# Search results

1. ### Thermodynamics, two equal volumes of gas at STP mix, entropy change?

Homework Statement Calculate entropy change if two equal volumes of gas (1 cm3) at standard temperature and pressure are separated from each other by a partition which is removed to create twice the volume at standard temperature and pressure Homework Equations dS = k.N. dV/V + C/T dT...
2. ### Characterize a co2 TEA class 4 laser

Homework Statement Im working on a lab experiment in my undergraduate physics degree requiring the use of a class 4 laser, i need to characterize this in terms of its power, coherence, pulse duration, wavelength and irradiance. This is a pulsed laser with rough parameters of 1-2J pulse energy...
3. ### Easy Question, Sunspots Astronomy Umbra and Penumbral sunspot areas

Didnt know if this is the write palce to put this, but im stuck on this assingment and i think it must have an easy solution so if someone could point me in the right direction then it would be much appreciated. Homework Statement Using an appropriate software package, quantify the...
4. ### Calculating values of electric and amgnetic fields of laser beam

Homework Statement A continuous wave laser beam in free space carries a power of 15w and has a circular cross section with diameter 1mm. Calculate peak values of the oscillatory electric and magnetic fields Eo and Ho repectively. Homework Equations Eox = (\mu/\epsilon)^1/2 Hoy \pir^2...
5. ### Calculate capacitance to adjust current in ac circuit

Homework Statement A Purely resistive resistive 100w, 110v lamp is to be supplied by an a.c. source of 230v r.m.s at 50Hz. what value of pure capacitance could be put in series to adjust the current flow to a suitable value? Homework Equations p=iv q=cv v=ir i know a number of other...
6. ### Reversible adiabatic expansion of ideal gas, entropy change?

Homework Statement One mole of an ideal gas at 0 celcius is subjected to changes below, calculate the change in entropy of the gas: i) Gas is expanded reversibly and isothermally to twice its initial volume. DONE - 5.76 J/K ii)A similar expansion to i. is performed reversibly and...
7. ### Thermodynamics Entropy change of the universe

Im trying to do an assingment for second year BSc, ive thrown alot of effort into quatum this semester so have fallen a little behind with thermodynamics so help is appreciated! Homework Statement Calculate the change in entrupy of the universe for the following processes A can of beer...