Why on a oscilloscope does a.c current have a sine wave, whereas a d.c

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Discussion Overview

The discussion revolves around the observation of alternating current (AC) and direct current (DC) waveforms on an oscilloscope, specifically why AC appears as a sine wave while DC appears as a straight line. The scope includes explanations aimed at beginners in physics, particularly those in early stages of their studies.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant notes that the x-axis on the oscilloscope represents time and the y-axis represents voltage or current, explaining that DC is constant over time, resulting in a straight line.
  • Another participant states that AC, which stands for alternating current, is characterized by the current moving back and forth, thus creating a sine wave.
  • A participant provides a resource link to an Oscilloscope Primer from Tektronix, suggesting it may help the original poster understand the topic better.

Areas of Agreement / Disagreement

Participants generally agree on the basic definitions and characteristics of AC and DC as observed on an oscilloscope, but the discussion remains open for further clarification and exploration of the topic.

Contextual Notes

The discussion does not delve into the underlying physics of why AC takes the form of a sine wave or the implications of these waveforms in practical applications, leaving these aspects unexplored.

Sofie1990
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Why on a oscilloscope does a.c current have a sine wave, whereas a d.c current is just a straight line. I've tried to look it up, but the explanations on the internet are a bit to complex for me to understand as i am only in my first year of alevel. If anyone could explain this to me, as simply as possible, i would be very grateful. Cheers
 
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The x-axis on the scope is time, the y-axis is your voltage/current. Since DC is constant in time, it's a straight line. The trace of an AC signal that is monofrequency is a sine wave in time.
 


Simply put: a.c. stands for alternating current, hence the current is constantly going back and forth, creating a wave. d.c. stands for direct current, meaning the current is traveling in a constant direction so there is just a line.
 


Sofie1990 said:
Why on a oscilloscope does a.c current have a sine wave, whereas a d.c current is just a straight line. I've tried to look it up, but the explanations on the internet are a bit to complex for me to understand as i am only in my first year of alevel. If anyone could explain this to me, as simply as possible, i would be very grateful. Cheers

Welcome to the PF.

In addition to the answers you've already gotten, you might want to check out the Oscilloscope Primer from Tektronix:

http://www.tek.com/learning/oscilloscope-tutorial

The link to it is the first in the list on that page. You will need to make a free account at the Tek website first, unfortunately, but the Primer should be worth the extra time that takes. The Primer starts off with the basics that you are interested in, and then there is plenty more information for whenever you are ready to study it.
 

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