HESI Exams Quizlet Physics

Correct Answer: B

Rationale: The correct answer is B (15.625 cm). To calculate the image height using mirror formula (1/f = 1/v + 1/u), first find the object distance (u) which is -20 cm (since object is placed on the same side as focal point, it is negative). Then, solve for image distance (v) by substituting u and f values. Next, use magnification formula (m = -v/u) to find the magnification factor. Finally, multiply the object height by the magnification factor to get the image height, which is 15.625 cm. Choice A (30.5 cm) is incorrect as it is double the correct answer. Choice C (-15 cm) and choice D (-30.5 cm) are incorrect as the negative sign indicates an inverted image, but in this case, the image is upright.

Correct Answer: C

Rationale: The correct answer is C because reversible processes can be run in both directions with the same outcome, while irreversible processes cannot. In a reversible process, the system and surroundings can be restored to their original states after the process is reversed, maintaining equilibrium. This is not possible in irreversible processes, where energy dissipation and entropy generation lead to permanent changes. Choices A, B, and D are incorrect because reversible processes can involve heat transfer, do take time, and do not violate the first law of thermodynamics.

Correct Answer: A

Rationale: The correct answer is A: Q = cΔT. This equation represents the definition of specific heat capacity, where Q (heat transfer) is equal to the product of c (specific heat capacity) and ΔT (temperature change) for a unit mass of the material. This equation is derived from the formula for heat transfer, Q = mcΔT, by dividing both sides by mass 'm'. Therefore, the correct equation is Q = cΔT. Summary of other choices: B: Q = mcΔT - This is the formula for total heat transfer, not specific heat capacity. C: Q = c / mΔT - This equation does not accurately represent the relationship between specific heat capacity, heat transfer, temperature change, and mass. D: Q = ΔT / mc - This equation is not a correct representation of specific heat capacity and does not follow the standard formula.

Correct Answer: C

Rationale: The correct answer is C: Its density increases. When a junked car is compacted, its volume decreases while its mass remains constant. Density is calculated as mass divided by volume, so with a decrease in volume and constant mass, the density increases. Option A is incorrect because mass remains the same. Option B is incorrect as mass does not decrease. Option D is incorrect because density is directly related to mass and volume, and in this case, volume decreases while mass stays the same, resulting in increased density.

Correct Answer: B

Rationale: The correct answer is B: Permeability is preferred. High permeability in the core of an electromagnet enhances its magnetic field strength by allowing more magnetic flux to pass through, increasing the efficiency of the electromagnet. Resistivity (choice A) would hinder current flow, reducing magnetic field strength. Permittivity (choice C) is related to electric fields, not magnetic fields. Dielectric strength (choice D) is the ability of a material to withstand electric fields, not directly related to enhancing magnetic properties.