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What energy conversion occurs in a solar cell?
- A. Electrical energy to light energy
- B. Chemical energy to electrical energy
- C. Solar energy to thermal energy
- D. Solar energy to electrical energy
Correct Answer: D
Rationale: Solar cells, also known as photovoltaic cells, convert solar energy from sunlight directly into electrical energy through a process called the photovoltaic effect. This process involves the absorption of photons from sunlight, which then generate an electric current. Choice A is incorrect because solar cells do not convert electrical energy into light energy. Choice B is incorrect as solar cells do not involve chemical energy conversion. Choice C is incorrect because solar cells do not primarily convert solar energy into thermal energy. Therefore, the correct answer is D) Solar energy to electrical energy.
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Which of the following accurately describes saltatory conduction?
- A. It is faster than normal nerve conduction
- B. It occurs from one node of Ranvier to the next
- C. It only occurs in myelinated neurons
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, 'All of the above.' Saltatory conduction is faster than normal nerve conduction, occurs from one node of Ranvier to the next, and is exclusive to myelinated neurons. This form of conduction allows for the rapid transmission of nerve impulses by the action potential jumping between the nodes of Ranvier in myelinated neurons, enhancing the efficiency of signal propagation along the axon. Choice A is correct as saltatory conduction is indeed faster than normal conduction. Choice B is accurate as it describes the mechanism of conduction 'jumping' from one node of Ranvier to the next. Choice C is correct because saltatory conduction occurs specifically in myelinated neurons where the myelin sheath insulates the axon except at the nodes of Ranvier, facilitating faster transmission of nerve impulses.
Which element is used in jewelry due to its malleability and resistance to tarnish?
- A. Iron
- B. Copper
- C. Gold
- D. Silver
Correct Answer: C
Rationale: Gold is the correct answer. Gold is a popular choice for jewelry due to its exceptional malleability, allowing it to be easily shaped into intricate designs. Moreover, gold is resistant to tarnish, ensuring the jewelry retains its beauty over time. Iron is not commonly used in jewelry due to its susceptibility to rusting. Copper is also not as popular in jewelry making as gold due to its tendency to tarnish and cause skin discoloration. While silver is used in jewelry, it is more prone to tarnish compared to gold, making it less ideal for long-lasting pieces.
During a scientific investigation, what is intentionally changed or manipulated?
- A. The dependent variable.
- B. The control.
- C. The hypothesis.
- D. The independent variable.
Correct Answer: D
Rationale: During a scientific investigation, the independent variable is intentionally changed or manipulated by the researcher to observe its impact or effect on the dependent variable. The independent variable is the one being tested or studied to see how it influences the dependent variable. In contrast, the dependent variable is the outcome or response that is measured in an experiment and is expected to change as a result of the manipulation of the independent variable. Choices A, B, and C are not directly altered during a scientific investigation but play different roles in the research process. Therefore, the correct answer is D - the independent variable.
Which organelle is responsible for controlling the activities of the cell?
- A. Golgi apparatus
- B. Mitochondria
- C. Nucleus
- D. Ribosomes
Correct Answer: C
Rationale: The nucleus is the organelle responsible for controlling the activities of the cell. It contains the cell's genetic material (DNA) and serves as the command center of the cell, regulating gene expression and directing cellular activities. The nucleus plays a crucial role in cell growth, metabolism, and reproduction. While the Golgi apparatus is involved in processing and packaging proteins, the mitochondria are responsible for producing energy in the form of ATP, and ribosomes are involved in protein synthesis, none of these organelles have the primary function of controlling the activities of the cell like the nucleus does. Therefore, the correct answer is the nucleus.
Which hormone primarily triggers ovulation in the female menstrual cycle?
- A. Estrogen
- B. Progesterone
- C. Luteinizing hormone (LH)
- D. Follicle-stimulating hormone (FSH)
Correct Answer: C
Rationale: Luteinizing hormone (LH) is the hormone primarily responsible for triggering ovulation in the female menstrual cycle. LH surge occurs around the middle of the menstrual cycle, causing the mature follicle to release an egg from the ovary. Estrogen and progesterone play crucial roles in regulating the menstrual cycle and preparing the endometrium for potential implantation of a fertilized egg, but they do not trigger ovulation directly. Follicle-stimulating hormone (FSH) is essential for the development of ovarian follicles but is not the primary hormone responsible for ovulation. Therefore, the correct answer is Luteinizing hormone (LH) as it directly initiates the release of the egg during ovulation.