Question: A uniform magnetic field of magnitude 0.

> A circular loop of wire lies below a long wire carrying a current that is increasing as in Figure P20.17a. (a) What is the direction of the induced current in the loop, if any? (b) Now suppose the loop is next to the same wire as in Figure P20.17b. What

> An inductor and a resistor are connected in series across an AC generator, as shown in Figure CQ21.16. Immediately after the switch is closed, which of the following statements is true? (a) The current is ΔV/R. (b) The voltage across the indu

> Why is the sum of the maximum voltages across each of the elements in a series RLC circuit usually greater than the maximum applied voltage? Doesn’t this violate Kirchhoff’s loop rule?

> A horizontal metal bar oriented east–west drops straight down in a location where Earth’s magnetic field is due north. As a result, an emf develops between the ends. Which end is positively charged? (a) The east end (b) The west end (c) Neither end carri

> A magneto is used to cause the spark in a spark plug in many lawn mowers today. A magneto consists of a permanent magnet mounted on a flywheel so that it spins past a fixed coil. Explain how this arrangement generates a large enough potential difference

> Two circular loops are side by side and lie in the xy - plane. A switch is closed, starting a counterclockwise current in the left-hand loop, as viewed from a point on the positive z - axis passing through the center of the loop. Which of the following s

> A bar magnet is falling toward the center of a loop of wire, with the north-pole oriented downward. Viewed from the same side of the loop as the magnet, as the north-pole approaches the loop, what is the direction of the induced current? (a) Clock-wise (

> Figure 20.6 is a graph of the magnitude B versus time for a magnetic field that passes through a fixed loop and is oriented perpendicular to the plane of the loop. Rank the magnitudes of the emf generated in the loop from largest to smallest at the three

> Suppose XL > XC in Figure 21.12 and, with both switches open, a piece of iron is slipped into the inductor. During this process, what happens to the brightness of the bulb? (a) It increases. (b) It decreases. (c) It doesn’t change.

> Suppose XL > XC in Figure 21.12. If switch A is left open and switch B is closed, what happens to the phase angle? (a) It increases. (b) It decreases. (c) It doesn’t change. Figure 21.12:

> Suppose XL > XC in Figure 21.12. If switch A is closed, what happens to the phase angle? (a) It increases. (b) It decreases. (c) It doesn’t change. Figure 21.12:

> If switch A is closed in Figure 21.12, what happens to the impedance of the circuit? (a) It increases. (b) It decreases. (c) It doesn’t change. Figure 21.12:

> For the circuit in Figure 21.8, is the instantaneous voltage of the source equal to (a) The sum of the maximum voltages across the elements, (b) The sum of the instantaneous voltages across the elements, or (c) The sum of the rms voltages across the elem

> Which of the following statements can be true for a resistor connected in a simple series circuit to an operating AC generator? (a) Pav = 0 and iav = 0 (b) Pav = 0 and iav > 0 (c) Pav > 0 and iav = 0 (d) Pav > 0 and iav > 0

> Which of the following statements are true about light waves? (a) The higher the frequency, the longer the wavelength. (b) The lower the frequency, the longer the wavelength. (c) Higher - frequency light travels faster than lower - frequency light. (d) T

> If a high - frequency current is passed through a solenoid containing a metallic core, the core becomes warm due to induction. Explain why the temperature of the material rises in this situation.

> In an apparatus such as the one in Figure 21.22, suppose the black disk is replaced by one with half the radius. Which of the following are different after the disk is replaced? (a) Radiation pressure on the disk (b) Radiation force on the disk (c) Radia

> The switch in the circuit shown in Figure 20.29 is closed, and the light-bulb glows steadily. The inductor is a simple air-core solenoid. An iron rod is inserted into the interior of the solenoid, increasing the magnitude of the magnetic field in the sol

> You intend to move a rectangular loop of wire into a region of uniform magnetic field at a given speed so as to induce an emf in the loop. The plane of the loop must remain perpendicular to the magnetic field lines. In which orientation should you hold t

> A long, straight wire lies in the plane of a circular coil with a radius of 0.010 m. The wire carries a current of 2.0 A and is placed along a diameter of the coil. (a) What is the net flux through the coil? (b) If the wire passes through the center of t

> A long, straight wire carrying a current of 2.00 A is placed along the axis of a cylinder of radius 0.500 m and a length of 3.00 m. Determine the total magnetic flux through the cylinder.

> Figure P20.3 shows three edge views of a square loop with sides of length â„“ = 0.250 m in a magnetic field of magnitude 2.00 T. Calculate the magnetic flux through the loop oriented (a) Perpendicular to the magnetic field, (b) 60.0&Acirc

> Find the flux of Earth’s magnetic field of magnitude 5.00 x 10-5 T through a square loop of area 20.0 cm2 (a) When the field is perpendicular to the plane of the loop, (b) When the field makes a 30.0° angle with the normal to the plane of the loop, and (

> A square, single-turn wire loop â„“ = 1.00 cm on a side is placed inside a solenoid that has a circular cross section of radius r = 3.00 cm, as shown in the end view of Figure P20.18. The solenoid is 20.0 cm long and wound with 100 turns

> Find the direction of the current in the resistor shown in Figure P20.16 (a) At the instant the switch is closed, (b) After the switch has been closed for several minutes, and (c) At the instant the switch is opened. Figure P20.16:

> A bar magnet is positioned near a coil of wire, as shown in Figure P20.15. What is the direction of the current in the resistor when the magnet is moved (a) To the left and (b) To the right? Figure P20.15:

> When the switch in Figure CQ20.12a is closed, a current is set up in the coil and the metal ring springs upward (Fig. CQ20.12b). Explain this behavior. Figure CQ20.12:

> In Figure P20.14, what is the direction of the current induced in the resistor at the instant the switch is closed? Figure P20.14:

> A technician wearing a circular metal band on his wrist moves his hand into a uniform magnetic field of magnitude 2.5 T in a time of 0.18 s. If the diameter of the band is 6.5 cm and the field is at an angle of 45° with the plane of the metal band while

> Medical devices implanted inside the body are often powered using transcutaneous energy transfer (TET), a type of wireless charging using a pair of closely spaced coils. An emf is generated around a coil inside the body by varying the current through a n

> Inductive charging is used to wirelessly charge electronic devices ranging from toothbrushes to cell phones. Suppose the base unit of an inductive charger produces a 1.00 x 10-3-T magnetic field. Varying this magnetic field magnitude changes the flux thr

> The flexible loop in Figure P20.10 has a radius of 12 cm and is in a magnetic field of strength 0.15 T. The loop is grasped at points A and B and stretched until its area is nearly zero. If it takes 0.20 s to close the loop, what is the magnitude of the

> Three loops of wire move near a long straight wire carrying a current as in Figure P20.9. What is the direction of the induced current, if any, in (a) Loop A, (b) Loop B, and (c) Loop C. Figure P20.9:

> Transcranial magnetic stimulation (TMS) is a noninvasive technique used to stimulate regions of the human brain. A small coil is placed on the scalp, and a brief burst of current in the coil produces a rapidly changing magnetic field inside the brain. Th

> A cube of edge length â„“ = 2.5 cm is positioned as shown in Figure P20.7. There is a uniform magnetic field throughout the region with components Bx = +5.0 T, By = +4.0 T, and Bz = +3.0 T. (a) Calculate the flux through the shaded face o

> A magnetic field of magnitude 0.300 T is oriented perpendicular to the plane of a circular loop. (a) Calculate the loop radius if the magnetic flux through the loop is 2.70 Wb. (b) Calculate the new magnetic flux if the loop radius is doubled.

> When a 4.0 - μF capacitor is connected to a generator whose rms output is 30. V, the current in the circuit is observed to be 0.30 A. What is the frequency of the source?

> Suppose a creature from another planet had eyes that were sensitive to infrared radiation. Describe what it would see if it looked around the room that you are now in. That is, what would be bright and what would be dim?

> North American outlets supply AC electricity with a frequency of f = 60.0 Hz while the European standard is f = 50.0 Hz. What value of capacitance provides a capacitive reactance of 1.00 kΩ (a) In North America and (b) In Europe?

> (a) For what frequencies does a 22.0 - μF capacitor have a reactance below 175 Ω? (b) What is the reactance of a 44.0 - μF capacitor over this same frequency range?

> The output voltage of an AC generator is given by Δv = (170 V) sin (60πt). The generator is connected across a 20.0 - Ω resistor. By inspection, what are the (a) Maximum voltage and (b) Frequency? Find the (c) Rms voltage across the resistor, (d) Rms cur

> A 24.0 – kΩ resistor connected to an AC voltage source dissipates an average power of 0.600 W. (a) Calculate the rms current in the resistor. (b) Calculate the rms voltage of the AC source.

> The primary coil of a transformer has N1 = 250. turns and its secondary coil has N2 = 1500. turns. If the input voltage across the primary coil is Δv = (170. V) sin ωt, what rms voltage is developed across the secondary coil?

> A series circuit contains a 3.00 - H inductor, a 3.00 - mF capacitor, and a 30.0 - V resistor connected to a 120. - V (rms) source of variable frequency. Find the power delivered to the circuit when the frequency of the source is (a) The resonance freque

> Two electrical oscillators are used in a heterodyne metal detector to detect buried metal objects (see Fig. P21.41). The detector uses two identical electrical oscillators in the form of LC circuits having resonant frequencies of 725 kHz. When the signal

> Electrosurgical units (ESUs) supply high - frequency electricity from resonant RLC circuits to cut, coagulate, or otherwise modify biological tissue. (a) Find the resonant frequency of an ESU with an inductance of L = 1.25 μH and a capacitance of 47.0 nF

> Figure P21.4 shows three lamps connected to a 120. - V AC (rms) household supply voltage. Lamps 1 and 2 have 150 - W bulbs; lamp 3 has a 100. - W bulb. For each bulb, find (a) The rms current and (b) The resistance. Figure P21.4:

> The AM band extends from approximately 500. kHz to 1600. kHz. If a 2.0 - μH inductor is used in a tuning circuit for a radio, what are the extremes that a capacitor must reach to cover the complete band of frequencies?

> The switch S in Figure 20.27 is closed at t = 0 and the current at a reference time tref > 0 is Iref. If the circuit is changed as described below and the switch is again closed at t = 0, determine whether the current I at the same time tref would be

> According to the ancient Roman architect Vitruvius, a person’s arm span (the distance from fingertip to fingertip with the arms stretched wide) is approximately equal to his or her height. For example, people 5 feet tall tend to have an arm span of 5 fee

> A group of 80 drivers in a large city is asked for the number of parking tickets they received in the previous month. What shape do you think this distribution will have? Explain.

> An instructor asks a class of 120 students how many hours they slept during the previous night. What shape do you think this distribution will have? Explain.

> The weights of coins (in grams) were obtained for coins in the United States and coins for other countries (including Mexico, Brazil, Canada, and several in Europe). a. Write a few sentences to compare the distributions of weights of coins from the Unite

> The following dotplots show the number of calories in a sample of cereals from two manufacturers: “G” = General Mills and “K” = Kelloggs. (Source: StatCrunch) a. Write a few short se

> The bar graph shows information reported in Time magazine (May 28, 2012). For each country, the percentage of music sold over the Internet and the percentage of people with access to the Internet are displayed. a. Which two countries have the largest per

> The use of the drug Prempro, a combination of two female hormones that many women take after menopause, is called hormone replacement therapy (HRT). In July 2002, a medical article reported the results of a study that was done to determine the effects of

> The following table shows the first few entries for the majors of a sample of college students. The data are stacked and coded, where 0 represents a female student and 1 represents a male student. What would be appropriate graphs to compare the distribut

> The following table shows the first few entries for the number of hours of sleep in one night for a sample of college students. The data are stacked and coded, where 0 represents a male student and 1 represents a female student. What would be appropriate

> A physician asks all of his patients to report the approximate number of cigarettes they smoke in a day. Predict the shape of the distribution of number of cigarettes smoked per day.

> A study was conducted to assess whether 5 weeks of training with virtual reality (VR) can reduce the risk of falls in adults. Thirty-four older adults underwent 15 VR training sessions consisting of walking on a treadmill with a VR simulation. At the end

> Predict the shape of the distribution of the salaries of 25 chief executive officers (CEOs). A typical value is about 50 million per year, but there is an outlier at about 200 million.

> The graph shows shoe sizes for men and women. Compare shapes, centers, and spreads, and mention if there are outliers.

> The graphs show the distribution of self-reported maximum speeds ever driven by male and female college students who drive. Compare the shapes, the centers, and the spreads and mention any outliers.

> Thirty-nine students (26 women and 13 men) reported their ideal weight (in most cases, not their current weight). The table shows the data. a. Explain why the distribution of ideal weights is likely to be bimodal if men and women are both included in th

> College students Jeannette Mujica, Ricardo Ceja Zarate, and Jessica Cerda conducted a survey in Oxnard, California, of the number of cars going through a yellow light at intersections with and without traffic cameras that are used to automatically fine d

> Create a dotplot that has at least 10 observations and does not have skew.

> Create a dotplot that has at least 10 observations and is right-skewed.

> People were asked whether they thought stem cell research was morally acceptable. The graph shows the results of two surveys, one done in 2002 and one done on 2017. What does the graph tell us about changes in opinions about stem cell research? Explain.

> People were asked whether they favored nuclear energy in 2010 and in 2016. The data were sorted by political affiliation and are shown in the following bar graph. a. How have opinions on nuclear energy changed from 2010 to 2016? (Source: Gallup.com) b. W

> Accredited law schools were ranked from 1 for the best (Harvard) down to number 181 by the Internet Legal Research Group. When you decide on a law school to attend, one of the things you might be interested in is whether, after graduation, you will be ab

> Some studies have indicated that neuro feedback may be an effective treatment for ADHD. Read excerpts from the research published in The Lancet Psychiatry and answer the questions that follow. (Source: Schönenberg et al., “Neuro feedback, sham neuro feed

> The histograms show the average global temperature per year for two 26-year ranges in degrees Fahrenheit. The range for 1880 to 1905 is on the top, and the range for 1980 to 2005 is on the bottom. Compare the two histograms for the two periods, and expla

> A group of students held their breath as long as possible and recorded the times in seconds. The times went from a low of 25 seconds to a high of 90 seconds, as you can see in the stemplot. Suggest improvements to the following histogram generated by Exc

> The following bar chart shows a comparison of breast cancer rates for those who took HRT and those who took a placebo. Explain why the graph is deceptive, and indicate what could be done to make it less so.

> For each situation, describe the type of statistical graph that could be made to answer the statistical question posted: a. We have the systolic blood pressures by gender of a large number of elderly people. Our statistical question is, “Do these elderly

> For each situation, describe the type of statistical graph that could be made to answer the statistical question posted. a. We have the systolic blood pressures by gender of a large number of elderly people. Our statistical question is, “What percentage

> The Pew Research Center gathered data in 2018 on American social media use by gender. The bar graph shows the percentage of Internet users who use these social media platforms. a. Of these three social media sites, which is most frequently used by men? B

> The Pew Research Center documents the variety of ways in which Americans use social media. The bar chart shows the frequency of use for three social media sites among adult social media users. a. Which site is used most regularly by social media users? E

> The graph shows the rates of visits to the emergency room (ER) for injuries by gender and by age. Note that we are concerned with the rate per 100 people of that age and gender in the population. (Source: National Safety Council 2004) a. Why does the Nat

> One of the authors wanted to determine the effect of changing answers on multiple-choice tests. She had advised her students that if they had changed their minds about a previous answer, they should replace their first choice with their new choice. By lo

> Patients with Alzheimer’s disease are randomly divided into two groups. One group is given a new drug, and the other is given a placebo. After six months they are given a memory test to see whether the new drug fights Alzheimer’s better than a placebo.

> Can mindful yoga have a beneficial impact on alcohol use in high-risk adolescents? Read excerpts from the research published in The Journal of Child and Family Studies and answer the questions that follow. (Source: Fishbein et al., “Behavioral and psycho

> A researcher is interested in the effect of music on memory. She randomly divides a group of students into three groups: those who will listen to quiet music, those who will listen to loud music, and those who will not listen to music. After the appropri

> Patients with multiple sclerosis are randomly assigned a new drug or a placebo and are then given a test of coordination after six months.

> Patients with high blood pressure are asked to keep food diaries recording all items they eat for a one-week period. Researchers analyze the food diary data for trends.

> The September 2017 issue of Alzheimer’s and Dementia reported on a study that found an association between drinking sugary drinks and lower brain volume. Is this likely to be a conclusion from observational studies or randomized experiments? Can we concl

> The Harvard Heart Letter reported on a study that examined the diets of 1226 older women over 15 years. They discovered that the more vegetables the women consumed, the lower their risk of dying of cardiovascular disease. From this study can we conclude

> A study was conducted to see whether participants would ignore a sign that said, “Elevator may stick between floors. Use the stairs.” The study was done at a university dorm on the ground floor of a three-level building. Those who used the stairs were sa

> An article in the journal BMC Medicine reported on a study designed to study the effect of diet on depression. Subjects suffering from moderate to severe depression were randomly assigned to one of two groups: a diet intervention group and a social suppo

> An article by Wakefield et al. in the British medical journal Lancet claimed that autism was caused by the measles, mumps, and rubella (MMR) vaccine. This vaccine is typically given to children twice, at about the age of 1 and again at about 4 years of a

> Cartilage is a smooth, rubber-like padding that protects the long bones in the body at the joints. A study by Lu et. al. in Arthritis Care & Research found that women who drank one glass of milk daily had 32% thicker, healthier cartilage than women who d

> An article in the Journal of the Academy of Nutrition and Dietetics reported on a study of diet in subjects with moderate to severe acne. Read the excerpts from the abstract and answer the questions that follow. (Source: Burris et al., “Differences in di

> People who have had strokes are often put on “blood thinners” such as aspirin or Coumadin to help prevent a second stroke. Describe the design of a controlled experiment to determine whether aspirin or Coumadin works better in preventing second strokes.

> The New England Journal of Medicine reported on a study of fish oil consumption in pregnant mothers and the subsequent development of asthma in their children. Read the excerpts from the abstract and answer the questions that follow: (Source: Bisgaard et

> A study reported by Griffin et al. compared the rate of pneumonia between 1997 and 1999 before pneumonia vaccine (PCV7) was introduced and between 2007 and 2009 after pneumonia vaccine was introduced. Read the excerpts from the abstract, and answer the q

> In a 2017 study designed to investigate the effects of exercise on second language learning, 40 subjects were randomly assigned to one of two conditions: an experimental group that engaged in simultaneous physical activity while learning vocabulary in a

> A doctor who believes strongly that antidepressants work better than “talk therapy” tests depressed patients by treating half of them with antidepressants and the other half with talk therapy. After six months the patients are evaluated on a scale of 1 t

> A group of educators want to determine how effective tutoring is in raising students’ grades in a math class, so they arrange free tutoring for those who want it. Then they compare final exam grades for the group that took advantage of the tutoring and t

> You can find many testimonials on the Internet that drinking aloe vera juice helps with digestive ailments. From these testimonials can we conclude that aloe vera juice causes digestive problems to go away? Why or why not?

> The blog NHS Choices ( February 10, 2014) noted that “there has been increasing anecdotal evidence that vitamin C may still be useful as an anticancer medicine if used in high concentrations and given directly into the vein (intravenously).” Explain what