals the sum of the currents out of the junction" is a consequence of:
A) Newton's third law
B) Ohm's law
C) Newton's second law
D) conservation of energy
E) conservation of charge
Q:
The positive terminals of two batteries with emf's of 1 and 2, respectively, are connected together. Here 1 >2.The circuit is completed by connecting the negative terminals. If each battery has an internal resistance of r, the rate in watts at which electrical energy is converted to chemical energy in the smaller battery is:A) /rB) /2rC) (2- 1)1/rD) (2- 1)1/2rE) /2r
Q:
A battery of emf 24 V is connected to a 6.0-resistor. As a result, current of 3.0 A exists in the resistor. The rate at which energy is being dissipated in the battery is:A) 3.0 WB) 6.0 WC) 18 WD) 54 WE) 72 W
Q:
Resistances of 2.0 , 4.0 , and 6.0 and a 24-V emf device are all in series. The circuit is initially ungrounded. After grounding, the current in the circuit:A) increasesB) decreasesC) does not changeD) depends on where in the circuit the ground wire is attachedE) depends on what the circuit is grounded to
Q:
A battery of emf 24 V is connected to a 6-resistor. As a result, current of 3 A exists in the resistor. The terminal potential difference of the battery is:A) 0 VB) 6 VC) 12 VD) 18 VE) 24 V
Q:
A battery has an emf of 9V and an internal resistance of 2. If the potential difference across its terminals is greater than 9V:A) it must be connected across a large external resistanceB) it must be connected across a small external resistanceC) the current must be out of the positive terminalD) the current must be out of the negative terminalE) the current must be zero
Q:
The terminal potential difference of a battery is less than its emf:
A) under all conditions
B) only when the battery is being charged
C) only when the battery is being discharged
D) only when there is no current in the battery
E) under no conditions
Q:
The emf of a battery is equal to its terminal potential difference:
A) under all conditions
B) only when the battery is being charged
C) only when a large current is in the battery
D) only when there is no current in the battery
E) under no conditions
Q:
Resistances of 2.0 , 4.0 , and 6.0 and a 24-V emf device are all in series. The potential difference across the 2.0-resistor is:A) 4 VB) 8 VC) 12 VD) 24 VE) 48 V
Q:
Resistor 1 has twice the resistance of resistor 2. The two are connected in series and a potential difference is maintained across the combination. The rate of thermal energy dissipation in 1 is:
A) the same as that in 2
B) twice that in 2
C) half that in 2
D) four times that in 2
E) one fourth that in 2
Q:
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 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 are true
Q:
A battery is connected across a series combination of two identical resistors. If the potential difference across the terminals is Vand the current in the battery is i, then:
A) the potential difference across each resistor is Vand the current in each resistor is i
B) the potential difference across each resistor is V/2 and the current in each resistor is i/2
C) the potential difference across each resistor is Vand the current in each resistor is i/2
D) the potential difference across each resistor is V/2 and the current in each resistor is i
E) none of the above are true
Q:
In the diagram, the current in the 3-resistor is 4 A. The potential difference between points 1 and 2 is:A) 0.75 VB) 0.8 VC) 1.25 VD) 12 VE) 20 V
Q:
Four 20-resistors are connected in series and the combination is connected to a 20-V emf device. The potential difference across any one of the resistors is:A) 1 VB) 4 VC) 5 VD) 20 VE) 80 V
Q:
Resistances of 2.0 , 4.0 and 6.0 and a 24-V battery are all in series. The current in the 2.0 resistor is:A) 12 AB) 4.0 AC) 2.4 AD) 2.0 AE) 0.50 A
Q:
Nine identical wires, each of diameter dand length L, are connected in series. The combination has the same resistance as a single similar wire of length Lbut whose diameter is:
A) 9d
B) 3d
C) d/3
D) d/9
E) d/81
Q:
Four 20-resistors are connected in series and the combination is connected to a 20-V emf device. The current in any one of the resistors is:A) 0.25 AB) 1.0 AC) 4.0 AD) 5.0 AE) 100 A
Q:
Two wires are made of the same material and have the same length but different radii. They are joined end-to-end and a potential difference is maintained across the combination. Of the following the quantity that is the same for both wires is:
A) potential difference
B) current
C) current density
D) electric field
E) conduction electron drift speed
Q:
Two wires made of the same material have the same length but different diameters. They are connected in series to a battery. The quantity that is the same for the wires is:
A) the end-to-end potential difference
B) the current
C) the current density
D) the electric field
E) the electron drift velocity
Q:
A series circuit consists of a battery with internal resistance rand an external resistor R. If these two resistances are equal (r= R) then the energy dissipated per unit time by the internal resistance ris:
A) the same as by R
B) half that by R
C) twice that by R
D) one third that by R
E) unknown unless the emf is given
Q:
Two 110-V light bulbs, one labeled 25 W and the other 100 W, are connected in series to a 110 V source. Then:
A) the current in the 100-W bulb is greater than that in the 25-W bulb
B) the current in the 100-W bulb is less than that in the 25-W bulb
C) both bulbs will light with equal brightness
D) each bulb will have a potential difference of 55 V
E) none of the above
Q:
In the diagram R1>R2>R3. Rank the three resistors according to the current in them, least to greatest. A) 1, 2, 3
B) 3, 2, 1
C) 1, 3, 2
D) 3, 1, 2
E) All are the same
Q:
A battery with an emf of 12 V and an internal resistance of 1 is used to charge a battery with an emf of 10 V and an internal resistance of 1 . The current in the circuit is:A) 1 AB) 2 AC) 4 AD) 11 AE) 22 A
Q:
An ideal battery has an emf of 12V. If it is connected to a circuit and creates a current of 4.0 A, what is the power?
A) 0.3 W
B) 3.0 W
C) 36 W
D) 48 W
E) cannot tell without knowing the resistance of the circuit
Q:
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
Q:
"The sum of the emf's and potential differences around a closed loop equals zero" is a consequence of:
A) Newton's third law
B) Ohm's law
C) Newton's second law
D) conservation of energy
E) conservation of charge
Q:
An initially uncharged capacitor C is connected in series with resistor R. This combination is then connected to a battery of emf V0. Sufficient time elapses so that a steady state is reached. Which of the following statements is NOT true?
A) The time constant is independent of V0
B) The final charge on C is independent of R
C) The total energy dissipated by R is independent of R
D) The total energy dissipated by R is independent of V0
E) The initial current (just after the battery was connected) is independent of C
Q:
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 capacitance is about:
Q:
In the circuit shown, both resistors have the same value R. Suppose switch S is initially closed and capacitor C is charged. When switch S is then opened, the circuit has a time constant . Conversely, suppose S is initially open and capacitor C is uncharged. When switch S is then closed, the circuit has a time constant . The ratio ´is:A) 0.5B) 0.67C) 1D) 1.5E) 2
Q:
Four circuits have the form shown in the diagram. The capacitor is initially uncharged and the switch S is open.The values of the emf , resistance R, and the capacitance Cfor each of the circuits areRank the circuits according to the time after switch S is closed for the capacitors to reach half their final charges, least to greatest.A) 1, 2, 3, 4B) 2, 4, 3, 1C) 1, 3, 4, 2D) 4, 2, 1, 3E) 3, 1, 2, 4
Q:
In the circuit shown, the capacitor is initially uncharged, and V= 10 V. At time t= 0, switch S is closed. If denotes the time constant, the approximate current through the 3 resistor when is:A) 0.50 AB) 0.75 AC) 1.0 AD) 1.5 AE) 3.0 A
Q:
Four circuits have the form shown in the diagram. The capacitor is initially uncharged and the switch S is open.The values of the emf , resistance and R, and capacitance C for each for the circuits areRank the circuits according to the current just after switch S is closed least to greatest.A) 1, 2, 3, 4B) 4, 3, 2, 1C) 4, 2, 3, 1D) 4, 2, 1, 3E) 3, 1, 2, 4
Q:
A charged capacitor is being discharged through a resistor. At the end of one time constant the charge has been reduced by (1 - 1/e) = 63% of its initial value. At the end of two time constants the charge has been reduced by what percent of its initial value?A) 82%B) 86%C) 100%D) between 90% and 100%E) need to know more data to answer the question