Using Desmos to display a formula

Thread Starter

leejohnson222

Joined Jan 11, 2023
57
So i have been working on a formula which is Vs = 5sin (2pi f t - Pi/3)

Looking for the point in time that 3+V appears and plot a graph to show
F = 1mhz

the Answer i found was T = 2.68971 x10^-7

i am new to this graph software so i just want to get my head around it, i know Voltage is y and Time is x
any tips on how to get the correct set up, i think time would be in multiples of 10^-7 although i dont know how to set this.
 

WBahn

Joined Mar 31, 2012
29,979
I have no idea what Desmos is, so I can't help you there.

By 3+V, do you mean the time when the voltage exceeds 3 V?

Are you sure your frequency is 1 millihertz? Or did you intend it to be megahertz? Is so, there's a difference of nine orders of magnitude.

You REALLY need to start using and treating units properly.

Vs = 5 V · sin(2pi f t - Pi/3)
or
Vs = 5·sin(2pi f t - Pi/3) V

ASIDE: The 2pi actually has units of radians/cycle to properly convert frequency from cycles/second to radians/second, but 2πf is such a tightly bound expression that even hardcore units nazis like myself are willing to treat it like a single variable and let it carry its units embedded -- but as soon as I replace the f with a numerical frequency (or some other expression), the r/cyc units get attached explicitly.

You answer for T is just a number, but time has units. If the units on that number are seconds, you need to specify that. Otherwise it's like saying that the depth of the water is 5. Five what? Five meters? Five inches? Five miles?

If it's seconds, a better way to express it would be

T = 269 ns
or
T = 0.269 µs
 

Thread Starter

leejohnson222

Joined Jan 11, 2023
57
sorry as ive not done this for over 14 years i am way worse than rusty
i got 2.689x 10^-7
to be fair you are helping me learn more than anyone else, its a shame your not my tutor
 

MrChips

Joined Oct 2, 2009
30,720
sorry as ive not done this for over 14 years i am way worse than rusty
i got 2.689x 10^-7
to be fair you are helping me learn more than anyone else, its a shame your not my tutor
Just to refresh your knowledge base:

T = 10^12
G = 10^9
M = 10^6
k = 10^3

m = 10^-3
μ = 10^-6
n = 10^-9
p = 10^-12

You have 2.689 x 10^-7 s
I will give you two ways to look at this.

Using 1 μs = 10^-6 s
1 s = 1 000 000 μs

2.689 x 10^-7 s = 2.689 x 10^-7 / 10^-6 μs = 2.689 x 10^-1 μs = 0.2689 μs

Another way to see this is:
2.689 x 10^-7 s = 2.689 / 10^7 = 2.689 / (10^7 x 10^-6) us= (2.689 / 10^1) μs = (2.689 / 10) μs = 0.2689 μs

Using 1 ns = 10^-9 s
1 s = 1 000 000 000 ns

2.689 x 10^-7 s = 2.689 x 10^-7 / 10^-9 ns = 2.689 x 10^2 ns = 268.9 ns

Also,
2.689 x 10^-7 s = 2.689 x (10^-7 x 10^9) ns = 2.689 x 10^2 ns = 2.689 x 100 ns= 268.9 ns
 

Thread Starter

leejohnson222

Joined Jan 11, 2023
57
amazing thanks, i will book mark that, i used to have an a4 sheet when i was doing my electrical qualifications for all these
and formula
 
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