jinny1's Physics Questions Thread

[jinny1]

Thanks in advance

[Vincezor]

A diagram would be nice...

[jinny1]

Why is the bottom of "I" beams in tension?? Arent they in compression if they are stacked on top of each other??

[jinny1]

anyone ?

[Bozo]

Wheres this question from?

[jinny1]

Ive been reading that in various sources. For eg physics notes A+ book in pg 76. "I or T girders are designed so that the maximum cross-sectional area is present where the beam is likely ro be acting under compression or tension (top and bottom, respectively)" arent the beams those long things that are stacked on top of each other??? If so osnt the bottom in compression?

[jinny1]

i was also wonder ing what they meant by peak-to-peak voltage.

LEts say an input volatage has 20mV peak-to-peak, does this mean the maximum input voltage is 20mV or the difference of voltage between to highest/lowest input voltage is 20mV?

[Vincezor]

i was also wonder ing what they meant by peak-to-peak voltage.

LEts say an input volatage has 20mV peak-to-peak, does this mean the maximum input voltage is 20mV or the difference of voltage between to highest/lowest input voltage is 20mV?

The Peak-to-peak voltage is the difference between the peak and the trough (Highest amplitude to lowest amplitude). Also take care that since it says PEAK, you are not measuring in RMS voltage.

[jinny1]

Thanks mate. What do you mean by RMS voltage?? What wud the difference be between a peak2peak 20v and a RMS 20v

[cohen]

The RMS voltage equivalent of a Peak-To-Peak 20v would be

, which is roughly 7.07

I believe the RMS voltage is the Direct current voltage. (If you have the heinemann book, they talk about RMS voltage in the further electronics section.

Edit: Just googled it.

the root-mean-squae (RMS) value of an alternating voltage is the equivalent d.c. voltage

[jinny1]

thanks heaps

[Vincezor]

thanks heaps

Sorry to bother, but is there anything on RMS Voltage in the core studies? (Electronics and Photonics) Because I'm doing the further electronics detailed study so I'm not entirely sure if I've seen a question relating to it on trial exam papers.

[jinny1]

thanks heaps

Sorry to bother, but is there anything on RMS Voltage in the core studies? (Electronics and Photonics) Because I'm doing the further electronics detailed study so I'm not entirely sure if I've seen a question relating to it on trial exam papers.

Well sometimes trial exams say that this circuit has a RMS of "x" mV. But you do not need to know what that means or explain it, as far as i know.

[jinny1]

just a question here

Would you still call a material ductile if it stretches a lot in the elastic region, but ultimately brittle as it has little plastic characteristics??? or does it have to stretch a lot in the plastic region only, to be called ductile//

[EvangelionZeta]

It's basically just the plastic region. However, if you're asked to judge which of two materials (which are both brittle) is the most ductile, then you'd probably say the one which stretches more in the elastic region (although it's not strictly ductile).