Accurate Measurements on pulsed system's harder than you think.

[tinman]

.... even changing (+) and (-) tips of your multimeter may completely change the scene. (-) is connected with the shield and has higher capacitive load to ground as the (+) tip.

In the first video,the pulse motor will be running from a battery,and we will be using the scope to measure the voltage across a CVR,and the voltage across the incandescent bulb.
If the avreage voltage across the CVR rises,then that tells us the average current has risen. If you raise the avarage current flowing through an incandescent bulb,then you also raise the avaerage voltage across that incandescent bulb-which means you should be now dissipating more power from that bulb-->in the way of heat and light. The more power you disipate from an incandescent bulb,the brighter it shine's-the more light it puts out.


Brad.

[gyulasun]

Hi Gyula

Both voltage and current will rise together with an incandescent bulb. This makes them linear.
...

Just uploaded the current-voltage characteristic of an incandescent lamp in my previous post.  You are right that both voltage and current will rise but NOT linearly with each other like with a normal resistor.
LEDs are also nonlinear loads, and I agree with what you wrote on them.

EDIT  Yes, when we know the average current via a light bulb and we know the average voltage across it, we can use Ohm's law in that case.   

Gyula

[tinman]

Just uploaded the current-voltage characteristic of an incandescent lamp in my previous post.  You are right that both voltage and current will rise but NOT linearly with each other like with a normal resistor.
LEDs are also nonlinear loads, and I agree with what you wrote on them.

Gyula

Gyula

That is a lumens output curve per V/A,not a voltage/current curve.

Anyway,regardless of that,we know ohms law still applies,in that we can safely say that the dissipated power from the bulb should increase if the current flowing through it increases,and the voltage across it increases. This should result in more light output-should it not?,as this is how incandescent bulbs work.

Brad

[tinman]

OK,here is the first video,and i am off to make the second.

https://www.youtube.com/watch?v=QfqvIjABXZ8

[gyulasun]

Dear Brad,

In the meantime I added a sentence to my previous post and the use of Ohm's law is ok for the average current and voltage for an incandescent bulb. 

The VI curve I took from the video link was done from the current and voltage measurements, they changed the voltage across the lamp from zero to about 6 V and measured the current with an Ammeter in series with the lamp.  Of course the brightness of the lamp changes as the voltage across the lamp changes.

Gyula