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[Kicior]

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?

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)

[zombie urist]

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.

[Skyrunner]

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