Final
A particle (mass = 2.0 mg, charge = -6.0 mC) moves in the positive direction along the x axis with a velocity of 3.0 km/s. It enters a magnetic field of (2.0i + 3.0j+ 4.0k) mT. What is the acceleration of the particle?
1) (36j - 27k) m/s^2
An electron follows a circular path (radius = 15 cm) in a uniform magnetic field (magnitude = 3.0 G). What is the period of this motion?
1) 0.12 microseconds
Capacitive reactance XC is given by
1) 1/ᗯC
A 60-Hz ac generator with a peak voltage of 110 V drives a series RC circuit with R = 10.0 W and C = 300 mF. The power factor, cos f, is
3) +0.749.
A 2.0-C charge moves with a velocity of (2.0i + 4.0j + 6.0k) m/s and experiences a magnetic force of (4.0i - 20j + 12k) N. The x component of the magnetic field is equal to zero. Determine the z component of the magnetic field.
3) +5.0 T
A transformer is to be designed to increase the 30 kV-rms output of a generator to the transmission-line voltage of 345 kV-rms. If the primary winding has 80 turns, how many turns must the secondary have?
3) 920
In a parallel RLC circuit, where IR = IR, max sin(wt), the current through the inductor, IL, is
3) IL = -IL, max cos(wt).
An electric heater draws an average power of 1100 Watts when plugged into a 110 V-rms outlet. Calculate the resistance of the heater and the rms current.
1) 11 ohm, 10 A (rms)
A certain brand of hot dog cooker applies a potential difference (120 V) to opposite ends of the hot dog and cooks by means of the joule heat produced. If 60 kJ is needed to cook each hot dog, what current is needed to cook four hot dogs simultaneously in 3.0 min?
1) 11A
The primary winding of an electric train transformer has 400 turns and the secondary has 50. If the input voltage is 120V(rms) what is the output voltage?
1) 15 V (rms)
A series RLC circuit has an impedance of 120W and a resistance of 64W. What average power is delivered to this circuit when Vrms = 90 volts?
1) 36 w
At what frequency will a 12-mF capacitor have a reactance XC = 300W?
1) 44 Hz
A charged particle (m = 5.0 g, q = -70 mC) moves horizontally at a constant speed of 30 km/s in a region where the free fall gravitational acceleration is 9.8 m/s2 downward, the electric field is 700 N/C upward, and the magnetic field is perpendicular to the velocity of the particle. What is the magnitude of the magnetic field in this region?
1) 47 mT
A charged particle moves in a region of uniform magnetic field along a helical path (radius = 5.0 cm, pitch = 12 cm, period = 5.0 ms). What is the speed of this particle as it moves along this path?
1) 67 m/s
When a 20-V emf is placed across two resistors in series, a current of 2.0 A is present in each of the resistors. When the same emf is placed across the same two resistors in parallel, the current through the emf is 10 A. What is the magnitude of the greater of the two resistances
1) 7.2 ohms
A 60-Hz ac generator with a peak voltage of 110 V drives a series RC circuit with R = 10.0 W and C = 300 mF. The peak current in the circuit is
1) 8.24 A
What is the radius of curvature of the path of a 3.0-keV proton in a perpendicular magnetic field of magnitude 0.80 T?
1) 9.9 mm
A positively charged particle has a velocity in the negative z direction at point P. The magnetic force on the particle at this point is in the negative y direction. Which one of the following statements about the magnetic field at point P can be determined from this data?
1) B_X is positive
Inductive reactance XL is given by
1) Lᗯ
A straight wire carries a current of 40 A in a uniform magnetic field (magnitude = 80 mT). If the force per unit length on this wire is 2.0 N/m, determine the angle between the wire and the magnetic field.
1) either 39 or 141 degrees
An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx = 0, what is the direction of the magnetic field?
1) negative y direction
The algebraic sum of the changes of potential around any closed circuit loop is
1) zero.
When a capacitor is fully charged, the current through the capacitor is
1)zero
A 2.0-m wire carries a current of 15 A directed along the positive x axis in a region where the magnetic field is uniform and given by B = (30i - 40j) mT. What is the resulting magnetic force on the wire?
2) (-1.2 k) N
A 2.0-C charge moves with a velocity of (2.0i + 4.0j + 6.0k) m/s and experiences a magnetic force of (4.0i - 20j + 12k) N. The x component of the magnetic field is equal to zero. Determine the y component of the magnetic field.
2) +3.0 T
A 10-mF capacitor is plugged into a 110 V-rms 60-Hz voltage source, with an ammeter in series. What is the rms value of the current through the capacitor?
2) 0.415 A (rms)
A physicist claims that she has found a new particle with a mass 200,000 times the mass of the proton (1.67 ´ 10-27 kg) and a charge of 3.20 ´ 10-19 C. If she is correct, such a particle traveling in a circle in a uniform 5.00 T magnetic field at a velocity of 2500 m/s will have a radius of
2) 0.522 m
What is the kinetic energy of an electron that passes undeviated through perpendicular electric and magnetic fields if E = 4.0 kV/m and B = 8.0 mT?
2) 0.71 eV
Find the resonant frequency for a series RLC circuit where R = 10W, C = 5 mF, and L = 2 mH.
2) 1.592 kHz
A 60-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 W and L = 10.0 mH. The peak current in the circuit is
2) 10.3 A.
A proton is accelerated from rest through a potential difference of 2.5 kV and then moves perpendicularly through a uniform 0.60-T magnetic field. What is the radius of the resulting path?
2) 12 mm
A step-up transformer has an input voltage of 110V(rms). There are 100 turns on the primary and 1500 on the secondary. What is the output voltage?
2) 1650 V (rms)
A straight 10-cm wire bent at its midpoint so as to form an angle of 90° carries a current of 10 A. It lies in the xy plane in a region where the magnetic field is in the positive z direction and has a constant magnitude of 3.0 mT. What is the magnitude of the magnetic force on this wire?
2) 2.1 mN
What is the average power dissipation in a series RC circuit if R = 5 kW, C = 2 mF, and V = 170 cos (300t)?
2) 2.60 W
A straight wire of length 70 cm carries a current of 50 A and makes an angle of 60° with a uniform magnetic field. If the force on the wire is 1.0 N what is the magnitude of B?
2) 33 mT
The inductance of a tuning circuit of an AM radio is 4 mH. Find the capacitance of the circuit required for reception at 1200 kHz.
2) 4.4 pF
A charged particle (mass = 4.0 mg, charge = 5.0 mC) moves in a region where the only force on it is magnetic. What is the magnitude of the acceleration of the particle at a point where the speed of the particle is 5.0 km/s, the magnitude of the magnetic field is 8.0 mT, and the angle between the direction of the magnetic field and the velocity of the particle is 60°?
2) 43 km/s^s
A current I = 3 sin (400 t) amperes flows in a series RL circuit in which L = 1 mH and R = 100W. What is the average power loss?
2) 450 W
An RLC series circuit has R = 100 ohms, C = 25 mF, and L = 0.16 H. For what angular frequency of an ac voltage is the current flow maximum?
2) 500 rad/s
Charlotte says that you can use a voltmeter to find the current direction in a wire if you can't see the terminals it is connected to. Bonnie says that an ammeter will do. Finally, Rita says that you can bring the north pole of a magnet up to the wire and determine the current direction from the direction of the magnetic force on the wire. Which one(s), if any, is(are) correct?
2) Charlotte and Rita are correct, but Bonnie is wrong.
Bert says that a charged particle in a vacuum can travel in a helix only if a uniform electric field and a uniform magnetic field are both present and both parallel to the axis of the helix. Stuart says that only a magnetic field with a component parallel to the axis of the helix is needed. Which one, if either, is correct, and why?
2) Stuart, because a component of velocity in the vertical direction is not changed by a vertical component of a magnetic field.
An explorer walks into a lab in a science building. She has a compass in her hand and finds that the south pole of her compass points toward the room's East wall when she is nearer that wall and toward the west wall when she is nearer that wall. You could explain this if magnetized metal had been installed in the East and West walls with North poles pointing into the room. If no magnetic material was installed in the North or South walls of the room, she would expect that
2) the north pole of the compass would tend to point toward those walls.
In an RC circuit, what fraction of the final energy is stored in an initially uncharged capacitor after it has been charging for 3.0 time constants?
2)0.90
A capacitor in a single-loop RC circuit is charged to 85% of its final potential difference in 2.4 s. What is the time constant for this circuit?
2)1.3s
A particle (mass = 6.0 mg) moves with a speed of 4.0 km/s in a direction that makes an angle of 37° above the positive x axis in the xy plane. At the instant it enters a magnetic field of (5.0i) mT it experiences an acceleration of (8.0k) m/s2. What is the charge of the particle?
3) -4.0 mC
A charged particle moves in a region of uniform magnetic field along a helical path (radius = 4.0 cm, pitch = 20 cm, period = 2.0 ms). What is the speed of the particle as it moves along this path?
3) 0.16 km/s
A current of 4.0 A is maintained in a single circular loop having a circumference of 80 cm. An external magnetic field of 2.0 T is directed so that the angle between the field and the plane of the loop is 20°. Determine the magnitude of the torque exerted on the loop by the magnetic forces acting upon it.
3) 0.38 N × m
A circular coil (radius = 0.40 m) has 160 turns and is in a uniform magnetic field. When the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.16 N × m when the current in the coil is 4.0 mA. What is the magnitude of the magnetic field?
3) 0.50 T
A 0.5-H inductor is connected into a 110 V-rms 60-Hz voltage source, with an ammeter in series. What is the rms value of the current through the inductor?
3) 0.584 A (rms)
What is the magnetic force on a 2.0-m length of (straight) wire carrying a current of 30 A in a region where a uniform magnetic field has a magnitude of 55 mT and is directed at an angle of 20° away from the wire?
3) 1.1 N
A 500-eV electron and a 300-eV electron trapped in a uniform magnetic field move in circular paths in a plane perpendicular to the magnetic field. What is the ratio of the radii of their orbits?
3) 1.3
What is the average power dissipation in an RLC series circuit with R = 10W, L = 0.1 H, C = 10 mF when driven at resonance by a 100 V-rms source?
3) 1000 W
A proton is accelerated from rest through a potential difference of 150 V. It then enters a region of uniform magnetic field and moves in a circular path (radius = 12 cm). What is the magnitude of the magnetic field in this region?
3) 15 mT
If R = 10 ohms, L = 0.1 henry, C = 10 mF, what is the resonant frequency for the parallel RLC-circuit?
3) 159 Hz
A segment of wire carries a current of 25 A along the x axis from x = -2.0 m to x = 0 and then along the z axis from z = 0 to z = 3.0m. In this region of space, the magnetic field is equal to 40 mT in the positive z direction. What is the magnitude of the force on this segment of wire?
3) 2.0 N
An electron has a velocity of 6.0 ´ 106 m/s in the positive x direction at a point where the magnetic field has the components Bx = 3.0 T, By = 1.5 T, and Bz = 2.0 T. What is the magnitude of the acceleration of the electron at this point?
3) 2.6 ´ 1018 m/s2
A deuteron is accelerated from rest through a 10-kV potential difference and then moves perpendicularly to a uniform magnetic field with B = 1.6 T. What is the radius of the resulting circular path? (deuteron: m = 3.3 ´ 10-27 kg, q = 1.6 ´ 10-19 C)
3) 20.3 mm
The voltage 8.00 sin (400t) is applied to a series RLC circuit, with R = 200W, L = 0.100 H, and C = 1.00 mF. What are the impedance Z and the phase angle q?
3) 2470 W, -85.4°
Two single charged ions moving perpendicularly to a uniform magnetic field (B = 0.4 T) with speeds of 5000 km/s follow circular paths that differ in diameter by 5.0 cm. What is the difference in the mass of these two ions?
3) 3.2 ´ 10-28 kg
A proton with a kinetic energy of 0.20 keV follows a circular path in a region where the magnetic field is uniform and has a magnitude of 60 mT. What is the radius of this path?
3) 3.4 cm
An electron moves in a region where the magnetic field is uniform, has a magnitude of 60 mT, and points in the positive x direction. At t = 0 the electron has a velocity that has an x component of 30 km/s, a y component of 40 km/s, and a z component of zero. What is the radius of the resulting helical path?
3) 3.8 mm
A particle (q = 5.0 nC, m = 3.0 mg) moves in a region where the magnetic field has components Bx = 2.0 mT, By = 3.0 mT, and Bz = -4.0 mT. At an instant when the speed of the particle is 5.0 km/s and the direction of its velocity is 120° relative to the magnetic field, what is the magnitude of the acceleration of the particle?
3) 39 m/s2
An ac generator with peak voltage 100 volts is placed across a 10-W resistor. What is the average power dissipated?
3) 500 W
If an R = 1-kW resistor, a C = 1-mF capacitor, and an L = 0.2-H inductor are connected in series with a V = 150 sin (377t) volts source, what is the maximum current delivered by the source?
3) 54 mA
A rectangular coil (0.20 m ´ 0.80 m) has 200 turns and is in a uniform magnetic field of 0.30 T. When the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.080 N × m. What is the current in the coil?
3) 8.3 mA
A charged particle (mass = M, charge = Q > 0) moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with a speed V?
3) QVB toward the west
A charged particle (mass = M, charge = Q > 0) moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with speed V?
3) QVB toward the west
You stand near the earth's equator. A positively charged particle that starts moving parallel to the surface of the earth in a straight line directed east is initially deflected upwards. If you know there are no electric fields in the vicinity, a possible reason why the particle does not initially acquire a downward component of velocity is because near the equator the magnetic field lines of the earth are directed
3) from south to north.
How long will it take a charged 80-mF capacitor to lose 20% of its initial energy when it is allowed to discharge through a 45-W resistor?
3)0.40 ms
In an RC circuit, how many time constants must elapse if an initially uncharged capacitor is to reach 80% of its final potential difference?
3)1.6
The battery is disconnected from a series RC circuit after the capacitor is fully charged and is replaced by an open switch. When the switch is closed,
3)the current through the resistor is always equal to the current through the capacitor.
*A 60-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 W and L = 10.0 mH. The power factor, cos f, is
4) +0.936.
What value of B should be used in a velocity selector to separate out 2.0-keV protons if E is fixed at 80 kV/m?
4) 0.13 T
An unusual lightning strike has a vertical portion with a current of -400 A downwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 mT. In N, the force exerted by the Earth's magnetic field on the 25 m-long current is
4) 0.30 A, West.
An unusual lightning strike has a vertical portion with a positive current of +400 A upwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 mT. In N, the force exerted by the Earth's magnetic field on the 25 m-long current is
4) 0.30 A, West.
How many time constants must elapse if an initially charged capacitor is to discharge 55% of its stored energy through a resistor?
4) 0.40
A velocity selector uses a fixed electric field of magnitude E and the magnetic field is varied to select particles of various energies. If a magnetic field of magnitude B is used to select a particle of a certain energy and mass, what magnitude of magnetic field is needed to select a particle of equal mass but twice the energy?
4) 0.71 B
An LC circuit is to have resonant oscillations at 5.0 MHz. Find the value of a capacitor which will work with a 1.0-mH inductor.
4) 1 pF
A 60-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 W and L = 10.0 mH. The impedance is
4) 10.7 ohms
A 230 000 V-rms powerline carries an average power PAV = 250 MW a distance of 200 km. If the total resistance of the cables is 10 ohms, what is the resistive power loss?
4) 12 MW
An ideal step-down transformer has 200 primary turns and 50 secondary turns. If 440 volts (rms) is placed across the primary, what is the current in the secondary when the load resistance is 7 ohms?
4) 15.7 A (rms)
An electron moves in a region where the magnetic field is uniform, has a magnitude of 60 mT, and points in the positive x direction. At t = 0 the electron has a velocity that has an x component of 30 km/s, a y component of 40 km/s, and a z component of zero. What is the pitch of the resulting helical path?
4) 18 mm
What is the magnitude of the magnetic force on a charged particle (Q = 5.0 mC) moving with a speed of 80 km/s in the positive x direction at a point where Bx = 5.0 T, By = -4.0 T, and Bz = 3.0 T?
4) 2.0 N
A high-voltage powerline operates at 500 000 V-rms and carries an rms current of 500 A. If the resistance of the cable is 0.050W/km, what is the resistive power loss in 200 km of the powerline?
4) 2.5 Megawatts
*A 2-mF capacitor in series with a 2-kW resistor is connected to a 60-Hz ac source. Calculate the impedance of the circuit.
4) 2400 ohms
If 480 C pass through a 4.0-W resistor in 10 min, what is the potential difference across the resistor?
4) 3.2V
A straight wire of length L carries a current I in the positive z direction in a region where the magnetic field is uniform and specified by Bx = 3B, By = -2B, and Bz = B, where B is a constant. What is the magnitude of the magnetic force on the wire?
4) 3.6 ILB
A segment of wire carries a current of 25 A along the x axis from x = -2.0 m to x = 0 and then along the y axis from y = 0 to y = 3.0 m. In this region of space, the magnetic field is equal to 40 mT in the positive z direction. What is the magnitude of the force on this segment of wire?
4) 3.6 N
A resistor of unknown resistance and a 15-W resistor are connected across a 20-V emf in such a way that a 2.0 A current is observed in the emf. What is the value of the unknown resistance?
4) 30 ohms
An electron moves in a region where the magnetic field is uniform and has a magnitude of 80 mT. The electron follows a helical path which has a pitch of 9.0 mm and a radius of 2.0 mm. What is the speed of this electron as it moves in this region?
4) 35 km/s
A particle (q = -4.0 mC, m = 5.0 mg) moves in a uniform magnetic field with a velocity having a magnitude of 2.0 km/s and a direction that is 50° away from that of the magnetic field. The particle is observed to have an acceleration with a magnitude of 5.8 m/s2. What is the magnitude of the magnetic field?
4) 4.7 mT
A proton moves around a circular path (radius = 2.0 mm) in a uniform 0.25-T magnetic field. What total distance does this proton travel during a 1.0-s time interval? (m = 1.67 ´ 10-27 kg, q = 1.6 ´ 10-19 C)
4) 48 km
What current must be maintained in a square loop (50 cm on a side) to create a torque of 1.0 N × m about an axis through its center and parallel to one of its sides when a magnetic field of magnitude 70 mT is directed at 40° to the plane of the loop?
4) 75 A
A circular loop (radius = 0.50 m) carries a current of 3.0 A and has unit normal vector of (2i - j + 2k)/3. What is the x component of the torque on this loop when it is placed in a uniform magnetic field of (2i - 6j)T?
4) 9.4 N × m
In a typical transmission line, the current I is very small and the voltage V is very large. A unit length of line has resistance R. For a power line that supplies power to 10,000 households, we can conclude that
4) IV > I2R.
Equal charges, one at rest, the other having a velocity of 104 m/s, are released in a uniform magnetic field. Which charge has the largest force exerted on it by the magnetic field?
4) The charge that is moving if its velocity is perpendicular to the magnetic field direction when it is released.
A particle (m = 3.0 mg, q = 5.0 mC) moves in a uniform magnetic field given by (60j) mT. At t = 0 the velocity of the particle is equal to (30j - 40k) m/s. The subsequent path of the particle is
4) helical with a 40-cm radius.
One reason why we know that magnetic fields are not the same as electric fields is because the force exerted on a charge +q
4) is parallel to an electric field and perpendicular to a magnetic field.
Whenever the alternating current frequency in a series RLC circuit is halved,
4) the inductive reactance is halved and the capacitive reactance is doubled.
In a loop in a closed circuit, the sum of the currents entering a junction equals the sum of the currents leaving a junction because
5) Charge is neither created nor destroyed at a junction.
