Recent content by alexburns1991

Homework Statement An opaque bag contains 10 green counters, and 20 red ones. One counter is drawn at random and not replaced: green scores one, red scores zero. Five counters are drawn. Find the probability of scoring 0, 1, 2, 3, 4, 5 points. Homework Equations The Attempt at...

well i get \frac{2du}{\sqrt{a}+\frac{\sqrt{b}}{x}} = dx leading to and then -(\sqrt{ab}+2u^{2}) = -\frac{1}{2}(ax^{2}+\frac{b}{x^{2}}) x=\frac{u}{\sqrt{a}}\pm \sqrt{\frac{u^{2}}{a}+\sqrt{\frac{b}{a}}} which i make completely unhelpful all in all, this gives me an integral...

Homework Statement \int e^{-\frac{1}{2}(ax^{2}+\frac{b}{x^{2}})} dx from -\infty to \infty Homework Equations it says to solve this, given that, again from -\inftyto \infty: \int e^{-\frac{1}{2}x^{2}}}dx = \sqrt{}2\pi and suggests that the substitution u =...

sorry i copied the question wrong, it was meant to be 100kilo ohms. i still don't see how you can get the answer given though.

Homework Statement A 50 \muF capacitor is being charged from a 6V battery via a 100k\Omega resistor . what is the initial charging current? after a period of time, the charging current is 30\muA. what are the pd's across the resistor and the capacitor at that moment? how much charge has been...

i worked it out to be 0.2A. ive just posted another question on this, where my answer disagrees with the answer in the book. i think the solution should be to get a new book!

Homework Statement Using kirchhoff's laws, calculate the current in the 2 ohm resistor. Picture of the circuit attached. Homework Equations kirchhoff's laws, and ohms law The Attempt at a Solution i3 = i1 - i2 then i used kirchhoff's law to get: 2 - i1 = 2.i2 and 1 - 2 (...

you can get the answers in the book by taking the currents in the parallel equation as being the same, both 0.1875- which gives r = 1, but i don't see why this would be the case at all. surely taking one complete loop and applying kirchhoff's rule, the current through each of the cells would be...

im a bit suspicious of the answers in the book, theyve been wrong before! but i don't want to assume that its always the book that's wrong, so maybe I've missed something? the equations i got give E = 4.5V and r = 10 ohms, which i think seems too high.

Homework Statement two identical cells of emf E and internal resistance r are connected in series. a 7 ohm resistor is connected across the combination and draws a current of 0.333A. the two cells are now connected in parallel; the 7 ohm resistor now draws a current of 0.375A from the...