Final answer:
An oscilloscope is a device that gives a visual display of voltages, showing the electrical signal over time. Ohmmeters and ammeters are different tools used for measuring resistance and current, respectively, and must be used with an understanding of their impact on the circuit. The correct answer is A.
Step-by-step explanation:
A device that gives a visual display of voltages is known as an oscilloscope. An oscilloscope displays the electrical signal over time, allowing for the observation of varying voltage levels. When connected to a microphone, an oscilloscope can also show sound converted into an electrical signal. Ohmmeters, on the other hand, are used to measure resistance in an electrical component using Ohm's law, which states that the resistance (R) equals the voltage (V) divided by the current (I), or R = V/I. Unlike oscilloscopes, ohmmeters need to isolate the component from the circuit for accurate measurement.
Ammeters are instruments that measure the amount of current flowing through a device and must be connected in series with the device. An ammeter affects the circuit to some extent, which can lead to limited accuracy in measurement. This is also true for standard voltmeters, which can alter the voltage of the circuit they are measuring. Therefore, accurate measurements require careful consideration of how these instruments are connected to the circuit.