Introduction / Context:
Understanding SI-derived units and their practical applications is essential in basic physics and electronics. “Hertz” (Hz) is the unit of frequency, meaning cycles per second. “Kilohertz” (kHz) equals 10^3 hertz. In communications and radio engineering, kHz commonly specifies the frequency of electromagnetic waves, such as AM broadcast bands and various signaling systems.
Given Data / Assumptions:
- Base unit: hertz (frequency = cycles per second).
- Scale: kilo- = 10^3 (1,000).
- Context examples: radio carriers, audio sampling lower ranges, and ultrasonic boundaries.
Concept / Approach:
Frequency describes how often a periodic event repeats per unit time. While many phenomena have frequencies (sound, mechanical oscillations), the option that most accurately links “kilohertz” in common usage to a measurable domain is “electromagnetic radio wave frequencies.” Other listed electrical quantities—power, voltage, resistance—are measured in watts, volts, and ohms respectively and do not use hertz as their unit.
Step-by-Step Solution:
1) Decode units: Hz = 1/s; kHz = 1,000/s.2) Identify domain: radio communications typically specify carriers in kHz or MHz.3) Match to options: “electromagnetic radio wave frequencies” is correct.4) Exclude mismatched quantities: watts, volts, ohms involve different dimensions.
Verification / Alternative check:
Example: An AM station at 810 kHz broadcasts with a carrier whose frequency is 810,000 cycles per second—textbook use of kHz for EM waves.
Why Other Options Are Wrong:
power used by a current of one ampere: Power is volts * amperes, measured in watts.voltage: Measured in volts; not a rate.electric resistance: Measured in ohms; not a rate.
Common Pitfalls:
Mixing up acoustic frequency with electrical quantities. While sound has frequency in hertz, the best option provided explicitly mentions radio waves, aligning with standard phrasing for kHz.
Final Answer:
electromagnetic radio wave frequencies
Discussion & Comments