Question: What minimum number of 75 - W light-

> Mass m = 1.00 kg is suspended vertically at rest by an insulating string connected to a circuit partially immersed in a magnetic field as in Figure P19.30. The magnetic field has magnitude Bin = 2.00 T and the length â„“ = 0.500 m. (a) Fi

> A wire with a mass of 1.00 g/cm is placed on a horizontal surface with a coefficient of friction of 0.200. The wire carries a current of 1.50 A eastward and moves horizontally to the north. What are the magnitude and the direction of the smallest vertica

> At a certain location, Earth has a magnetic field of 0.60 x 10-4 T, pointing 75° below the horizontal in a north–south plane. A 10.0 - m - long straight wire carries a 15 - A current. (a) If the current is directed horizontally toward the east, what are

> A wire carries a current of 10.0 A in a direction that makes an angle of 30.0° with the direction of a magnetic field of strength 0.300 T. Find the magnetic force on a 5.00 - m length of the wire.

> A wire having a mass per unit length of 0.500 g/cm carries a 2.00 - A current horizontally to the south. What are the direction and magnitude of the minimum magnetic field needed to lift this wire vertically upward?

> In Figure P19.3, assume in each case the velocity vector shown is replaced with a wire carrying a current in the direction of the velocity vector. For each case, find the direction of the magnetic field that will produce the magnetic force shown. Figure

> A straight wire carrying a 3.0 - A current is placed in a uniform magnetic field of magnitude 0.28 T directed perpendicular to the wire. (a) Find the magnitude of the magnetic force on a section of the wire having a length of 14 cm. (b) Explain why you c

> Which of the following actions would double the magnitude of the magnetic force per unit length between two parallel current - carrying wires? Choose all correct answers. (a) Double one of the currents. (b) Double the distance between them. (c) Reduce th

> A current I = 15 A is directed along the positive x - axis and perpendicular to a magnetic field. A magnetic force per unit length of 0.12 N/m acts on the conductor in the negative y - direction. Calculate the magnitude and direction of the magnetic fiel

> In Figure P19.2, assume in each case the velocity vector shown is replaced with a wire carrying a current in the direction of the velocity vector. For each case, find the direction of the magnetic force acting on the wire. Figure P19.2:

> A particle passes through a mass spectrometer as illustrated in Figure P19.15. The electric field between the plates of the velocity selector has a magnitude of 8250 V/m, and the magnetic fields in both the velocity selector and the deflection chamber ha

> A proton (charge +e, mass mp), a deuteron (charge +e, mass 2mp), and an alpha particle (charge +2e, mass 4mp) are accelerated from rest through a common potential difference ΔV. Each of the particles enters a uniform magnetic field B(, with its velocity

> A proton is at rest at the plane vertical boundary of a region containing a uniform vertical magnetic field B (Fig. P19.19). An alpha particle moving horizontally makes a head - on elastic collision with the proton. Immediately after the collision, both

> Two long, straight wires cross each other at right angles, and each carries the same current as in Figure CQ19.18. Which of the following statements are true regarding the total magnetic field at the various points due to the two wires? (There may be mor

> Jupiter’s magnetic field occupies a volume of space larger than the Sun and contains ionized particles ejected from sources including volcanoes on Io, one of Jupiter’s moons. A sulfur ion (S+) in Jupiter’s magnetic field has mass 5.32 x 10-26 kg and kine

> Figure CQ19.16 shows four permanent magnets, each having a hole through its center. Notice that the blue and yellow magnets are levitated above the red ones. (a) How does this levitation occur? (b) What purpose do the rods serve? (c) What can you say abo

> Consider the mass spectrometer shown schematically in Figure P19.15. The electric field between the plates of the velocity selector is 9.50 x 102 V/m, and the magnetic fields in both the velocity selector and the deflection chamber have magnitudes of 0.9

> How can a current loop be used to determine the presence of a magnetic field in a given region of space?

> A square and a circular loop with the same area lie in the xy - plane, where there is a uniform magnetic field B( pointing at some angle θ with respect to the positive z - direction. Each loop carries the same current, in the same direction. Which magnet

> An electron moves in a circular path perpendicular to a magnetic field of magnitude 0.235 T. If the kinetic energy of the electron is 3.30 x 10-19 J, find (a) The speed of the electron and (b) The radius of the circular path.

> Why do charged particles from outer space, called cosmic rays, strike Earth more frequently at the poles than at the equator?

> At the equator, near the surface of Earth, the magnetic field is approximately 50.0 μT northward, and the electric field is about 100. N/C downward in fair weather. Find the gravitational, electric, and magnetic forces on an electron with an instantaneou

> Is the magnetic field created by a current loop uniform? Explain.

> A proton moving at 4.00 x 106 m/s through a magnetic field of magnitude 1.70 T experiences a magnetic force of magnitude 8.20 x 10-13 N. What is the angle between the proton’s velocity and the field?

> A magnet attracts a piece of iron. The iron can then attract another piece of iron. On the basis of domain alignment, explain what happens in each piece of iron.

> Electrons and protons travel from the Sun to the Earth at a typical velocity of 4.00 x 105 m/s in the positive x - direction. Thousands of miles from Earth, they interact with Earth’s magnetic field of magnitude 3.00 x 10-8 T in the positive z - directio

> Will a nail be attracted to either pole of a magnet? Explain what is happening inside the nail when it is placed near the magnet.

> A laboratory electromagnet produces a magnetic field of magnitude 1.50 T. A proton moves through this field with a speed of 6.00 x 106 m/s. (a) Find the magnitude of the maximum magnetic force that could be exerted on the proton. (b) What is the magnitud

> Can a constant magnetic field set a proton at rest into motion? Explain your answer.

> As a charged particle moves freely in a circular path in the presence of a constant magnetic field applied perpendicular to the particle’s velocity, the particle’s kinetic energy (a) Remains constant, (b) Increases, or (c) Decreases.

> The circuit in Figure P18.62 contains two resistors, R1 = 2.0 kΩ and R2 = 3.0 kΩ, and two capacitors, C1 = 2.0 μF and C2 = 3.0 μF, connected to a battery with emf ε = 120 V. If there are no

> A battery with an internal resistance of 10.0 Ω produces an open circuit voltage of 12.0 V. A variable load resistance with a range from 0 to 30.0 Ω is connected across the battery. (Note: A battery has a resistance that depends o

> For the network in Figure P18.60, show that the resistance between points a and b is Rab = 27/17 Ω. (Hint: Connect a battery with emf ε across points a and b and determine ε/I, where I is the current in the battery.)

> A voltage DV is applied to a series configuration of n resistors, each of resistance R. The circuit components are reconnected in a parallel configuration, and voltage ΔV is again applied. Show that the power consumed by the series configuration is 1/n2

> A circuit consists of three identical lamps, each of resistance R, connected to a battery as in Figure P18.53. (a) Calculate an expression for the equivalent resistance of the circuit when the switch is open. Repeat the calculation when the switch is clo

> The circuit in Figure P18.52a consists of three resistors and one battery with no internal resistance. (a) Find the current in the 5.00 - Ω resistor. (b) Find the power delivered to the 5.00 - Ω resistor. (c) In each of the circui

> When two unknown resistors are connected in series with a battery, the battery delivers 225 W and carries a total current of 5.00 A. For the same total current, 50.0 W is delivered when the resistors are connected in parallel. Determine the value of each

> Three 60.0 - W, 120 - V light-bulbs are connected across a 120 - V power source, as shown in Figure P18.50. Find (a) The total power delivered to the three bulbs and (b) The potential difference across each. Assume the resistance of each bulb is constant

> Figure P18.49 shows separate series and parallel circuits. (a) What is the ratio ΔVseries /ΔVparallel? (b) What is the ratio of the power dissipated by the resistors in the series to the parallel circuit, Pseries/Pparallel? Figur

> The resistor R in Figure P18.58 dissipates 20 W of power. Determine the value of R. Figure P18.58:

> For the circuit shown in Figure P18.48, the voltmeter reads 6.0 V and the ammeter reads 3.0 mA. Find (a) The value of R, (b) The emf of the battery, and (c) The voltage across the 3.0 – kΩ resistor. (d) What assumptions did

> (a) Calculate the potential difference between points a and b in Figure P18.47 and (b) Identify which point is at the higher potential. Figure P18.47:

> How many different resistance values can be constructed from a 2.0 - Ω, a 4.0 - Ω, and a 6.0 - Ω resistor? Show how you would get each resistance value either individually or by combining them.

> Using Figure 18.29b and the results of Problems 18.43d and 18.44a, find the power supplied by the axon per action potential. Figure 18.29b:

> Consider the model of the axon as a capacitor from Problem 43 and Figure P18.43. (a) How much energy does it take to restore the inner wall of the axon to -7.0 x 10-2 V, starting from +3.0 x 10-2 V? (b) Find the average current in the axon wall during th

> Assume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration = 50.0 m/s x 2.0 x 10-3 s = 0.10 m). In the resting state, the outer surface of the axon wall is charged positively with K+

> A coffee maker is rated at 1200 W, a toaster at 1100 W, and a waffle maker at 1400 W. The three appliances are connected in parallel to a common 120 - V household circuit. (a) What is the current in each appliance when operating independently? (b) What t

> A heating element in a stove is designed to dissipate 3.00 x 103 W when connected to 240. V. (a) Assuming the resistance is constant, calculate the current in the heating element if it is connected to 120. V. (b) Calculate the power it dissipates at that

> A 1 150 - W toaster and an 825 - W microwave oven are connected in parallel to the same 20.0 - A, 120 - V circuit. (a) Find the toaster’s resistance R. (b) If the microwave fails and is replaced, what maximum power rating can be used without tripping the

> The student engineer of a campus radio station wishes to verify the effectiveness of the lightning rod on the antenna mast (Fig. P18.57). The unknown resistance Rx is between points C and E. Point E is a “true ground”

> The capacitor in Figure P18.35 is uncharged for t (a) t = 0, when the switch is closed, and (b) t = (, one time constant after the switch is closed. Figure P18.35:

> Figure P18.37 shows a simplified model of a cardiac defibrillator, a device used to resuscitate patients in ventricular fibrillation. When the switch S is toggled to the left, the capacitor C charges through the resistor R. When the switch is toggled to

> The RC charging circuit in a camera flash unit has a voltage source of 275 V and a capacitance of 125 μF. (a) Find its resistance R if the capacitor charges to 90.0% of its final value in 15.0 s. (b) Find the average current delivered to the flash bulb i

> Consider a series RC circuit as in Figure P18.35 for which R = 1.00 MΩ, C = 5.00 μF, and ε = 30.0 V. Find (a) The time constant of the circuit and (b) The maximum charge on the capacitor after the switch is thrown c

> An uncharged capacitor and a resistor are connected in series to a source of emf. If ε = 9.00 V, C = 20.0 μF, and R = 1.00 x 102 Ω, find (a) The time constant of the circuit, (b) The maximum charge on the capacitor, and (c) The charge on the capacitor af

> Consider the series RC circuit shown in Figure 18.17 for which R = 75.0 kΩ, C = 25.0 μF, and ε = 12.0 V. Find (a) The time constant of the circuit and (b) The charge on the capacitor one time constant after the swit

> Show that ( = RC has units of time.

> Find the potential difference across each resistor in Figure P18.31. Figure P18.31:

> For the circuit shown in Figure P18.30, use Kirchhoff’s rules to obtain equations for (a) The upper loop, (b) The lower loop, and (c) The node on the left side. In each case suppress units for clarity and simplify, combining like terms.

> (a) Can the circuit shown in Figure P18.29 be reduced to a single resistor connected to the batteries? Explain. (b) Find the magnitude of the current and its direction in each resistor. Figure P18.29:

> An emf of 10 V is connected to a series RC circuit consisting of a resistor of 2.0 x 106 Ω and an initially uncharged capacitor of 3.0 μF. Find the time required for the charge on the capacitor to reach 90% of its final value.

> A dead battery is charged by connecting it to the live battery of another car with jumper cables (Fig. P18.28). Determine the current in (a) The starter and in (b) The dead battery. Figure P18.28:

> (a) Can the circuit shown in Figure P18.27 be reduced to a single resistor connected to the batteries? Explain. (b) Calculate each of the unknown currents I1, I2, and I3 for the circuit. Figure P18.27:

> Figure P18.26 shows a voltage divider, a circuit used to obtain a desired voltage ΔVout from a source voltage ε. Determine the required value of R2 if ε = 5.00 V, ΔVout = 1.50 V, and R1 = 1.00 x 103 &Icir

> Using Kirchhoff’s rules, (a) Find the current in each resistor shown in Figure P18.25 and (b) Find the potential difference between points c and f. Figure P18.25:

> Four resistors are connected to a battery with a terminal voltage of 12 V, as shown in Figure P18.24. (a) How would you reduce the circuit to an equivalent single resistor connected to the battery? Use this procedure to find the equivalent resistance of

> In the circuit of Figure P18.23, determine (a) The current in each resistor, (b) The potential difference across the 2.00 x 102 - Ω resistor, and (c) The power delivered by each battery. Figure P18.23:

> In the circuit of Figure P18.22, the current I1 is 3.0 A and the values of ε and R are unknown. What are the currents I2 and I3? Figure P18.22:

> Taking R = 1.00 kΩ and ε = 250. V in Figure P18.21, determine the direction and magnitude of the current in the horizontal wire between a and e. Figure P18.21:

> For the circuit shown in Figure P18.20, calculate (a) The current in the 2.00 - Ω resistor and (b) The potential difference between points a and b, ΔV = Vb – V. Figure P18.20:

> Figure P18.19 shows a Wheatstone bridge, a circuit used to precisely measure an unknown resistance R by varying Rvar until the ammeter reads zero current and the bridge is said to be “balanced.” If the bridge is balanc

> The circuit in Figure P18.55 has been connected for several seconds. Find the current (a) In the 4.00 - V battery, (b) In the 3.00 - Ω resistor, (c) In the 8.00 - V battery, and (d) In the 3.00 - V battery. (e) Find the charge on the capacito

> (a) Find the current in each resistor of Figure P18.18 by using the rules for resistors in series and parallel. (b) Write three independent equations for the three currents using Kirchhoff’s laws: one with the node rule; a second using

> (a) You need a 45 - Ω resistor, but the stockroom has only 20. - Ω and 50. - Ω resistors. How can the desired resistance be achieved under these circumstances? (b) What can you do if you need a 35 - Ω resistor?

> (a) Is it possible to reduce the circuit shown in Figure P18.16 to a single equivalent resistor connected across the battery? Explain. (b) Find the current in the 2.00 - Ω resistor. (c) Calculate the power delivered by the battery to the circ

> Find the current in the 12 - Ω resistor in Figure P18.15. Figure P18.15:

> A 2.00 - nF capacitor with an initial charge of 5.10 μC is discharged through a 1.30 – kΩ resistor. (a) Calculate the magnitude of the current in the resistor 9.00 μs after the resistor is connected across the terminals of the capacitor. (b) What charge

> The given pair of capacitors in Figure P18.67 is fully charged by a 12.0 - V battery. The battery is disconnected and the circuit closed. After 1.00 ms, how much charge remains on (a) The 3.00 - μF capacitor? (b) The 2.00 - μF

> Consider the two arrangements of batteries and bulbs shown in Figure P18.66. The two bulbs are identical and have resistance R, and the two batteries are identical with output voltage ΔV. (a) In case 1, with the two bulbs in series, compare t

> What are the expected readings of the ammeter and voltmeter for the circuit in Figure P18.65? Figure P18.65:

> In Figure P18.64, R1 = 0.100 Ω, R2 = 1.00 Ω, and R3 = 10.0 Ω. Find the equivalent resistance of the circuit and the current in each resistor when a 5.00 - V power supply is connected between (a) Points A and B, (b) Poi

> An electric eel generates electric currents through its highly specialized Hunter’s organ, in which thousands of disk - shaped cells called electrocytes are lined up in series, very much in the same way batteries are lined up inside a flashlight. When ac

> The resistance between points a and b in Figure P18.54 drops to one - half its original value when switch S is closed. Determine the value of R. Figure P18.54:

> Three liquids are at temperatures of 10°C, 20°C, and 30°C, respectively. Equal masses of the first two liquids are mixed, and the equilibrium temperature is 17°C. Equal masses of the second and third are then mixed, and the equilibrium temperature is 28°

> An automobile has a mass of 1500 kg, and its aluminum brakes have an overall mass of 6.00 kg. (a) Assuming all the internal energy transformed by friction when the car stops is deposited in the brakes and neglecting energy transfer, how many times could

> An iron plate is held against an iron wheel so that a sliding frictional force of 50. N acts between the two pieces of metal. The relative speed at which the two surfaces slide over each other is 40. m/s. (a) Calculate the rate at which mechanical energy

> A bar of gold (Au) is in thermal contact with a bar of silver (Ag) of the same length and area (Fig. P11.63). One end of the compound bar is maintained at 80.0°C, and the opposite end is at 30.0°C. Find the temperature at the juncti

> A class of 10 students taking an exam has a power output per student of about 200 W. Assume the initial temperature of the room is 20°C and that its dimensions are 6.0 m by 15.0 m by 3.0 m. What is the temperature of the room at the end of 1.0 h if all t

> Liquid helium has a very low boiling point, 4.2 K, as well as a very low latent heat of vaporization, 2.00 x 104 J/kg. If energy is transferred to a container of liquid helium at the boiling point from an immersed electric heater at a rate of 10.0 W, how

> Overall, 80% of the energy used by the body must be eliminated as excess thermal energy and needs to be dissipated. The mechanisms of elimination are radiation, evaporation of sweat (2430 kJ/kg), evaporation from the lungs (38 kJ/h), conduction, and conv

> The temperature of a silver bar rises by 10.0°C when it absorbs 1.23 kJ of energy by heat. The mass of the bar is 525 g. Determine the specific heat of silver from these data.

> A student measures the following data in a calorimetry experiment designed to determine the specific heat of aluminum: Initial temperature of water and calorimeter: 70.0°C Mass of water: 0.400 kg Mass of calorimeter: 0.040 kg Specific heat of

> The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0°C. The person is located in a dark room with a temperature of 20.0°C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) Wh

> In an analogy between traffic flow and electrical current, (a) What would correspond to the charge Q? (b) What would correspond to the current I?

> A 0.040.-kg ice cube floats in 0.200 kg of water in a 0.100-kg copper cup; all are at a temperature of 0°C. A piece of lead at 98°C is dropped into the cup, and the final equilibrium temperature is 12°C. What is the mass of the lead?

> A family comes home from a long vacation with laundry to do and showers to take. The water heater has been turned off during the vacation. If the heater has a capacity of 50.0 gallons and a 4800-W heating element, how much time is required to raise the t

> The bottom of a copper kettle has a 10.0-cm radius and is 2.00 mm thick. The temperature of the outside surface is 102°C, and the water inside the kettle is boiling at 1 atm of pressure. Find the rate at which energy is being transferred through the bott

> The filament of a 75-W light bulb is at a temperature of 3300 K. Assuming the filament has an emissivity e = 1.0, find its surface area.

> Measurements on two stars indicate that Star X has a surface temperature of 5727°C and Star Y has a surface temperature of 11727°C. If both stars have the same radius, what is the ratio of the luminosity (total power output) of Star Y to the luminosity o

> A granite ball of radius 2.00 m and emissivity 0.450 is heated to 135°C. (a) Convert the given temperature to Kelvin. (b) What is the surface area of the ball? (c) If the ambient temperature is 25.0°C, what net power does the ball radiate?