Bay 12 Games Forum

Please login or register.

Login with username, password and session length
Advanced search  

Author Topic: Yet another physics help thread  (Read 584 times)

Kicior

  • Bay Watcher
    • View Profile
Yet another physics help thread
« on: March 31, 2014, 01:07:54 pm »

I'm pretty sure there was an official physics help thread but I can't find it.

I've got 2 questions:
1)How do I count voltage drops on resistors, capacitors and coils in a RLC circuit? Use impedance to find out the current and then multiply it by resistance, capacitance and inductance? Is it not weird that the total voltage drop is higher than the voltage? :P

R=1000 O
L=2H
C=20*10-6 F
U=230V f=50Hz

Z=sqrt(R^2+(Rl-Rc)^2)=sqrt(10*10^6+(628-1592)^2)=sqrt(10^6+(-964)^2)=sqrt(1929296)=1389 O
I=U/R=230/1389=0.17 A (or should I use effective voltage?)

Voltage drop on the resistor  170 V (119V when using RMS)
on the coil 106.76V (74.7V)
on the capacitor 270.64 (189.44V)

2) There is a tuning fork on a resonance box, the resonance box is a rectangular box with one of the walls missing. The tuning fork is making a sound, will the frequency change when you cover the missing wall? The answer is no but why? Shouldn't the length of the standing wave change because at first there was an equal amount of nodes and anti-nodes but then there is one more node after the hole is covered?  (let's say it looks something like this |===   the wave "starts" with a node and "ends" with an anti-node, later it's like this |===| the wave "starts" with an anti-node and "ends" with an anti-node)


Logged
and slippedy sloppidy doo everything is made of fuck

zombie urist

  • Bay Watcher
  • [NOT_LIVING]
    • View Profile
Re: Yet another physics help thread
« Reply #1 on: March 31, 2014, 09:56:32 pm »

For question 1 just use V = IZ. I don't know what you mean by effective voltage. The total voltage around a loop should be zero. I also don't think you need RMS. Remember that impedance depends on frequency for capacitors and inductors. Your equivalent impedance also depends on the layout of the circuit.

No idea on 2.
Logged
The worst part of all of this is that Shakerag won.

Skyrunner

  • Bay Watcher
  • ?!?!
    • View Profile
    • Portfolio
Re: Yet another physics help thread
« Reply #2 on: April 07, 2014, 04:09:24 am »

I thought tuning forks have little to do with standing waves and just emits sound o.o
Logged

bay12 lower boards IRC:irc.darkmyst.org @ #bay12lb
"Oh, they never lie. They dissemble, evade, prevaricate, confoud, confuse, distract, obscure, subtly misrepresent and willfully misunderstand with what often appears to be a positively gleeful relish ... but they never lie" -- Look To Windward