Experiment to show that current leads voltage by 90 degrees in capacitor (Using RC circuit and Oscilloscope)

Started by August 10, 2020
```Many books told me that current leads voltage by 90 degrees in capacitor.
So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.

Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
```
```yuenhonkeung@gmail.com wrote:
> Many books told me that current leads voltage by 90 degrees in capacitor.
> So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>
> Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A

Good video. I like the mention of the ground lead connection.

```
```On Monday, 17 August 2020 at 13:59:41 UTC+8, Cydrome Leader wrote:
> yuenho...@gmail.com wrote:
> > Many books told me that current leads voltage by 90 degrees in capacitor.
> > So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
> >
> > Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
> Good video. I like the mention of the ground lead connection.
Thanks!
```
```????????? Edward Yuen <yuenhonkeung@gmail.com> wrote:
> On Monday, 17 August 2020 at 13:59:41 UTC+8, Cydrome Leader wrote:
>> yuenho...@gmail.com wrote:
>> > Many books told me that current leads voltage by 90 degrees in capacitor.
>> > So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>> >
>> > Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>> Good video. I like the mention of the ground lead connection.
> Thanks!

I get a good laugh out of half melted ground leads on oscilloscopes.
```
```On Monday, August 17, 2020 at 3:59:41 PM UTC+10, Cydrome Leader wrote:
> yuenhonkeung@gmail.com wrote:
> > Many books told me that current leads voltage by 90 degrees in capacitor.
> > So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
> >
> > Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>
> Good video. I like the mention of the ground lead connection.

** If the presenter had simply used an analogue scope - he could have employed a Lissajous pattern to prove the fact is a few seconds.

In phase  =  diagonal line

45 degree shift ( -3db_) = ellipse.

90 degree  = circle.

.....   Phil
```
```On 2020-09-10, Phil Allison <pallison49@gmail.com> wrote:
> On Monday, August 17, 2020 at 3:59:41 PM UTC+10, Cydrome Leader wrote:
>> yuenhonkeung@gmail.com wrote:
>> > Many books told me that current leads voltage by 90 degrees in capacitor.
>> > So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>> >
>> > Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>>
>> Good video. I like the mention of the ground lead connection.
>
> ** If the presenter had simply used an analogue scope - he could have employed a Lissajous pattern to prove the fact is a few seconds.
>
> In phase  =  diagonal line
>
> 45 degree shift ( -3db_) = ellipse.
>
> 90 degree  = circle.
>

Ah! the memories - back in school in the 1960's, baffling the physics
teacher by hooking up the sig. gens to not only the front X input but
the Y input at the back - and another on the Z input to get travelling
spots.
```
```On 11.09.20 21:34, Jim Jackson wrote:
> On 2020-09-10, Phil Allison <pallison49@gmail.com> wrote:
>> On Monday, August 17, 2020 at 3:59:41 PM UTC+10, Cydrome Leader wrote:
>>> yuenhonkeung@gmail.com wrote:
>>>> Many books told me that current leads voltage by 90 degrees in capacitor.
>>>> So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>>>>
>>>> Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>>>
>>> Good video. I like the mention of the ground lead connection.
>>
>> ** If the presenter had simply used an analogue scope - he could have employed a Lissajous pattern to prove the fact is a few seconds.
>>
>> In phase  =  diagonal line
>>
>> 45 degree shift ( -3db_) = ellipse.
>>
>> 90 degree  = circle.
>>
>
> Ah! the memories - back in school in the 1960's, baffling the physics
> teacher by hooking up the sig. gens to not only the front X input but
> the Y input at the back - and another on the Z input to get travelling
> spots.
>
Aaah! Those old times....
I used x,y input, to put text on a scope screen,
with 2 dao's from an ordinary 80-286 computer.
Worked fine.
just visit each point which needed licht,
movement from one point to the next, was fast enough
to only show as dark lines,
```
```On 2020-09-11, Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
> On 11.09.20 21:34, Jim Jackson wrote:
>> On 2020-09-10, Phil Allison <pallison49@gmail.com> wrote:
>>> On Monday, August 17, 2020 at 3:59:41 PM UTC+10, Cydrome Leader wrote:
>>>> yuenhonkeung@gmail.com wrote:
>>>>> Many books told me that current leads voltage by 90 degrees in capacitor.
>>>>> So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>>>>>
>>>>> Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>>>>
>>>> Good video. I like the mention of the ground lead connection.
>>>
>>> ** If the presenter had simply used an analogue scope - he could have employed a Lissajous pattern to prove the fact is a few seconds.
>>>
>>> In phase  =  diagonal line
>>>
>>> 45 degree shift ( -3db_) = ellipse.
>>>
>>> 90 degree  = circle.
>>>
>>
>> Ah! the memories - back in school in the 1960's, baffling the physics
>> teacher by hooking up the sig. gens to not only the front X input but
>> the Y input at the back - and another on the Z input to get travelling
>> spots.
>>
> Aaah! Those old times....
> I used x,y input, to put text on a scope screen,
> with 2 dao's from an ordinary 80-286 computer.
> Worked fine.

Lovely - but in the late 1960's the school I was at didn't have a
computer :-)

But back in the 40's scopes, well CRTs, were used as RAM for some of the
first progammable computers.

https://en.wikipedia.org/wiki/Williams_tube

> just visit each point which needed licht,
> movement from one point to the next, was fast enough
> to only show as dark lines,
```
```Jim Jackson <jj@franjam.org.uk> wrote:
> On 2020-09-11, Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
>> On 11.09.20 21:34, Jim Jackson wrote:
>>> On 2020-09-10, Phil Allison <pallison49@gmail.com> wrote:
>>>> On Monday, August 17, 2020 at 3:59:41 PM UTC+10, Cydrome Leader wrote:
>>>>> yuenhonkeung@gmail.com wrote:
>>>>>> Many books told me that current leads voltage by 90 degrees in capacitor.
>>>>>> So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>>>>>>
>>>>>> Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>>>>>
>>>>> Good video. I like the mention of the ground lead connection.
>>>>
>>>> ** If the presenter had simply used an analogue scope - he could have employed a Lissajous pattern to prove the fact is a few seconds.
>>>>
>>>> In phase  =  diagonal line
>>>>
>>>> 45 degree shift ( -3db_) = ellipse.
>>>>
>>>> 90 degree  = circle.
>>>>
>>>
>>> Ah! the memories - back in school in the 1960's, baffling the physics
>>> teacher by hooking up the sig. gens to not only the front X input but
>>> the Y input at the back - and another on the Z input to get travelling
>>> spots.
>>>
>> Aaah! Those old times....
>> I used x,y input, to put text on a scope screen,
>> with 2 dao's from an ordinary 80-286 computer.
>> Worked fine.
>
> Lovely - but in the late 1960's the school I was at didn't have a
> computer :-)
>
> But back in the 40's scopes, well CRTs, were used as RAM for some of the
> first progammable computers.
>
>  https://en.wikipedia.org/wiki/Williams_tube
>
>> just visit each point which needed licht,
>> movement from one point to the next, was fast enough
>> to only show as dark lines,

When did they stop making those memory CRT tubes for scopes and raster
display for old computers?
```
```Cydrome Leader <presence@mungepanix.com> wrote:
> Jim Jackson <jj@franjam.org.uk> wrote:
>> On 2020-09-11, Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
>>> On 11.09.20 21:34, Jim Jackson wrote:
>>>> On 2020-09-10, Phil Allison <pallison49@gmail.com> wrote:
>>>>> On Monday, August 17, 2020 at 3:59:41 PM UTC+10, Cydrome Leader wrote:
>>>>>> yuenhonkeung@gmail.com wrote:
>>>>>>> Many books told me that current leads voltage by 90 degrees in capacitor.
>>>>>>> So, I designed an experiment to show that it is true. You can do the experiment at home or in the laboratory.
>>>>>>>
>>>>>>> Here is my experiment in youtube: https://www.youtube.com/watch?v=wjQsyLv0X7A
>>>>>>
>>>>>> Good video. I like the mention of the ground lead connection.
>>>>>
>>>>> ** If the presenter had simply used an analogue scope - he could have employed a Lissajous pattern to prove the fact is a few seconds.
>>>>>
>>>>> In phase  =  diagonal line
>>>>>
>>>>> 45 degree shift ( -3db_) = ellipse.
>>>>>
>>>>> 90 degree  = circle.
>>>>>
>>>>
>>>> Ah! the memories - back in school in the 1960's, baffling the physics
>>>> teacher by hooking up the sig. gens to not only the front X input but
>>>> the Y input at the back - and another on the Z input to get travelling
>>>> spots.
>>>>
>>> Aaah! Those old times....
>>> I used x,y input, to put text on a scope screen,
>>> with 2 dao's from an ordinary 80-286 computer.
>>> Worked fine.
>>
>> Lovely - but in the late 1960's the school I was at didn't have a
>> computer :-)
>>
>> But back in the 40's scopes, well CRTs, were used as RAM for some of the
>> first progammable computers.
>>
>>  https://en.wikipedia.org/wiki/Williams_tube
>>
>>> just visit each point which needed licht,
>>> movement from one point to the next, was fast enough
>>> to only show as dark lines,
>
> When did they stop making those memory CRT tubes for scopes and raster
> display for old computers?

correction, vector displays.
```