exam 2

What current flows through a 2.93 cm diameter rod of pure silicon that is 21.5 cm long, when 1000 V is applied to it? (Such a rod may be used to make nuclear particle detectors, for example.) The resistivity of pure silicon is 2.30 103 Ω · m.

20B post #1 1.36282e-3 A

Suppose an electrical wire is replaced with one having every linear dimension doubled (i.e., the length and radius have twice their original values). How is the resistance of the wire affected? The wire has less resistance than before. The wire has more resistance than before. The wire has the same resistance as before

20B pre #2 The wire has less resistance than before.

All electric devices are required to have identifying plates that specify their electrical characteristics. The plate on a certain steam iron states that the iron carries a current of 6.00 A when connected to a source of 1.20 ✕ 102 V. What is the resistance of the steam iron? 0.050 Ω 36.0 Ω 20.0 Ω

20B pre #3 20.0 Ω

A copper wire has a resistance of 0.435 Ω at 20.0°C, and an iron wire has a resistance of 0.454 Ω at the same temperature. At what temperature are their resistances equal? The temperature coefficient of resistivity for copper is 3.90 10-3(°C)−1 and for iron it is 5.00 10-3(°C)−1.

20C post #1 -13.1299 °C

If a certain silver wire has a resistance of 8.00 Ω at 11.0°C, what resistance will it have at 25.0°C?

20C pre #2 8.4256 Ω

A hair dryer has a switch that allows it to be used in the US (where the AC voltage is 120 V) and in Europe (where the AC voltage is 230 V). It accomplishes this by having two different resistance settings. When the switch is in the "120 V" position, the hair dryer uses a resistance value that allows it to operate at its rated power of 1910 W when connected to 120 V, and when the switch is in the "230 V" setting, the hair dryer uses a resistance that allows it to still operate at its rated power of 1910 W when connected to 230 V. A tourist takes her 1910 W dual voltage hair dryer to Europe but forgets to set the switch to the "230 V" position. When she plugs it into the 230 V receptacle and turns it on, it begins to smoke. What power does the hair dryer consume as a result of this mistake?

20D post #1 7016.59722 W

Two lightbulbs are each connected to a voltage of 120 V. One has a power of 25 W, the other 100 W. Which bulb has the higher resistance? 25 W bulb 100 W bulb Which bulb carries more current? 25 W bulb 100 W bulb

20D post #2 25 W bulb 100 W bulb

A battery of voltage V delivers power P to a resistor of resistance R connected to it. By what factor will the power delivered to the resistor change if the following changes are made? Give your answers as a factor of the original power P. (a) The resistance is changed to 3.40R. (b) The voltage of the battery is now 3.40V, but the resistance is R. (c) The resistance is 3.40R and voltage is 3.40V. (d) The resistance is 3.40R and the voltage is V/3.40.

20D post #3 a .2941176 P b 11.56 P c 3.4 P d .025442703 P

You and your housemate have an argument over the cost of the electric bill. You want to turn off the outside porch light before going to bed each night. Your housemate wishes to keep the light on from 6:00 PM each evening to 6:00 AM the next morning and says that this will not add any significant amount to the electric bill. If the porch light bulb is a 75 W bulb, how much will your housemate's plan contribute to the electric bill each month? Take the number of days in a month as 30 and the average cost of electricity is 13.4¢/kW · h.

20D post #4 $3.618

Assuming 95.0% efficiency for the conversion of electrical power by the motor, what current must the 12.0-V batteries of a 823-kgelectric car be able to supply to do the following? (a) accelerate from rest to 25.0 m/s in 1.00 min (b) climb a 200-m high hill in 2.00 min at a constant 25.0 m/s speed while exerting 463 N of force to overcome air resistance and friction

20D post #5 a 376.00512 A b 2194.5029 A

What power (in kW) is supplied to the starter motor of a large truck that draws 245 A of current from a 24.0 V battery hookup?

20D pre #2 5.88 kW

When an AC source is connected across a 16.0 Ω resistor, the output voltage is given by Δv = (150 V)sin(40𝜋t). Determine the following quantities. (a) maximum voltage (b) rms voltage (c) rms current (d) peak current (e) Find the current when t = 0.0045 s.

20E post #1 a 150 V b 106.066 V c 6.6291261 A d 9.375 A e 5.023376 A

An AC voltage source is connected to a resistor R = 2.00 102 Ω. The output from an AC voltage source is given by the expression V = (1.50 102 V) sin 2𝜋ft. (a) What is the rms voltage across the resistor? (b) What is the rms current flowing through the resistor?

20E post #2 a 106.066 V b 0.5303301 A

An AC voltage source and a resistor are connected in series to make up a simple AC circuit. If the source voltage is given by V = V0 sin(2𝜋ft) and the source frequency is 25.0 Hz, at what time t will the current flowing in this circuit be 76.0% of the peak current?

20E post #3 5.4961 ms

Certain heavy industrial equipment uses AC power that has a peak voltage of 671 V. What is the rms voltage?

20E pre #2 474.397 V

What is the peak current through a 458 W room heater that operates on 120 V AC power?

20E pre #3 5.397582 A

a. What is the resistance (in Ω) of a 235 V AC short circuit that generates a peak power of 96.0 kW? b. What would the average power (in kW) be if the voltage was 120 V AC?

20F post #1 a 1.150521 Ω b 12.521739 kW

Find the current through a person and identify the likely effect on her if she touches a 120 V AC source in the following circumstances. (Note that currents above 10 mA lead to involuntarily muscle contraction.) a. Find the current (in mA) if she is standing on a rubber mat and offers a total resistance of 370 kΩ. Identify the likely effect. She will experience muscle contraction for the duration of the shock. She will feel nothing. b. Find the current (in mA) if she is standing barefoot on wet grass and has a resistance of only 3500 Ω. Identify the likely effect. She will experience muscle contraction for the duration of the shock. She will feel nothing.

20F post #2 a .3243 mA She will feel nothing. b 34.2857 mA She will experience muscle contraction for the duration of the shock.

How is a circuit breaker wired? in series with the device it is protecting in parallel with the device it is protecting neither in series or in parallel it is impossible to tell

20F pre #2 in series with the device it is protecting

In the circuit shown below, which voltmeter will measure the emf for battery 1? Neglect the small resistance in the wires. Meter C Meter A Meter D Meter B 21D post #1

21D post #1 Meter A

Which of the following statements is true regarding a voltmeter? Voltmeters have a very high resistance and are placed in series with a resistor. Voltmeters have a very low resistance and are placed in parallel with a resistor. Voltmeters have a very high resistance and are placed in parallel with a resistor. Voltmeters have a very low resistance and are placed in series with a resistor.

21D pre #2 Voltmeters have a very high resistance and are placed in parallel with a resistor.

Which of the following statements is true regarding an ammeter? Ammeters have a very high resistance and are placed in series with a resistor. Ammeters have a very high resistance and are placed in parallel with a resistor. Ammeters have a very low resistance and are placed in series with a resistor. Ammeters have a very low resistance and are placed in parallel with a resistor.

21D pre #3 Ammeters have a very low resistance and are placed in series with a resistor.

The switch is closed in the figure below. After a long time compared with the time constant of the circuit, what will the current be in the 2 Ω resistor? 21E post #1

21E post #1 2A

Which of the graphs below correctly shows the magnitude of the current versus time in a simple RC circuit during the discharging process? 21E post #2

21E post #2

Which of the graphs below correctly shows the current flowing through the resistor during the charging process in a simple RCcircuit? 21E post #3

21E post #3

The capacitor in the figure below is initially uncharged. When the switch is closed at t = 0 s, what is the voltage drop across the capacitor after one time constant has elapsed? 21E post #4

21E post #4 3.79 V

Using the exact exponential treatment, find how much time is required to discharge a 266-µF capacitor through a 489-Ω resistor down to 1.00% of its original voltage.

21E post #5 .599013 s

Which of the graphs below correctly shows the charge versus time in a simple RC circuit during the charging process? 21E pre #2

21E pre #2

Which of the graphs below correctly shows the charge versus time in a simple RC circuit during the discharging process? 21E pre #3

21E pre #3

In the figure below the current is measured with the ammeter at the bottom of the circuit. When the switch is opened, the reading on the ammeter 21a post #1

21a post #1 decreases

In the figure below, the current is measured with the ammeter on the right side of the circuit diagram. When the switch is closed, the reading on the ammeter 21a post #2

21a post #2 increases

Suppose you have three identical lightbulbs, some wire, and a battery. You connect one lightbulb to the battery and take note of its brightness. You add a second lightbulb, connecting it in parallel with the previous lightbulbs, again take note of the brightness. Repeat the process with the third lightbulb, connecting it in parallel with the other two. As the lightbulbs are added, how are the following properties affected? (Neglect the battery's internal resistance) brightness of the bulb individual currents in the bulb power delivered by the battery lifetime of the battery

21a post #3 remains unchanged remains unchanged increases decreases

Suppose you have three identical lightbulbs, some wire, and a battery. You connect one lightbulb to the battery and take note of its brightness. You add a second lightbulb, connecting it in series with the previous lightbulbs, again take note of the brightness. Repeat the process with the third lightbulb, connecting it in series with the other two. As the lightbulbs are added, how are the following properties affected? (Neglect the battery's internal resistance) brightness of the bulb individual currents in the bulb power delivered by the battery lifetime of the battery

21a post #4 decreases decreases decreases increases

Find the total resistance of the combination of resistors shown in the figure below. (R1 = 0.700 µΩ, R2 = 11.0 µΩ, and R3 = 2.50 µΩ.) 21a post #5

21a post #5 2.0598592 µΩ

Consider the circuit shown in the diagram below. The battery has a voltage V = 12.0 V and the resistors have the following values. R1 = 6.09 Ω; R2 = 12.18 Ω; R3 = 30.45 Ω; R4 = 18.27 Ω How much current flows through each of the four resistors? 21a post #6

21a post #6 I1 = 1.001373 A I2 = 0.484535 A I3 = 0.193814 A I4 = .3230235 A

In the circuit below, all four resistors are identical (R1 = R2 = R3 = R4 = R) and the battery has a voltage of 4.91 V. (a) When the switch is placed in position 1, the measured current in the battery is 1.36 mA. What is the value of each resistor? (b) When the switch is placed in position 2, what is the current flowing out of the battery? (c) When the switch is open (neither in position 1 or position 2), what is the current flowing out of the battery? 21a post #7

21a post #7 a 1.80515 kΩ b 1.088 mA c .90667 mA

A battery with an emf of 24.0 V is connected to a resistive load. If the terminal voltage of the battery is 12.7 V and the current through the load is 4.20 A, what is the internal resistance of the battery?

21a pre #2 2.6905 Ω

(a) What is the resistance of a 145 Ω, a 2.50 kΩ, and a 4.15 kΩ resistor connected in series? (b) What is the resistance if they are connected in parallel?

21a pre #2 a 6.795e3 Ω b 1.326697e2 Ω

What is the internal resistance of an automobile battery that has an emf of 12.0 V and a terminal voltage of 13.4 V while a current of 4.70 A is charging it?

21b post #1 0.29787 Ω

An automobile starter motor has an equivalent resistance of 0.0610 Ω and is supplied by a 12.0-V battery with a 0.0160-Ω internal resistance. (a) What is the current to the motor? (b) What voltage is applied to it? (c) What power is supplied to the motor? (d) Repeat these calculations for when the battery connections are corroded and add 0.0900 Ω to the circuit. (Significant problems are caused by even small amounts of unwanted resistance in low-voltage, high-current applications.)

21b post #2 a 155.8442 A b 9.5065 V c 1.4815 kW d I= 71.8563 A V= 4.3832 V P= .314963 kW

Two batteries with emf 1 and 2, with internal resistances r1 and r2 respectively, are connected as shown in the diagram below. (Assume emf1 = 12 V and r1 = 1 Ω.) (a) Calculate the magnitude and indicate the direction of flow of current in the figure shown above. 2 = 32.0 V and r2 = 0.40 Ω. (b) Find the terminal voltage of each battery. 21b post #3

21b post #3 a magnitude 14.2857 A direction counterclockwise b V1 = 26.2857 V V2 = 26.2857 V

In the circuit shown below emf = 76.0 V, R5 = 4.00 Ω, R2 = 2.20 Ω, I5 = 9.70 A, I4 = 6.60 A, and I1 = 10.9 A. Find the current through R2 and R3, and the values of the resistors R1 and R4. 21c post #1

21c post #1 I2 = 14 A I3 = 3.1 A R1 = 4.1468 Ω R4 = 5.636364 Ω

You and a group of friends are on a day trip to a nearby national park. After a fun-filled day of fishing and boating, you are ready to head back home when you find that your car battery is dead. Your friend offers to use his car's battery and jumper cables to charge yours. The connections are shown in the two diagrams below. The internal resistance of your car battery is rd = 2.93 Ω, that of your friend's battery is rL = 0.01 Ω, and that of the starter is rS = 0.06 Ω. The live battery has a voltage of 12.0 V and the dead battery in your car has a voltage of 10.0 V. What are the currents through the starter and the dead battery when the ignition switch is closed? (Enter your answer for Is to at least one decimal place.) Is = Id = 21c post #2

21c post #2 Is = 171.415 A Id =0.09722897 A

Due to a weak connection, there is a break in the circuit (shown below) between points a and b. If R1 = 4.43 Ω, R2 = 2.29 Ω, and R3 = 14.7 Ω, and the two batteries 1 and 2 have voltages of 24.0 V and 6.50 V respectively, find the potential difference Vab. Be sure to include the sign of the potential difference. Vab = Vb − Va = 21c post #3

21c post #3 -14.67857V

Which of the following equations is not a consequence of Kirchhoff's rules, when applied to the figure shown below? 21c pre #2 I1 + I2 − I3 = 0 9 − I1 − 2I2 = 0 4 − 2I2 − 3I3 = 0 All these equations are correct. 5 − I1 − 3I3 = 0

21c pre #2 9 − I1 − 2I2 = 0

The north-pole end of a bar magnet is held near a stationary positively charged piece of plastic. How is the plastic affected? The plastic is attracted by the magnet. The plastic is unaffected by the magnet. The plastic is repelled by the magnet.

22A post #1 The plastic is unaffected by the magnet.

Which of the following statements is/are true? (Select all that apply.) Magnetic monopoles have never been found in nature, and apparently do not exist. Ferromagnetic materials are noticeably attracted to North and South poles of magnets. North poles are attracted to each other. South poles repel each other. Copper is noticeably attracted to North and South poles of magnets.

22A pre #2 South poles repel each other. Ferromagnetic materials are noticeably attracted to North and South poles of magnets. Magnetic monopoles have never been found in nature, and apparently do not exist.

A bar magnet is placed in an external, uniform magnetic field as shown in the figure. Is there a resultant torque on the bar magnet, and if so, what is the direction of that torque? There is no torque. There is a counterclockwise torque. There is a clockwise torque. 22B post #1

22B post #1 There is a clockwise torque.

A person, standing on the ground, measures the earth's magnetic field to point in the direction shown in the figure. (a) Which direction should the person walk to get to the geographic north pole? to the left to the right (b) Is the person standing in the northern or southern hemisphere? Southern hemisphere Northern hemisphere

22B post #2 a To the right b Southern hemisphere

Which of the following statements is/are true? (Select all that apply.) Magnetic field lines form complete loops. Ferromagnetic materials can be magnetized more easily than other materials because their magnetic domains can be generally aligned. Unlike electric field lines, magnetic field lines can cross each other. Magnetic field lines exit the north pole of a magnet and reenter the south pole of a magnet.

22B pre #2 Magnetic field lines form complete loops. Ferromagnetic materials can be magnetized more easily than other materials because their magnetic domains can be generally aligned. Magnetic field lines exit the north pole of a magnet and reenter the south pole of a magnet.

Two charged particles are projected into a region where a magnetic field is directed perpendicular to their velocities. If the charges are deflected in opposite directions, what are the possible relative charges and directions? (Select all that apply.) oppositely charged, same initial direction same charge, opposite initial direction oppositely charged, opposite initial direction same charge, same initial direction

22C post #1 oppositely charged, same initial direction same charge, opposite initial direction

An electron moves across Earth's equator at a speed of 2.5 106 m/s and in a direction 35° N of E. At this point, Earth's magnetic field has a direction due north, is parallel to the surface, and has a magnitude of 0.10 ✕ 10-4 T. What is the force acting on the electron due to its interaction with Earth's magnetic field?

22C post #2 3.3 x 10-18 N toward Earth's surface

What is the direction of the velocity of a negative charge that experiences the magnetic force shown in each of the following three cases, assuming it moves perpendicular to B? 22C post #3

22C post #3

Using appropriate technology, you determine that Earth's magnetic field at your location has a magnitude of 5.31 10-5 T and is directed north at an angle of 57° below the horizontal. You charge a metallic projectile and fire it north with a speed of 694 m/s and at an angle of 14° above the horizontal. Determine the sign (+ or −) and charge of the projectile, if the magnetic force on the projectile is 3.20 10-10 N, directed due west.

22C post #4 9.1839 e-9 C

A proton moving in the positive x direction with a speed of 8.3 105 m/s experiences zero magnetic force. When it moves in the positive y direction it experiences a force of 2.4 10-13 N that points in the positive z direction. Determine the magnitude and direction of the magnetic field.

22C post #5 magnitude: 1.8072289 T direction: -x

A uniform magnetic field cannot exert a magnetic force on a particle in which of the following circumstances? (Select all that apply.) The particle is charged. The particle moves parallel to the field. The magnitude of the magnetic field changes with time. The particle moves perpendicular to the field. The particle is at rest.

22C pre #2 The particle moves parallel to the field The particle is at rest.

What is the direction of the magnetic force on a negative charge that moves as shown in each of the six cases? 22C pre #3

22C pre #3

What is the maximum force on a rod with a 0.100 µC charge that you pass between the poles of a 1.71 T strength permanent magnet at a speed of 4.72 m/s?

22C pre #4 8.0712e-7 N

A charged particle is traveling through a uniform magnetic field. Which of the following statements are true of the magnetic field? (Select all that apply.) It increases the kinetic energy of the particle. It exerts a force on the particle that is parallel to the field. It exerts a force on the particle along the direction of its motion. It doesn't change the magnitude of the momentum of the particle. It exerts a force that is perpendicular to the direction of motion.

22D postclass #1 It doesn't change the magnitude of the momentum of the particle. It exerts a force that is perpendicular to the direction of motion.

As shown in the figure, an electron is fired with a speed of 3.40 106 m/s through a hole in one of the two parallel plates and into the region between the plates separated by a distance of 0.29 m. There is a magnetic field in the region between the plates and, as shown, it is directed into the plane of the page (perpendicular to the velocity of the electron). Determine the magnitude of the magnetic field so that the electron just misses colliding with the opposite plate. 22D postclass #2

22D postclass #2 6.67543 e-5 T

The figure below shows the schematic for a mass spectrometer which consists of a velocity selector and a deflection chamber. The magnitude of the magnetic field in both the velocity selector and the deflection chamber is 0.0110 T, and the electric field between the plates of the velocity selector is 1100 V/m. If a singly charged ion with a mass of 8.37 10-27 kg travels through the velocity selector and into the deflection chamber, determine the radius of its trajectory in the deflection chamber. 22D postclass #3

22D postclass #3 .4755682 m

As shown in the figure below, when a charged particle enters a region of magnetic field traveling in a direction perpendicular to the field, it will travel in a circular path. If the magnitude of the magnetic field is 0.180 T, the speed of the particle is 12.0 ✕ 10^6 m/s, the radius of the trajectory of the path is 106.8 cm, and the charge has a magnitude of 3.20 x 10^-19 C, determine the following. (a) sign of the charged particle (b) mass of the particle (use the conversion 1 u = 1.66 10-27 kg) 22D postclass #4

22D postclass #4 a. positive b. 3.088193 u

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 _____

22D preclass #2 remains constant

Assume the motions and currents mentioned are along the x axis and fields are in the y direction. (a) Does an electric field exert a force on a stationary charged object? (b) Does a magnetic field do so? (c) Does an electric field exert a force on a moving charged object? (d) Does a magnetic field do so? (e) Does an electric field exert a force on a straight current-carrying wire? (f) Does a magnetic field do so? (g) Does an electric field exert a force on a beam of moving electrons? (h) Does a magnetic field do so?

22E postclass #1 a yes b no c yes d yes e no f yes g yes h yes

A current I = 19 A is directed along the positive x-axis and perpendicular to a magnetic field. A magnetic force per unit length of 0.10 N/m acts on the conductor in the negative y-direction. Calculate the magnitude and direction of the magnetic field in the region through which the current passes.

22E postclass #2 5.26e-3 T, +z direction

At a site where the Earth's magnetic field has a magnitude of 0.52 gauss (where 1 gauss = 1.00 10-4 T) and points to the north, 68° below the horizontal, a high-voltage power line 235 m in length carries a current of 120 A. Determine the magnitude and direction of the magnetic force exerted on this wire, if the orientation of the wire and hence the current is as follows. (a) horizontally toward the south (b) horizontally toward the west

22E postclass #3 A. mag: 1.3596 N direction: east at deg measured 0 below the horizontal B. mag: 1.4664 N direction: south at deg measured 22 below the horizontal

As shown in the figure, a conducting rod with a linear mass density of 0.0376 kg/m is suspended by two flexible wires of negligible mass in a uniform magnetic field directed into the page. A power supply is used to send a current through the rod such that the tension in the support wires is zero. (a) If the magnitude of the magnetic field is 3.89 T, determine the current in the conducting rod. (b) Determine the direction of the current in the conducting rod. 22E postclass #4

22E postclass #4 a. 0.094725 b. to the right

What is the direction of the magnetic force on the current in each of the six cases shown below? 22E preclass #2

22E preclass #2

A wire carries a current of 7.0 A in a direction that makes an angle of 24.0° with the direction of a magnetic field of strength 0.100 T. Find the magnetic force on a 3.00 m length of the wire.

22E preclass #3 .85415 N

A rectangular loop with a length of 0.600 m, width of 0.400 m, and consisting of 141 tightly-wrapped turns is hinged along the y-axis and placed in a uniform magnetic field such that the plane of the loop makes an angle of 35.0° with the x-axis (see figure below). The magnetic field has a magnitude of 0.880 T and points in the positive x direction, and the current in the coil is 1.25 A. (a) Determine the magnitude of the torque exerted on the loop. (b) Determine the expected direction of rotation of the loop. 22F postclass #1

22F postclass #1 a. 30.942 Nxm b. the loop rotates clockwise as viewed from above

A rectangular coil with a length of 9.0 cm and a width of 4.0 cm and 250 turns is placed in a uniform magnetic field with a magnitude of 0.91 T. (a) If the maximum torque experienced by the coil is 0.23 N · m, determine the current in the coil. (b) When the magnetic field makes an angle of 35° with the normal to the plane of the coil, determine the magnitude of the torque acting on the coil.

22F postclass #2 a. 280.8303 mA b. .131908 Nxm

A current of 20.0 mA is maintained in a single circular loop with a circumference of 3.10 m. A magnetic field of 0.490 T is directed parallel to the plane of the loop. What is the magnitude of the torque exerted by the magnetic field on the loop?

22F postclass #3 7.49445e-3 Nxm

Calculate the magnetic field strength needed on a 185-turn square loop 20.0 cm on a side to create a maximum torque of 320 N · m, if the loop is carrying 15 A.

22F preclass #2 2.883 T

Two long, parallel wires each carry the same current I in the same direction (see figure below). The total magnetic field at the point P midway between the wires is in what direction? 22G postclass #1

22G postclass #1

The figure below shows a long straight wire just touching a circular loop carrying a current I1 = 2.98 A in the counterclockwise direction. Both lie in the same plane. (a) What direction must the current I2 in the straight wire have in order to create a magnetic field at the center of the loop in the direction opposite to that created by the loop? (b) What current must the long straight wire carry in order have zero net magnetic field strength at the center of the loop?

22G postclass #2 a from right to left b 9.362 A

You have designed and constructed a solenoid to produce a magnetic field equal in magnitude to that of the Earth (5.0 10-5 T). If your solenoid has 500 turns and is 25 cmlong, determine the current you must use in order to obtain a magnetic field of the desired magnitude.

22G postclass #3 19.8944 mA

As shown in the figure, two long, straight current-carrying wires (1 and 2) are attached at right angles to a board by wire brackets. The current in wire 1 is 9.01 A in the negative y direction and the current in wire 2 is 5.00 A in the positive x direction. The points A and B are a distance r = 0.200 m from both wires (a) How does the magnitude of the net magnetic field at point A compare to the magnitude of the net magnetic field at point B? (b) Determine the magnitude of the net magnetic field at points A and B. (c) If the brackets holding wire 2 are removed, what will happen to wire 2? 22G postclass #4

22G postclass #4

If a single circular loop of wire carries a current of 74 A and produces a magnetic field at its center with a magnitude of 2.10 10-4 T, determine the radius of the loop.

22G preclass #2 .22141 m