HESI A2
HESI A2 Physics Practice Test
1. When analyzing a power plant, which of the following is NOT considered a part of the system?
- A. The fuel being burned.
- B. The working fluid (e.g., steam or water).
- C. The turbine that generates electricity.
- D. The surrounding air.
Correct answer: D
Rationale: In a power plant system, the components directly involved in the energy conversion process are considered part of the system. The fuel being burned provides the heat source, the working fluid transfers this heat energy, and the turbine converts it into mechanical energy to generate electricity. The surrounding air, while it may interact with the system, is not a component that directly participates in the energy conversion process within the power plant system. Therefore, the correct answer is D - The surrounding air. Choices A, B, and C are essential components of a power plant system as they play direct roles in the energy conversion process, unlike the surrounding air.
2. In fluid dynamics, the continuity equation, a fundamental principle, expresses the conservation of:
- A. Momentum
- B. Mass
- C. Energy
- D. Angular momentum
Correct answer: B
Rationale: The continuity equation in fluid dynamics is a statement of the conservation of mass, making choice B the correct answer. It states that the mass entering a system must equal the mass leaving the system, assuming no mass is created or destroyed within the system. Conservation of momentum (choice A) is related to Newton's laws of motion and is not directly expressed by the continuity equation. Conservation of energy (choice C) involves different principles like the first law of thermodynamics and is not the focus of the continuity equation. Angular momentum (choice D) is also a different concept related to rotational motion and not described by the continuity equation.
3. Household alternating current typically has a frequency of 60 Hz. Which statement is true?
- A. The circuit is suitable for lighting 60-watt bulbs.
- B. Circuits in the home may carry a current of 60 amperes.
- C. The expected voltage drop is 60 volts per meter.
- D. Electrons complete a cycle 60 times per second.
Correct answer: D
Rationale: The correct answer is D. Electrons complete a cycle 60 times per second when the frequency of the current is 60 Hz. This frequency indicates that the current changes direction 60 times per second, causing the electrons to complete a full cycle back and forth through the circuit at the same rate. Choice A is incorrect because the power rating of a bulb (in watts) is not directly related to the frequency of the current. Choice B is incorrect as typical household circuits do not carry currents as high as 60 amperes. Choice C is incorrect as the expected voltage drop is not measured in volts per meter for household alternating current circuits.
4. When a dielectric material is inserted between the plates of a charged capacitor, what will happen to the capacitance?
- A. Increase
- B. Decrease
- C. Remain the same
- D. Become unpredictable
Correct answer: A
Rationale: When a dielectric material is inserted between the plates of a charged capacitor, the capacitance will increase. This is because the presence of a dielectric material reduces the electric field between the plates, allowing more charge to be stored for a given voltage, thus increasing the capacitance. Choice B is incorrect because adding a dielectric material increases capacitance. Choice C is incorrect because capacitance changes when a dielectric is added. Choice D is incorrect because the effect of a dielectric on capacitance is predictable.
5. A 3-volt flashlight uses a bulb with 60-ohm resistance. What current flows through the flashlight?
- A. o.05 amp
- B. o.5 amp
- C. 1.8 amp
- D. 18 amp
Correct answer: A
Rationale: : Using Ohm's Law, I = V / R: I = 3 / 60 = 0.05 amp. So, the correct current is 0.05 amp.
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