Question: A group of students held their breath

> 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

> A uniform magnetic field of magnitude 0.50 T is directed perpendicular to the plane of a rectangular loop having dimensions 8.0 cm by 12 cm. Find the magnetic flux through the loop.

> 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

> 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

> A local public school encourages, but does not require, students to wear uniforms. The principal of the school compares the grade point averages (GPAs) of students at this school who wear uniforms with the GPAs of those who do not wear uniforms to deter

> A group of boys is randomly divided into two groups. One group watches violent cartoons for one hour, and the other group watches cartoons without violence for one hour. The boys are then observed to see how many violent actions they take in the next two

> a. A statistics class is made up of 15 men and 23 women. What percentage of the class is male? b. A different class has 234 students, and 64.1% of them are men. How many men are in the class? c. A different class is made up of 40% women and has 20 women

> Describe the design of a controlled experiment to determine whether the use of vitamin D supplements reduces the chance of broken bones in women with osteoporosis (weak bones). Assume you have 200 women with osteoporosis to work with. Your description sh

> A survey was done of men’s and women’s hands to see if the ring finger appeared longer than the index finger or not. Yes means the ring finger is longer, and No means the ring finger appears shorter or the same length

> A survey was done of men’s and women’s hands to see if the ring finger appeared longer than the index finger or not. Yes means the ring finger is longer, and No means the ring finger appears shorter or the same length

> In 2015, the National Highway Traffic Safety Administration reported the number of pedestrian fatalities in San Francisco County was 24 and that the number in Los Angeles County was 209. Can we conclude that pedestrians are safer in San Francisco than in

> Two sections of statistics are offered, the first at 8 a.m. and the second at 10 a.m. The 8 a.m. section has 25 women, and the 10 a.m. section has 15 women. A student claims this is evidence that women prefer earlier statistics classes than men do. What

> The marriage and divorce rates are given per 1000 people in various years. Find the divorce rate as a percentage of the marriage rate and comment on the trend over time. (Source: https://www.cdc.gov/nchs)

> A recent study found that highly experienced teachers may be associated with higher student achievement. Suppose fourth-grade students at an elementary school are randomly assigned to one of eight teachers. Teachers Nagle, Crouse, Warren, Tejada, and Tra

> A medical practice group consists of seven doctors, four women and three men. The women are Drs. Town, Wu, Hein, and Lee. The men are Drs. Marland, Penner, and Holmes. Sup-pose new patients are randomly assigned to one of the doctors in the group. a. Lis

> A bag of candy contains 3 red candies and 7 brown candies. A friend says the probability of reaching the bag without looking and pulling out a red candy is 30% because 3 out of 10 candies are red. Is this an example of an empirical probability or a theor

> A student flips a coin 10 times and sees that it landed on tails 4 times. Based on this, the student says that the probability of getting a tail is 40%. Is the student referring to an empirical probability or a theoretical probability? Explain.

> The projected U.S. population is given for different decades. The projected number of people 65 years of age or older is also given. Find the percentage of people 65 or over and comment on the trend over time. Numbers are in millions of people (Source: 2

> A person was trying to figure out the probability of getting two heads when flipping two coins. He flipped two coins 10 times, and in 2 of these 10 times, both coins landed heads. On the basis of this outcome, he claims that the probability of two heads

> A Monopoly player claims that the probability of getting a 4 when rolling a six-sided die is 1/6 because the die is equally likely to land on any of the six sides. Is this an example of an empirical probability or a theoretical probability? Explain.

> Suppose you are carrying out a randomized experiment to test if there is a difference in the amount of information remembered between students who take notes using a computer versus those who take notes by hand using pen and paper. You have 20 college st

> If we flip a coin 10 times, what percentage of the time will the coin land on heads? A first step to answering this question is to simulate 10 flips. Use the random number table in Appendix A to simulate flipping a coin 10 times. Let the digits 0, 1,

> A 2018 Marist poll found that interest in baseball has been declining recently in the United States. A random sample of U.S. adults were asked how much baseball they intended to watch this season. The results are shown in the following table. a. What pe

> In 2016 the Pew Research Center asked a sample of American adults which of the following they had done in the previous 12 months: read a book in any format, read a print book, read an e-book, and listened to an audio book. The percent-ages of who had eng

> In 2017 the Pew Research Center asked young adults aged 18 to 29 about their media habits. When asked, “What is the primary way you watch television?” 61% said online streaming service, 31% said cable/satellite subscription, and 5% said digital antenna.

> In California, about 92% of teens who take the written driver’s exam fail the first time they take it (www.teendrivingcourse.com). Suppose that Sam and Maria are randomly selected teenagers taking the test for the first time. a. What is the probability t

> Suppose all the days of the week are equally likely as birthdays. Alicia and David are two randomly selected, unrelated people. a. What is the probability that they were both born on Monday? b. What is the probability that Alicia OR David was born on Mon

> A 2016 Pew Research poll reported that 80% of Americans shop online. Assume the percentage is accurate. a. If two Americans are randomly selected, what is the probability that both shop online? b. If the two Americans selected are a married couple, expla