household alternating current typically has a frequency of 60 hz which statement is true

HESI A2

HESI A2 Physics Practice Test

1. 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.

2. Surface tension, γ, is a property of fluids arising from:

A. Intermolecular forces between fluid molecules
B. Gravitational attraction
C. Viscous dissipation
D. Pressure differentials within the fluid

Correct answer: A

Rationale: Surface tension, represented by symbol γ, is caused by the cohesive forces between molecules in a liquid. These intermolecular forces, such as Van der Waals forces, hydrogen bonding, and dipole-dipole interactions, create a 'skin' at the surface of the liquid, giving rise to the property of surface tension. Gravitational attraction, viscous dissipation, and pressure differentials within the fluid do not directly contribute to surface tension. Therefore, the correct answer is A.

3. An incandescent lamp consumes 60 Joules of energy per second. What is the power rating of this lamp?

A. 1 Watt (W)
B. 60 Watts (W)
C. 1/60 Joules
D. Impossible to determine without knowing the voltage

Correct answer: B

Rationale: Power is defined as energy consumed per unit time. If the lamp consumes 60 Joules of energy per second, the power rating is 60 Watts. Therefore, choice B is correct. Choice A ('1 Watt') is incorrect because the lamp consumes 60 Joules per second, not 1 Joule per second. Choice C ('1/60 Joules') is incorrect as it does not represent the power rating. Choice D ('Impossible to determine without knowing the voltage') is incorrect because power can be calculated using energy consumption per unit time without needing to know the voltage.

4. If a wave has a frequency of 60 hertz, which of the following is true?

A. It completes one cycle per minute.
B. It measures 60 m from crest to crest.
C. It completes 60 cycles per second.
D. It measures 60 m from crest to trough.

Correct answer: C

Rationale: The frequency of a wave is the number of cycles it completes in one second. A wave with a frequency of 60 hertz completes 60 cycles per second. Therefore, choice C is correct. Choice A is incorrect because a frequency of 60 hertz means 60 cycles per second, not per minute. Choice B is incorrect as the frequency of the wave does not determine the distance from crest to crest. Choice D is also incorrect as the frequency does not relate to the distance from crest to trough.

5. As a car is traveling on the highway, its speed drops from 60 mph to 30 mph. What happens to its kinetic energy?

A. Its energy is halved.
B. Its energy is doubled.
C. Its energy is quadrupled.
D. Its energy is divided by four.

Correct answer: A

Rationale: The correct answer is A. Kinetic energy is proportional to the square of the velocity. When the speed drops from 60 mph to 30 mph, the kinetic energy is halved. Choice B is incorrect because halving the speed results in halving the kinetic energy, not doubling it. Choice C is incorrect because quadrupling the kinetic energy would require increasing the speed fourfold, not halving it. Choice D is incorrect because dividing the energy by four would imply a different relationship between speed and kinetic energy, which is not the case.