Medical Tests MCAT-TEST Online Practice Questions and Exam Preparation

Medical Tests MCAT-TEST Online Questions & Answers

• Question 631:

  Agonistic behavior, or aggression, is exhibited by most of the more than three million species of animals on this planet. Animal behaviorists still disagree on a comprehensive definition of the term, but aggressive behavior can be loosely described as any action that harms an adversary or compels it to retreat. Aggression may serve many purposes, such as food gathering, establishing territory, and enforcing social hierarchy. In a general Darwinian sense, however, the purpose of aggressive behavior is to increase the individual animal's -- and thus, the species' -- chance of survival. Aggressive behavior may be directed at animals of other species, or it may be conspecific -- that is, directed at members of an animal's own species. One of the most common examples of conspecific aggression occurs in the establishment and maintenance of social hierarchies. In a hierarchy, social dominance is usually established according to physical superiority; the classic example is that of a pecking order among domestic fowl. The dominance hierarchy may be viewed as a means of social control that reduces the incidence of attack within a group. Once established, the hierarchy is rarely threatened by disputes because the inferior animal immediately submits when confronted by a superior. Two basic types of aggressive behavior are common to most species: attack and defensive threat. Each type involves a particular pattern of physiological and behavioral responses, which tends not to vary regardless of the stimulus that provokes it. For example, the pattern of attack behavior in cats involves a series of movements, such as stalking, biting, seizing with the forepaws and scratching with the hind legs, that changes very little regardless of the stimulus -- that is, regardless of who or what the cat is attacking. The cat's defensive threat response offers another set of closely linked physiological and behavioral patterns. The cardiovascular system begins to pump blood at a faster rate, in preparation for sudden physical activity. The eyes narrow and the ears flatten against the side of the cat's head for protection, and other vulnerable areas of the body such as the stomach and throat are similarly contracted. Growling or hissing noises and erect fur also signal defensive threat. As with the attack response, this pattern of responses is generated with little variation regardless of the nature of the stimulus. Are these aggressive patterns of attack and defensive threat innate, genetically programmed, or are they learned? The answer seems to be a combination of both. A mouse is helpless at birth, but by its 12th day of life can assume a defensive threat position by backing up on its hind legs. By the time it is one month old, the mouse begins to exhibit the attack response. Nonetheless, copious evidence suggests that animals learn and practice aggressive behavior; one need look no further than the sight of a kitten playing with a ball of string. All the elements of attack -- stalking, pouncing, biting and shaking -- are part of the game which prepares the kitten for more serious situations later in life.

  The passage asserts that animal social hierarchies are generally stable because:

  A. the behavioral responses of the group are known by all its members.
  B. the defensive threat posture quickly stops most conflicts.
  C. inferior animals usually defer to their physical superiors.
  D. the need for mutual protection from other species inhibits conspecific aggression.
  C. inferior animals usually defer to their physical superiors.

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  Explanation/Reference:

  reason for the stability of these hierarchies is revealed in the final sentence of the paragraph; hierarchies are rarely threatened by disputes because the inferior animal immediately submits when confronted by a superior. Choice C, which

  paraphrases this assertion, is the correct answer.

  Choice A doesn't make any sense; even if the behavior responses of the group (whatever those behavior responses are supposed to be) are known by all of the members, this won't automatically make the hierarchy stable. The author never

  says that the defensive threat posture stops most conflicts (Choice B) or that conspecific aggression is inhibited by the need for protection from other species (Choice D), so both of these choices can be quickly eliminated.

• Question 632:

  Our sense of smell is arguably the most powerful of our five senses, but it also the most elusive. It plays a vital yet mysterious role in our lives. Olfaction is rooted in the same part of the brain that regulates such essential functions as body metabolism, reaction to stress, and appetite. But smell relates to more than physiological function: its sensations are intimately tied to memory, emotion, and sexual desire. Smell seems to lie somewhere beyond the realm of conscious thought, where, intertwined with emotion and experience, it shapes both our conscious and unconscious lives.

  The peculiar intimacy of this sense may be related to certain anatomical features. Smell reaches the brain more directly than do sensations of touch, sight, or sound. When we inhale a particular odor, air containing volatile odiferous molecules is warmed and humidified as it flows over specialized bones in the nose called turbinates. As odor molecules land on the olfactory nerves, these nerves fire a message to the brain. Thus olfactory neurons render a direct path between the stimulus provided by the outside environment and the brain, allowing us to rapidly perceive odors ranging from alluring fragrances to noisome fumes.

  Certain scents, such as jasmine, are almost universally appealing, while others, like hydrogen sulfide (which emits a stench reminiscent of rotten eggs), are usually considered repellent, but most odors evoke different reactions from person to person, sometimes triggering strong emotional states or resurrecting seemingly forgotten memories. Scientists surmise that the reason why we have highly personal associations with smells is related to the proximity of the olfactory and emotional centers of our brain. Although the precise connection between emotion and olfaction remains a mystery, it is clear that emotion, memory, and smell are all rooted in a part of the brain called the limbic lobe.

  Even though we are not always conscious of the presence of odors, and are often unable to either articulate or remember their unique characteristics, our brains always register their existence. In fact, such a large amount of human brain tissue is devoted to smell that scientists surmise the role of this sense must be profound. Moreover, neurobiological research suggests that smell must have an important function because olfactory neurons can regenerate themselves, unlike most other nerve cells. The importance of this sense is further supported by the fact that animals experimentally denied the olfactory sense do not develop full and normal brain function.

  The significance of olfaction is much clearer in animals than in human beings. Animal behavior is strongly influenced by pheromones, which are odors that induce psychological or behavioral changes and often provide a means of communicating within a species. These chemical messages, often a complex blend of compounds, are of vital importance to the insect world. Honeybees, for example, organize their societies through odor: the queen bee exudes an odor that both inhibits worker bees from laying eggs and draws drones to her when she is ready to mate. Mammals are also guided by their sense of smell. Through odors emitted by urine and scent glands, many animals maintain their territories, identify one another, signal alarm, and attract mates.

  Although our olfactory acuity can't rival that of other animal species, human beings are also guided by smell. Before the advent of sophisticated laboratory techniques, physicians depended on their noses to help diagnose illness. A century ago, it was common medical knowledge that certain bacterial infections carry the musty odor of wine, that typhoid smells like baking bread, and that yellow fever smells like meat. While medical science has moved away from such subjective diagnostic methods, in everyday life we continue to rely on our sense of small, knowingly or not, to guide us.

  It can be inferred from the passage that the emotional element of human olfaction would be better understood through investigation into:

  A. the components and functions of the limbic lobe.
  B. how pheromones regulate social behavior and organization.
  C. the composition of certain highly evocative odors.
  D. the pathway between outside environment and olfactory nerves.
  A. the components and functions of the limbic lobe.

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  Explanation/Reference:

  This asks the reader to choose a course of investigation that might lead to better understanding of the emotional element of human olfaction. Emotion and olfaction are discussed in the third paragraph. There it is stated that the "precise connection between emotion and olfaction remains a mystery" but that "it is clear that emotion, memory, and smell are all rooted in a part of the brain called the limbic lobe." From that it can be inferred that the role of olfaction in emotion would be better understood through investigation into the workings of the limbic lobe, or choice (A). Choice (C) suggests that investigation into the composition of highly evocative odors would shed light on human olfaction. But there's nothing in the passage that implies that the composition of smells effects our perception of them. So, one cannot infer choice (C) from the passage, and it's incorrect. Choice (B) states that the emotional element of human olfaction would be better understood through investigation into pheromones. However, the passage mentions pheromones in the fifth paragraph in considering animal, not human, olfaction. There's no connection made in the passage between pheromones and human olfaction, so that study of pheromones would not help scientists understand the emotional element of human olfaction. Choice (D) suggests that study of the pathway between outside environment and olfactory nerves would be helpful to our understanding of emotions and smell. The last sentence of the second paragraph states that olfactory neurons render a direct path between stimulus and brain. From this the author notes that smells reach the brain almost directly. But, the author say or imply that this anatomical fact has anything to do with the emotional aspect of olfaction. So, choice (D) is also wrong.

• Question 633:

  A particle of mass m moves in a circle of radius r at a uniform speed and makes 1 revolution per second. What is the energy of the particle?

  

  A. Option A
  B. Option B
  C. Option C
  D. Option D
  B. Option B

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  Explanation/Reference:

  We need to calculate the kinetic energy of the particle, so we'll need to use the equation K=1/2mv2, where K is the kinetic energy, m is the mass, and v is the velocity. In the question we are told that the mass is m, but we're given nothing for the speed. We can figure it out though: Since the speed of the particle is uniform, it is related to the distance d, and the time t by the equation v = d/t. Now the distance that the particle moves through in one revolution is 2r, where r is the radius of the circular path, and since the particle goes through one revolution per second, its velocity equals 2r. Now we can substitute this expression for velocity into our equation for kinetic energy, and get that K=1/2m(2r)2. This gives us the equation that K=22mr2, choice B.

• Question 634:

  An automobile reaches a velocity of 30 m/s after accelerating at 4 ms-2 for 5 seconds. What was its initial velocity?

  A. -10 m/s
  B. 0 m/s
  C. 10 m/s
  D. 20 m/s
  C. 10 m/s

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  Explanation/Reference:

  

  

• Question 635:

  Hypoxia refers to a physiological condition in which the body lacks sufficient oxygen for normal cellular functioning. Prolonged hypoxia generally leads to an inhibition of mental capacity and a reduction in the work capacity of muscle. Severe cases of hypoxia can lead to coma or even death. Depending on the cause, hypoxia can be classified into four general types:

  Hypoxic hypoxia is a type of hypoxia that occurs when the partial pressure of oxygen in the blood is too low. For example, climbers at high altitude, where the air contains less oxygen, might experience hypoxic hypoxia because the partial pressure of oxygen in the air inhaled is very low, leading to insufficient partial pressure of oxygen in the blood.

  Anemic hypoxia describes a diminished ability of the blood to transport oxygen. Several factors can influence the oxygen-carrying capacity of the blood. Primary causes of anemic hypoxia include a lower than normal number of functional erythrocytes or an insufficient quantity of hemoglobin, the oxygen- carrying molecules of the blood. Abnormal hemoglobin can also decrease the blood's capacity to carry oxygen and lead to anemic hypoxia.

  Ischemic hypoxia is caused by a decreased delivery of blood to the tissues. Localized circulatory deficiencies, such as blood clots, and global circulatory deficiencies, such as heart failure, decrease the delivery of blood to the tissues, and can therefore cause ischemic hypoxia.

  Histotoxic hypoxia results from the inability of cells to utilize the oxygen available in the blood. Causes of histotoxic hypoxia include the poisoning of cellular enzymes involved in aerobic respiration, as well as the decreased metabolic capacity of the oxidative enzymes due to vitamin deficiency. Cyanide poisoning causes histotoxic hypoxia by blocking the action of cytochrome oxidase in the electron transport chain so that tissues cannot use oxygen even though it is available.

  If cyanide is radioactively-labeled and its position traced within the cell, it will most likely be found in:

  A. the Golgi apparatus.
  B. membrane bound vesicles.
  C. the nucleus.
  D. the mitochondria.
  D. the mitochondria.

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  Explanation/Reference:

  The passage states that cyanide blocks the action of cytochrome oxidase in the electron transport chain. The enzymes of the electron transport chain, including cytochrome oxidase, are located on the inner membrane of the mitochondria. If

  cyanide blocks the action of cytochrome oxidase, it is most likely located in the same place.

  Choices A, B, and C are incorrect because these cellular locations are not involved in the electron transport chain which is blocked by cyanide action.

• Question 636:

  Bebop lives! cries the newest generation of jazz players. During the 1980s, musicians like Wynton Marsalis revived public interest in bebop, the speedy, angular music that first bubbled up out of Harlem in the early 1940s, changing the face of jazz. That Marsalis and others thought of themselves as celebrating and preserving a noble tradition is, in one sense, inevitable. After the excesses of experimental or "free" jazz in the 1960s and the electronic jazz-rock "fusion" of the 70s, it is hardly surprising that people should hearken back to a time when jazz was "purer," perhaps even at the apex of its development. But the recent enthusiasm for bebop is also ironic in light of the music's initial public reception.

  In its infancy, during the first two decades of the 20th century, jazz was played by small groups of musicians improvising variations on blues tunes and popular songs. Most of the musicians were unable to read music, and their improvisations were fairly rudimentary. Nevertheless, jazz attained international recognition in the 1920s. Two of the people most responsible for its rise in popularity were Louis Armstrong, the first great jazz soloist, and Fletcher Henderson, leader of the first great jazz band. Armstrong, with his buoyant personality and virtuosic technical skills, greatly expanded the creative range and importance of the soloist in jazz. Henderson, a pianist with extensive training in music theory, foresaw the orchestral possibilities of jazz played by a larger band. He wrote out arrangements of songs for his band members that preserved the spirit of jazz, while at the same time giving soloists a more structured musical background upon which to shape their solo improvisations. In the 1930s, jazz moved further into the mainstream with the advent of the Swing Era. Big bands in the Henderson mold, led by musicians like Benny Goodman, Count Basie and Duke Ellington, achieved unprecedented popularity with jazz-oriented "swing" music that was eminently danceable.

  Against this musical backdrop, bebop arrived on the scene. Like other modernist movements in art and literature, bebop music represented a departure from tradition in both form and content, and was met with initial hostility. Bebop tempos were unusually fast, with the soloist often playing at double time to the backing musicians. The rhythms were tricky and complex, the melodies intricate and frequently dissonant, involving chord changes and notes not previously heard in jazz. Before bebop, jazz players had improvised on popular songs such as those produced by Tin-Pan Alley, but bebop tunes were often originals with which jazz audiences were unfamiliar.

  Played mainly by small combos rather than big bands, bebop was not danceable; it demanded intellectual concentration. Soon, jazz began to lose its hold on the popular audience, which found the new music disconcerting. Compounding public alienation was the fact that bebop seemed to have arrived on the scene in a completely mature state of development, without that early phase of experimentation that typifies so many movements in the course of Western music. This was as much the result of an accident of history as anything else. The early development of bebop occurred during a three-year ban on recording in this country made necessary by the petrol and vinyl shortages of World War II. By the time the ban was lifted, and the first bebop records were made, the new music seemed to have sprung fully-formed like Athena from the forehead of Zeus. And though a small core of enthusiasts would continue to worship bebop pioneers like Charlie Parker and Dizzy Gillespie, many bebop musicians were never able to gain acceptance with any audience and went on to lead lives of obscurity and deprivation.

  According to the passage, which of the following is true about the bebop music of the 1940s?

  A. It followed the tradition of jazz from the 1920s.
  B. It differed markedly from the music of the Swing Era.
  C. It celebrated the songs of Tin-Pan Alley.
  D. It did not require great improvisational skill.
  B. It differed markedly from the music of the Swing Era.

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  Explanation/Reference:

  This is an explicit detail question asking for a true statement about bebop in the 1940s. Choice (A), that bebop followed the tradition of jazz from the 1920s, is clearly wrong because the second sentence of paragraph 3 says that bebop "represented a departure from tradition in both form and content". Choice (B), however, is correct. Paragraph 3, in its entirety, and the first sentence of paragraph 4 clearly show that bebop differed from music of the Swing Era. Bebop music was faster and harmonically more adventurous. Unlike swing music, it not danceable, and demanded intellectual concentration. Choice (C) contradicts the last sentence of paragraph 3: bebop did not celebrate the songs of Tin-Pan Alley. Bebop tunes were often originals, unfamiliar to audiences. And choice (D) is incorrect because, as the second and seventh sentences of the second paragraph indicate, bebop sprang from improvisations. Its extremely fast tempos and ever-increasing musical sophistication clearly imply that playing bebop required extensive improvisational skill.

• Question 637:

  ...Until last year many people -- but not most economists -- thought that the economic data told a simple tale. On one side, productivity -- the average output of an average worker -- was rising. And although the rate of productivity increase was very slow during the 1970's and early 1980's, the official numbers said that it had accelerated significantly in the 1990's. By 1994 an average worker was producing about 20 percent more than his or her counterpart in 1978. On the other hand, other statistics said that real, inflation- adjusted wages had not been rising at anything like the same rate. In fact, some of the most commonly cited numbers showed real wages actually falling over the last 25 years. Those who did their homework knew that the gloomiest numbers overstated the case.... Still, even the most optimistic measure, the total hourly compensation of the average worker, rose only 3 percent between 1978 and 1994.... ...But now the experts are telling us that the whole thing may have been a figment of our statistical imaginations.... a blue-ribbon panel of economists headed by Michael Boskin of Stanford declared that the Consumer Price Index [C.P.I.] had been systematically overstating inflation, probably by more than 1 percent per year for the last two decades, mainly failing to take account of changes in the patterns of consumption and improvements in product quality.... ...The Boskin report, in particular, is not an official document -- it will be quite a while before the Government actually issues a revised C.P.I., and the eventual revision may be smaller than Boskin and his colleagues propose. Still, the general outline of the resolution is pretty clear. When all the revisions are taken into account, productivity growth will probably look somewhat higher than it did before, because some of the revisions being proposed to the way we measure consumer prices will also affect the way we calculate growth. But the rate of growth of real wages will look much higher -- and so it will now be roughly in line with productivity, which will therefore reconcile numbers on productivity and wages with data that show a roughly unchanged distribution of income between capital and labor. In other words, the whole story about workers not sharing in productivity gains will turn out to have been based on a statistical illusion. It is important not to go overboard on this point. There are real problems in America, and our previous concerns were by no means pure hypochondria. For one thing, it remains true that the rate of economic progress over the past 25 years has been much slower than it was in the previous 25. Even if Boskin's numbers are right, the income of the median family -- which officially has experienced virtually no gain since 1973 -- has risen by only about 35 percent over the past 25 years, compared with 100 percent over the previous 25. Furthermore, it is quite likely that if we "Boskinized" the old data -- that is, if we tried to adjust the C.P.I. for the 50's and 60's to take account of changing consumption patterns and rising product quality -- we would find that official numbers understated the rate of progress just as much if not more than they did in recent decades.... ...Moreover, while workers as a group have shared fully in national productivity gains, they have not done so equally. The overwhelming evidence of a huge increase in income inequality in America has nothing to do with price indexes and is therefore unaffected by recent statistical revelations. It is still true that families in the bottom fifth, who had 5.4 percent of total income in 1970, had only 4.2 percent in 1994; and that over the same period the share of the top 5 percent went from 15.6 to 20.1. And it is still true that corporate C.E.O.'s, who used to make about 35 times as much as their employees, now make 120 times as much or more.... ...While these are real and serious problems, however, one thing is now clear: the truth about what is happening in America is more subtle than the simplistic morality play about greedy capitalists and oppressed workers that so many would- be sophisticates accepted only a few months ago. There was little excuse for buying into that simplistic view then; there is no excuse now.... The author mentions the figures in paragraph six (lines 67?2) in order to show that:

  A. the total productivity of America has not seen a significant increase since the 1970's.
  B. each American worker's productivity is directly proportional to overall national productivity gains.
  C. the income inequality in America is a problem that is not eliminated by revision of the price index.
  D. Boskin's report is unable to explain the discrepancy between productivity growth and wage increases.
  C. the income inequality in America is a problem that is not eliminated by revision of the price index.

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  Explanation/Reference:

  Immediately before citing the numbers in lines 68?2, the author makes the point that the "evidence of a huge increase in income inequality in America has nothing to do with price indexes..." In other words, regardless of the merit or flaws of

  the Boskin study, income inequality is still a problem. The figures cited are used to illustrate this point.

  All the other choices do not pertain to the statistics quoted.

• Question 638:

  If tension in the string remains constant but the diameter of the sitting is doubled, what will be the effect on speed of transverse waves in the string?

  A. It remains constant.
  B. It becomes double.
  C. It becomes half.
  D. It decreases four times.
  C. It becomes half.

• Question 639:

  ...[TV Guide's] immediate concern was the television quiz show scandal, which had reached its climax two weeks earlier when Charles Van Doren, the appealing young man who'd taught viewers the value of learning while winning big on MCA's Twenty-one, stood before a House committee and admitted he was a fraud. But the issue went well beyond rigged quiz shows. The charge was that through their stranglehold on talent, MCA and William Morris monopolized the medium to the detriment of their clients, the industry, and the public at large. This was why the Justice Department had launched a secret investigation of both agencies more than two years before. The Morris Agency had started the quiz show vogue in 1955, when it packaged The $64,000 Question for Revlon and sold it to CBS. While the show won praise for its "educational" nature, the real source of its appeal was in its crapshoot format -- the idea that once contestants' winnings hit the $32,000 mark, they had to decide whether to go double or nothing on the final, $64,000 question, or play it safe and go home. The response was tremendous. Within weeks, the show knocked I Love Lucy out of the number-one slot in the ratings. Casinos in Vegas emptied out when it went on the air. Bookies took odds on whether the first contestant to go for the big one -- a marine captain whose specialty was cooking -- would get the answer right. (He did.) Revlon sold so much Living Lipstick that its factory was unable to meet the demand. The $64,000 Question quickly inspired imitators, among them an MCA package called Twenty-one. Based on the card game, more or less, Twenty-one was a dismal failure at first. "Do whatever you have to do," the sponsor ordered angrily, so the producers put the fix in. In December 1956, when Charles Van Doren, a boyishly attractive English instructor at Columbia University, beat Herb Stempel, a short, squat, nerdy grad at City College, Van Doren became the first intellectual hero of the television age. Honors and acclaim poured in -- the covers of Time, letters by the hundreds, offers of movie roles and tenured professorships and a regular guest spot on The Today Show. But Herb Stempel didn't like being told to lose, especially to some Ivy League snot. He went to the press. The DA's office started to investigate. The walls began to close in. Meanwhile, the show's producers agreed to sell the rights to NBC for $2 million. One of them started to feel queasy about selling the show without letting the network know the score, so he went to Sonny Werblin, MCA's top man in New York, and asked his advice. Werblin, the man behind such hits as The Ed Sullivan Show and The Jackie Gleason Show, ran the television department as if it were a football team coached by Attila the Hun. "Dan," he asked the producer, "have I ever asked you whether the show was rigged?" No, he hadn't. "And has NBC ever asked you whether the show is rigged?" No, they hadn't either. "Well," Werblin concluded, "the reason that none of us has asked is because we don't want to know." And with good reason. Not only was Twenty-one an MCA package and Van Doren himself an MCA client; Werblin had a special relationship with NBC's president, Robert Kintner. Kintner had been president of ABC until...ABC's chairman forced him out in his determination to move the network out of third place. MCA used its influence to place him at NBC, where he proved an extremely pliant customer. In the spring of 1957, when the networks were putting together their schedules for the next season, Werblin went to a meeting of NBC programming executives led by Kintner and his boss, RCA chairman Robert Sarnoff. "Sonny, look at the schedule for next season," Kintner said when he walked in, "here are the empty slots, you fill them."

  Suppose that the contestants on the television game shows mentioned in the passage had not been supplied with answers. Which of the following conclusions would most likely be correct?

  A. The Justice Department would have ended its investigation into the television production industry.
  B. Herb Stempel would have continued as champion on Twenty-one.
  C. The ABC chairman would not have removed Robert Kintner from the presidency.
  D. Herb Stempel would not have gone to the press shortly after December 1956.
  D. Herb Stempel would not have gone to the press shortly after December 1956.

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  Explanation/Reference:

  It was stated in the passage that the reason why Stempel went to the press was because he did not like being the "predetermined loser." If the contestants had been competing fairly, therefore, he would not have gone to the press. Choice A is incorrect because even though the rigging of game shows was what precipitated intense investigation, it is stated in paragraph 1 that a secret investigation had been launched more than two years before because of suspected monopolizing activity within the industry. Choice B is not the correct choice because Stempel may have lost fairly as well. Nothing in the passage indicates that his continued winning is necessarily a likely outcome. Choice C is incorrect because there is no indication at all that the firing of Kintner is related to the quiz show scandal.

• Question 640:

  The periodic beating of the heart is controlled by electrical impulses that originate within the cardiac muscle itself. These pulses travel to the sinoatrial node and from there to the atria and the ventricles, causing the cardiac muscles to contract. If a current of a few hundred milliamperes passes through the heart, it will interfere with this natural system, and may cause the heart to beat erratically. This condition is known as ventricular fibrillation, and is life-threatening. If, however, a larger current of about 5 to 6 amps is passed through the heart, a sustained ventricular contraction will occur. The cardiac muscle cannot relax, and the heart stops beating. If at this point the muscle is allowed to relax, a regular heartbeat will usually resume.

  The large current required to stop the heart is supplied by a device known as a defibrillator. A schematic diagram of a defibrillator is shown below. This device is essentially a "heavy-duty" capacitor capable of storing large amounts of energy. To charge the capacitor quickly (in 1 to 3 seconds), a large DC voltage must be applied to the plates of the capacitor. This is achieved using a step-up transformer, which creates an output voltage that is much larger than the input voltage. The transformer used in this defibrillator has a step-up ratio of 1:50.

  

  The AC voltage that is obtained from the transformer must then be converted to DC voltage in order to charge the capacitor. This is accomplished using a diode, which allows current flow in one direction only. Once the capacitor is fully charged, the charge remains stored until the switch is moved to position B and the plates are placed on the patient's chest. To cut down the resistance between the patient's body and the defibrillator, the electrodes are covered with a wetting gel before use. Care must be taken to insure that the patient is not in electrical contact with the ground while the defibrillator is in use.

  The resistance between the two electrodes when placed apart on the patient's chest is 1,000 when wetting gel is used. What is the initial current through the patient's heart, assuming that all the current takes this path?

  A. 0.16 A
  B. 4 A
  C. 6.25 A
  D. 8 A
  D. 8 A

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  Explanation/Reference:

  This question asks you to calculate the initial current through the patient, and this can be done by using Ohm's law which states that the current is equal to the voltage divided by the resistance. We know that the resistance across the two electrodes is 1000 ohms when a wetting gel is applied, but as in the previous question we do not have a value for the initial voltage. This be calculated as well. We know that the transformer increases the input voltage by a factor of 50, and since the input voltage is 160 volts, the output voltage will be 8000 volts. This voltage charges the capacitor only, so the voltage across the capacitor when fully charged will be 8000 volts. By substituting the values for the resistance and the voltage into Ohm's law, we find that the initial current flowing through the patient is 8000 divided by 1000, or 8 amps which is choice D.