Dear sir i want to ask one thing only if t is an instantaneous value or voltage is a function of t means in 0.02 second which is a time period of sin waveform voltage value start from 0 and goes to its peak value and then become zero then again goes in negative peak before become to zero this all process occur so fast that we cant see with our eye??? m i right sir???
Dear sir i want to ask one thing only if t is an instantaneous value or voltage is a function of t means in 0.02 second which is a time period of sin waveform voltage value start from 0 and goes to its peak value and then become zero then again goes in negative peak before become to zero this all process occur so fast that we cant see with our eye??? m i right sir???
First of all, it depends on what you're looking at. If it's a wire impinged upon by the sinewave voltage or a bunch of electronic components similarly impinged (none of which convert the electrical energy to light) then you aren't going to "see" anything no matter what the frequency is.
If you are looking at something like a light whose brightness is being modulated by the sinewave voltage, then if the frequency is below around 70Hz, you are likely to begin to see it (especially in your peripheral vision). And, below around 30 Hz you're even more likely to see it. At 10 Hz and below, it's pretty much a certainty that anyone with vision will see the light's intensity fluctuate up and down.
If it is a scope you're looking at, then only the capture rate of the scope is an issue. Though, what you will be "seeing" there is a history of the sinewave event.
As steve says you are not going to see anything as the time to complete 1 cycle at 60 hertz is 16.67millisecs or at 50 hertz it would be 20 millisec. So at 50 hertz - after 5 millisec the voltage will hit a positive peak, after 10 millisec the voltage would be zero and at 15 millisec the voltage would be at the negative peak and at 20 millisec the voltage is back to zero and the whole thing repeats it self. as steve said as the frequency gets lower so can start to see the strobing effect. If you got the frequency low enough you could actually what is going thru the cycle
thank you so much now can you please tell me one thing what is a difference between Dc offset value and avg value ??? because avg value of full wave rectification is like 2vm/pi and as said Calinoaia Valentin V=Vm sin(wt) ) this V is called DC offset value???
DC offset value is only in reference to the sinewave - when a sinewave has an average value then it is called dc offset. The average value of a sinewave is zero when when it is not then it is said to have a dc offset
Another term for "DC offset" is "DC component". If the sinewave swings just as much above zero volts as it does below zero volts, then it has no DC component (or DC offset). It's purely AC. But, if the magnitude of the sum of the positive portion of the wave is different than the magnitude of the sum of the negative portion (i.e. take the "average" of the waves instantaneous levels over one cycle), then the wave is "AC with a DC component" or "AC with a DC offset".
This occurs when a DC voltage is added to an AC voltage.
BUT, the "average" spoken of , above, is the _algebraic average_. The the _average value_ that you asked about, is different. That is the average of the _absolute value_ of the instantaneous levels over one cycle. For a sinewave it's 0.637 times the _peak value_.
A sine wave or sinusoid is a mathematical curve that describes a smooth periodic oscillation. A sine wave is a continuous wave. It is named after the function sine, of which it is the graph. It occurs often in pure and applied mathematics, as well as physics, engineering, signal processing and many other fields.
✨ The equation v = Vm sin(ωt) describes a sinusoidal waveform where v(t) is the instantaneous voltage at time t. Vm represents the peak voltage amplitude, ω (omega) is the angular frequency defined as 2πf with f being the frequency in Hertz, and t is the instantaneous time variable in seconds. The sine wave voltage varies periodically, starting from zero, reaching positive and negative peaks within one period (T = 1/f). The waveform can be expressed as v(t) to emphasize its time dependence. A DC offset (or DC component) is a constant voltage added to the sine wave, shifting its average value away from zero; without this offset, the average value of a pure sine wave is zero. The difference between DC offset and average value is clarified: DC offset refers to the algebraic average of the waveform over a cycle, while the average value often refers to the average of the absolute values of the waveform. The RMS (root mean square) value and peak-to-peak voltage are related but distinct parameters. The discussion also explains that at typical power frequencies (50-60 Hz), the rapid voltage changes in the sine wave are too fast to be perceived visually, though at lower frequencies, modulation effects such as flickering can be observed. Additional references and explanations on waveform characteristics and definitions were provided.
TL;DR: v(t)=Vm·sin(ωt) models a sine voltage. Concrete stat: at 50 Hz, one cycle lasts 20 ms. Expert quote: "at 50 hertz it would be 20 millisec." [Elektroda, David Adams, post #21662739]
Why it matters: This FAQ helps beginners interpret sinewave equations, pick the right values, and avoid DC/RMS confusion in labs and exams, especially for AC mains and bench signals.
t is instantaneous time in seconds. v or v(t) is the instantaneous voltage value at that time. v changes as t changes, following the sine. Write it explicitly as v(t) to emphasize that voltage depends on time. [Elektroda, David Adams, post #21662735]
Is t the time period T of the signal?
No. t is a running time variable. The time period T is one full cycle’s duration and equals 1/f. In contrast, t can be any moment you evaluate the waveform. Confusing t with T leads to wrong phase and amplitude results. [Elektroda, Steve Lawson, post #21662734]
What is ω and how does it relate to frequency f?
ω is angular frequency in radians per second. It equals 2πf, where f is in hertz. Substitute ω=2πf into v(t)=Vm·sin(ωt) whenever you know f instead of ω. [Elektroda, David Adams, post #21662735]
How do I compute the instantaneous voltage at a specific time?
Use v(t)=Vm·sin(2πft). Example: Vm=10 V, f=50 Hz, t=5 ms → v=10·sin(2π·50·0.005)=10·sin(π/2)=10 V. Pro tip: express t in seconds. [Elektroda, David Adams, post #21662735]
What’s the difference between DC offset and average value?
DC offset (DC component) is the algebraic average of the waveform over a cycle. A pure sine’s algebraic average is zero. The average value often cited in rectifier contexts means the average of the absolute value; for a sine it is ≈0.637·Vm. [Elektroda, Steve Lawson, post #21662742]
How is RMS different from DC offset or average value?
RMS measures heating-equivalent value. For a pure sine, Vrms≈0.707·Vm. DC offset is a constant added to the waveform. The rectified average (≈0.637·Vm) characterizes rectifier outputs, not the AC’s heating effect. [Elektroda, Steve Lawson, post #21662742]
What does peak-to-peak (Vp‑p) mean versus Vm?
Vm (often Vp) is the maximum excursion from zero. Peak‑to‑peak is the total swing, Vp‑p=2·Vm. If Vm=5 V, Vp‑p=10 V. Many oscilloscopes display Vp‑p by default, so convert as needed. [Elektroda, David Adams, post #21662735]
What happens over one 50 Hz cycle in time?
At 50 Hz, T=20 ms. Typical landmarks: 0 ms→0 V crossing, 5 ms→positive peak, 10 ms→0 V, 15 ms→negative peak, 20 ms→back to 0 V. Then it repeats. This timeline helps when checking phase on scopes. [Elektroda, David Adams, post #21662739]
Why can’t I see AC voltage changing with my eyes?
You can’t see electrical changes in wires. With a lamp driven by AC, flicker becomes noticeable below about 70 Hz, obvious near 30 Hz, and clear near 10 Hz. "What you see on a scope is the history of the event." [Elektroda, Steve Lawson, post #21662738]
How do I add a DC offset to a sine wave in the equation?
Include a constant term: v(t)=Vdc+Vm·sin(ωt). Vdc shifts the waveform up or down without changing its frequency or peak‑to‑peak. Zero offset means the positive and negative halves are symmetric. [Elektroda, David Adams, post #21662735]
Is V in v=Vm·sin(ωt) the DC offset?
No. In this equation, v (lowercase) is instantaneous voltage. If there is a DC offset, write v(t)=Vdc+Vm·sin(ωt). Using just v=Vm·sin(ωt) implies zero DC offset. [Elektroda, David Adams, post #21662735]
How can I tell if a waveform has a DC component?
Compute its algebraic average over one period. If the average is not zero, the waveform has a DC component (offset). A pure sine centered on zero has none. [Elektroda, Steve Lawson, post #21662742]
Can an oscilloscope show these relationships clearly?
Yes. Timebase shows period T; cursors can measure 5 ms, 10 ms, etc., at 50 Hz. Vertical scaling shows Vm or Vp‑p so you can infer Vrms or average if the scope lacks math functions. [Elektroda, David Adams, post #21662739]
Do people often confuse t with T in practice? What’s the risk?
Yes. Treating t as the fixed period T misplaces phase and yields wrong instantaneous values. Always keep t as a variable and use T=1/f only for cycle length. [Elektroda, Steve Lawson, post #21662734]
