Recent content by haleycomet2

thanks for your opinions,=)

Which is better,NUS or NTHU?[urgent] I am going to study physics degree and i plan to study phD or master in astrophysics in phD or master in future.However,i am struggling choosing National Tsinghua University(taiwan) or (NUS)National University of Singapore.I think i may learn more in...

What a brilliant software!I can use this to check my work in future.Thank you!:smile:

o,i see.Thanks a lot:smile:

\frac{Ax^2 +1}{x^3(x-1)^2}=\frac{B}{x}+\frac{C}{x^2}+\frac{D}{x^3}+\frac{E}{x-1}+\frac{F}{(x-1)^2} It is clear that constant B and E have to be zero so that P(x) is rational.However.the value of A is different when solving the equation,after eliminating other variable and only one variable(B...

Homework Statement \int\frac{dx}{x-\sqrt{1-x^2}} Homework Equations The Attempt at a Solution i try to simplify it by multiplying \frac{x+\sqrt{1-x^2}}{x+\sqrt{1-x^2}},becoming =\frac{x+\sqrt{1-x^2}}{2x^2-1} =\int{\frac{x}{2x^2-1}+\frac{\sqrt{1-x^2}}{2x^2-1}}dx ps: a.Can i...

Homework Statement Find the second degree polynomial P(x) such that P(0)=1,P'(0)=0,and \intP(x)/{x3(x-1)2} dx is a rational function Homework Equations this chapter is about integration techniques,L'Hopital's Rule, and Improper Integral partial fraction,partial integration are...

If wavelength depend only on cavity size,then the frequency of sound is higher as the speed of gas becomes higher(cavity size stay constant when we make comparison of two gases ). However, some says that the frequency is only depend on vocal folds and it is independent of the gas.And the only...

Our sound will be like "Donald Duck" if we inhale helium gas and the explanation from web is because" The cavity resonances which determine the vocal formats would be raised by the higher sound speed,"(http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html). Why cavity resonance raise as...

Could anyone suggest any link or books which have a deeper introduction of inductor(i have read“all about circuit” ,"hyperphysics" website,and A-level physics by Nelkon and Parker)?I am sorry for troubling u all and maybe i need time to study more and think more to understand this. Thank you.

Ya,this is what i think.However,i notice that the in the book ,it is written that "To maintain the current,the applied supply voltage must be equal to the back emf.The voltage applied to the coil must therefore be given by V=L dI/dt." when deduce the voltage of pure inductor circuit. So I am...

I think that back emf is not in phase with current,but is the differentiation of current.This is why i feel that it may not equal to the terminal voltage across inductor. Besides,since current always flow in direction with the NET voltage.From the graph,sometimes the sign of supply voltage(or...

I think that back emf is not in phase with current,but is the differentiation of current.This is why i feel that it may not equal to the terminal voltage across inductor. Besides,since current always flow in direction with the NET voltage.from the graph,sometimes the sign of supply voltage(or...

Referring to the graphs below(with or without resistance),the sign of current sometimes is in opposite with the voltage.Does this happened when back emf is greater than supply voltage or how to explain this? ps:these pictures are originally from http://www.allaboutcircuits.com/vol_2/chpt_3/2.html

What i can't understand is if I=V/jX =1/jX(sin t),then back emf will be Ldi/dt=L/jX(cos t),which is 90 degree out of phase of supply voltage.Doesn't back emf is always nearly equal (or at least in phase) to the supply voltage?? ps: jX =reactance right?? Thanks a lot.