Answer the following question given this paragraph: Since eddy currents and magnetic damping occur only in conductors, recycling centers can use magnets to separate metals from other materials. Trash is dumped in batches down a ramp, beneath which lies a powerful magnet. Conductors in the trash are slowed by magnetic damping while nonmetals in the trash move on, separating from the metals. (See Figure 23.17. ) This works for all metals, not just ferromagnetic ones. A magnet can separate out the ferromagnetic materials alone by acting on stationary trash. Q: Since eddy currents and magnetic damping occur only in conductors, recycling centers can use these to separate metals from other materials? Choices: - particles - cranes - alloys - magnets A:
magnets
(Question)
Answer the following question given this paragraph: The substances that comprise heterogeneous mixtures can also be separated by physical means. We will discuss separation techniques in the following lesson. Q: The substances that comprise heterogeneous mixtures can also be separated by what means? Choices: - thermal - chemical - atmospheric - physical A:
(Answer)
physical
Ques: Answer the following question given this paragraph: 3. Electrical energy is the energy of moving electrons. Electrons flow through wires to create electric current. Q: Electrons flow through wires to create what? Choices: - electromagnetism - hydroelectric power - balanced reaction - electric current A:
Ans: electric current
(Q).
Answer the following question given this paragraph: Particles of a hypothetical ideal gas have no significant volume and do not attract or repel each other. In general, real gases approximate this behavior at relatively low pressures and high temperatures. However, at high pressures, the molecules of a gas are crowded closer together, and the amount of empty space between the molecules is reduced. At these higher pressures, the volume of the gas molecules themselves becomes appreciable relative to the total volume occupied by the gas (Figure 9.36). The gas therefore becomes less compressible at these high pressures, and although its volume continues to decrease with increasing pressure, this decrease is not proportional as predicted by Boyle's law. Q: At high pressures, how are the molecules of a gas crowded? Choices: - few together - further apart - small together - closer together A:
(A).
closer together
Ques:Answer the following question given this paragraph: Because the health of cells depends on maintaining the proper levels of cations in intracellular fluids, any change that affects the normal flux of metal ions across cell membranes could well cause an organism to die. Molecules that facilitate the transport of metal ions across membranes are generally called ionophores (ionplus phore from the Greek phorein, meaning "to carry"). Many ionophores are potent antibiotics that can kill or inhibit the growth of bacteria. An example isvalinomycin, a cyclic molecule with a central cavity lined with oxygen atoms (part (a) in Figure 21.14 "Valinomycin Is an Antibiotic That Functions Like an Ionophore") that is similar to the cavity of a crown ether (part (a) in Figure 13.7 "Crown Ethers and Cryptands"). Like a crown ether, valinomycin is highly selective: its affinity for K+ is about 1000 times greater than that for Na+. By increasing the flux of K+ ions into cells, valinomycin disrupts the normal K+ gradient across a cell membrane, thereby killing the cell (part (b) in Figure 21.14 "Valinomycin Is an Antibiotic That Functions Like an Ionophore"). Figure 21.14 Valinomycin Is an Antibiotic That Functions Like an Ionophore. Q: Why is it necessary to maintain proper levels of cations in intercellular fluids? Choices: - cell division - reverse homeostasis - for digestion - keep cells healthy A:

Ans:keep cells healthy
Answer the following question given this paragraph: The Dutch scientist Christiaan Huygens (16291695) developed a useful technique for determining in detail how and where waves propagate. Starting from some known position, Huygens's principle states that: Every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets. Figure 27.5 shows how Huygens's principle is applied. A wavefront is the long edge that moves, for example, the crest or the trough. Each point on the wavefront emits a semicircular wave that moves at the propagation speed v . These are drawn at a time t later, so that they have moved a distance s = vt . The new wavefront is a line tangent to the wavelets and is where we would expect the wave to be a time t later. Huygens's principle works for all types of waves, including water waves, sound waves, and light waves. We will find it useful not only in describing how light waves propagate, but also in explaining the laws of reflection and refraction. In addition, we will see that Huygens's principle tells us how and where light rays interfere. Q: Dutch scientist christiaan huygens' principle of what states that every point on a wavefront is a source of wavelets that spread out in the forward direction at the speed of the wave itself? Choices: - electromagnetic dynamics - energy propagation - wave dynamics - wave propagation A:
wave propagation