Analyzing Franck Hertz Graph on Excel/Matlab

[jenny777]

Hello,

How can I determine when the current is starting rise? What methods should I use to do so? on excel or matlab.

I've attached an image of my graph below

Thanks a million

 

[Jilang]

Er, can you use a ruler?

 

[jenny777]

that's what I did on my last lab, for Planck's constant, but apparently I need some systematic way of determining it according to my TA

 

[jenny777]

I'm writing a formal lab report for Franck Hertz oscillation

 

[Jilang]

Can you plot the gradient using Excel. Then if possible say when the increase in the gradient becomes statistically significant?

 

[jenny777]

how do I find the gradient? (sorry I'm not really good at this)

 

[Jilang]

Or may get Excel to determine the best fit line. It will tell you the equation of the line and where is crosses the x axis.

 

[Jilang]

If you don't know how look up trend lines in Excel help.

 

[jenny777]

I tried fitting an exponential and linear line, but it didn't work. it was way too off. But why would the would I be looking for a y-intercept of the line? (where it crosses the origin)

 

[jenny777]

oops, i meant to say why would I be, not why would the would I ...haha

 

[Jilang]

how do I find the gradient? (sorry I'm not really good at this)

Rather than plot the current, you could plot the change in the current. That would be the change in each current measurement divided by the each little change in your input variable. That would be the gradient.

 

[Jilang]

I tried fitting an exponential and linear line, but it didn't work. it was way too off. But why would the would I be looking for a y-intercept of the line? (where it crosses the origin)

Sorry, I meant the x axis. And you can't use all the points - you need to exclude the flat part, else you will get rubbish.

 

[jenny777]

I think the gradient plot sounds good! thanks so much!