passage 4

The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy (5) used, thus apparently contradicting the principle of energy conservation. Heat pumps circulate a fluid refrigerant that cycles alternatively from its liquid phase to its vapor phase in a closed loop. The refrigerant, (10) starting as a low-temperature, low-pressure vapor, enters a compressor driven by an electric motor. The refrigerant leaves the compressor as a hot, dense vapor and flows through a heat exchanger called the condenser, which transfers heat from the (15) refrigerant to a body of air. Now the refrigerant, as a high-pressure, cooled liquid, confronts a flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and par- tially vaporizes, becoming chilled. It then passes (20) through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing the temperature of this second body of air. Of the two heat exchangers, one is located inside, and the other one outside the house, so (25) each is in contact with a different body of air: room air and outside air, respectively. The flow direction of refrigerant through a heat pump is controlled by valves. When the refrigerant flow is reversed, the heat exchangers switch func- (30) tion. This flow-reversal capability allows heat pumps either to heat or cool room air. Now, if under certain conditions a heat pump puts out more thermal energy than it consumes in electrical energy, has the law of energy conserva- (35) tion been challenged? No, not even remotely: the additional input of thermal energy into the circu- lating refrigerant via the evaporator accounts for the difference in the energy equation. Unfortunately, there is one real problem. The (40) heating capacity of a heat pump decreases as the outdoor temperature falls. The drop in capacity is caused by the lessening amount of refrigerant mass moved through the compressor at one time. The heating capacity is proportional to this mass flow (45) rate: the less the mass of refrigerant being com- pressed, the less the thermal load it can transfer through the heat-pump cycle. The volume flow rate of refrigerant vapor through the single-speed rotary compressor used in heat pumps is approxi- (50) mately constant. But cold refrigerant vapor enter- ing a compressor is at lower pressure than warmer vapor. Therefore, the mass of cold refrigerant- and thus the thermal energy it carries-is less than if the refrigerant vapor were warmer before com- (55) pression. Here, then, lies a genuine drawback of heat pumps: in extremely cold climates-where the most heat is needed-heat pumps are least able to supply enough heat. 1. The primary purpose of the passage is to (A) explain the differences in the working of a heat pump when the outdoor temperature changes (B) contrast the heating and the cooling modes of heat pumps (C) describe heat pumps, their use, and factors affecting their use (D) advocate the more widespread use of heat pumps (E) expose extravagant claims about heat pumps as false 2. The author resolves the question of whether heat pumps run counter to the principle of energy conservation by (A) carefully qualifying the meaning of that principle (B) pointing out a factual error in the statement that gives rise to this question (C) supplying additional relevant facts (D) denying the relevance of that principle to heat pumps (E) explaining that heat pumps can cool, as well as heat, room air 3. It can be inferred from the passage that, in the course of a heating season, the heating capacity of a heat pump is greatest when (A) heating is least essential (B) electricity rates are lowest (C) its compressor runs the fastest (D) outdoor temperatures hold steady (E) the heating demand surges 4. If the author's assessment of the use of heat pumps(lines 1-6) is correct, which of the following best expresses the lesson that advertisers should learn from this case? (A) Do not make exaggerated claims about the products you are trying to promote. (B) Focus your advertising campaign on vague analogies and veiled implications instead of on facts. (C) Do not use facts in your advertising that willstrain the prospective client's ability to believe. (D) Do not assume in your advertising that the prospective clients know even the most elementary scientific principles. (E) Concentrate your advertising firmly on financially relevant issues such as price discounts and efficiency of operation. 5. The passage suggests that heat pumps would be used more widely if (A) they could also be used as air conditioners (B) they could be moved around to supply heat where it is most needed (C) their heat output could be thermo-statically controlled (D) models with truly superior cooling capacity were advertised more effectively (E) people appreciated the role of the evaporator in the energy equation 6. According to the passage, the role of the flow restriction (lines 16-17) in a heat pump is to (A) measure accurately the flow rate of the refrigerant mass at that point (B) compress and heat the refrigerant vapor (C) bring about the evaporation and cooling of refrigerant (D) exchange heat between the refrigerant and the air at that point (E) reverse the direction of refrigerant flow when needed 7. The author regards the notion that heat pumps have a genuine drawback as a (A) cause for regret (B) sign of premature defeatism (C) welcome challenge (D) case of sloppy thinking (E) focus for an educational campaign Passage 2 Islamic law is a particularly instructive example of "sacred law." Islamic law is a phenomenon so different from all other forms of law.not withstanding, of course, a considerable and inevitable number of coincidences with one or the other of them as far as subject matter and positive enactment are concerned-that its study is indispensable in order to appreciate adequately the full range of possible legal phenomena. Even the two other representatives of sacred law that are historically and geographically nearest to it, Jewish law and Roman Catholic canon law, are perceptibly different. Both Jewish law and canon law are more uniform than Islamic law. Though historically there is a discernible break between Jewish law of the sovereign state of ancient Israel and of the Diaspora (the dispersion of Jewish people after the conquest of Israel), the spirit of the legal matter in later parts of the Old Testament is very close to that of the Talmud, one of the primary codifications of Jewish law in the Diaspora. Islam, on the other hand, represented a radical breakaway from the Arab paganism that preceded it; Islamic law is the result of an examination, from a religious angle, of legal subject matter that was far from uniform, comprising as it did the various components of the laws of pre-Islamic Arabia and numerous legal Islamic law is the result of an examination, from a religious angle, of legal subject matter that was far from uniform, comprising as it did the various components of the laws of pre-Islamic Arabia and numerous legal elements taken over from the non-Arab peoples of the conquered territories. All this was unified by being subjected to the same kind of religious scrutiny, the impact of which varied greatly, being almost nonexistent in some fields, and in others originating novel institutions. This central duality of legal subject matter and religious norm is additional to the variety of legal, ethical, and ritual rules that is typical of sacred law. In its relation to the secular state, Islamic law differed from both Jewish and canon law. Jewish law was buttressed by the cohesion of the community, reinforced by pressure from outside; its rules are the direct expression of this feeling of cohesion, tending toward the accommodation of dissent. Canon and Is-lamic law, on the contrary, were dominated by the dualism of religion and state, where the state was not, in contrast with Judaism, an alien power but the political expression of the same religion. But the conflict between state and religion took different forms; in Christianity it appeared as the struggle for political power on the part of a tightly organized ecclesiastical hierarchy, and canon law was one of its political weapons. Islamic in contrast with Judaism, an alien power but the political expression of the same religion. But the conflict between state and religion took different forms; in Christianity it appeared as the struggle for political power on the part of a tightly organized ecc-lesiastical hierarchy, and canon law was one of itspolitical weapons. Islamic law, on the other hand, was never supported by an organized institution; consequently, there never developed an overt trial of strength. There merely existed discordance between application of the sacred law and many of the regulations framed by Islamic states; this antagonism varied according to place and time. 1. The author's purpose in comparing Islamic law to Jewish law and canon law is most probably to (A)contend that traditional legal subject matter does not play a large role in Ialamic law (B)support his argument that Islamic law is a unique kind of legal phenomenon (C)emphasize the variety of forms that can all be considered sacred law (D)provide an example of how he believes comparative institutional study should be undertaken (E)argue that geographical and historical proximity does not necessarily lead to parallel institutional development KEYS: Passage 1: CCACE CA Passage 2: B