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• Users: logearav
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1. ### Solving an equation involving Coulomb's law

Thanks Mr. Charles Link. In the first solution i get the q12 -6*10-6q1 -16*10-12 = 0 and for second one i get q12 - 6*10-6q1-16*106 = 0. My question is why i get different powers for the term involving -16.
2. ### Solving an equation involving Coulomb's law

Homework Statement Hi Members, I have solved an equation involving Coulomb's law in two ways and have posted the images of the same. I get two types of equations. Please help me to find where i gone wrong? Homework Equations The Attempt at a Solution
3. ### Quantisation of Charge

Homework Statement Quantisation means charge always exist in integral multiples of magnitude of charge of electron and to put it mathematically we say q = ne, where n is an integer 1,2,3,4 ... -1,-2,-3,... etc. Numerous print and web materials say that charge cannot exist in fraction or...
4. ### Finding the magnitude and direction of current thro Kirchhoff law

Thank you gneill and rude man for your help.
5. ### Finding the magnitude and direction of current thro Kirchhoff law

Homework Statement Revered Members, Please go through my attachment. I have been asked to find the magnitude and direction of current through the 10 ohm resistor. The answer that is given in the book is 1/23 Ampere from A to B. But i solved as given in the attachment but i got the answer...
6. ### Factors on which conductivity depends

Homework Statement The conductivity of a material depends on a) Resistance(R) b) Area of cross section(A) c) Length(L) d) Resistivity(ρ) Homework Equations The Attempt at a Solution The formula for Resistivity is given by ρ = AR/L and Conductivity(σ) being the reciprocal of...
7. ### Frictional charging and weight of the body involved

Homework Statement If a body is charged by rubbing it, its weight a) may slightly increase of slightly decrease b) increases slightly c) decreases slightly d) remains constant Homework Equations The Attempt at a Solution I know weight is nothing but gravitational force...

Thanks TSnY.
9. ### Induced Current and Eddy Current

Homework Statement I want to know whether Eddy current and Induced Current are same? Homework Equations The Attempt at a Solution 1)When flux linked with a circuit changes, an emf is induced in the circuit and this emf is called induced emf and the current is called induced...
10. ### Position and acceleration vector - parallel and perpendicular

Thanks gneill. But this is how the question appears in University Exam paper.
11. ### Position and acceleration vector - parallel and perpendicular

Position and acceleration vector -- parallel and perpendicular Homework Statement The motion of a particle is defined by the position vector r = A(Cos t + t Sin t) i + A(Sin t + t Cos t) j where t is expressed in seconds. Determine the values of t for which the position vector and...
12. ### Tension in the string rope

Thanks a lot Spinnor. So nice of you in explaining the things so beautifully.
13. ### Capacitors in series homework

Capacitors are connected in series. So the effective capacitance is 1/Cs = 1/C + 1/2C + 1/3C = 11/6C Cs = 6C/11 Now substitute this value for C for the equation V = 11/6(Q/C) you ll get Q/C which is nothing but V or V1 Hope you got it now
14. ### Capacitors in series homework

I can't get you. Actually is 11/6 times the V
15. ### Capacitors in series homework

V = q/c so v = q/c + q/2c + q/3c q/c(1+1/2+1/3) q/c (11/6) hope this helps
16. ### Tension in the string rope

Homework Statement 1) A box of mass 42kg sits on the top of a ladder. Neglecting the weight of the ladder, find the tension in the rope. Assume the rope exerts horizontal forces on the ladder at each end. Homework Equations m1g – T = m1a The Attempt at a Solution T = m1g - m1a...
17. ### Resistance and Temperature in conductors and semiconductors

Homework Statement Revered Members, When we increase the temperature, resistance increases in conductors. But resistance decreases in semiconductors. Why? Help in this regard will be highly appreciated. Homework Equations The Attempt at a Solution Due to increase in temperature...
18. ### Coulomb's law in vector form

Thanks again. If charges are opposite, then attractive force exists. Will the coulomb law take a negative sign? That is F = -KQ1Q2/r^2 ?

20. ### Coulomb's law in vector form

Sorry cupid.callin. Now i have incorporated the attachments.
21. ### Coulomb's law in vector form

Homework Statement Revered members, Please see my both attachments. Homework Equations F21 = (q1q2/4∏ε0r122)*r12cap(unit vector) Is it wrong to use r12 instead of r21 for F21. Because my second attachment uses r21 for F21 and r12 or F12. I am confused. Please help which is correct...
22. ### Effective Resistance if bent in the form a circle

Thanks a lot stonebridge. Your help is very much appreciated
23. ### Electric potential - doubt in sign convention

Thanks a lot ehild. The link you have given is so wonderful. I understood the concept. Thanks again.
24. ### Electric potential - doubt in sign convention

ok. Now i am confronted with the magnitude of test charge and source charge. Should they be of same magnitude? I presume the test charge is unit positive charge. But i can't get an idea of magnitude of source charge, in the concept of electric potential
25. ### Electric potential - doubt in sign convention

Thanks again. How could we find which point is more positive?
26. ### Electric potential - doubt in sign convention

Thanks ehild. Now, if i choose a point A say 5 cm from X and B at 9 cm from X, which is the point with higher potential?
27. ### Electric potential - doubt in sign convention

Thanks for the detailed explanation, ehild. What is the position of the two points A and B in a electric field? For example, i draw a straight line XY. Where should i position the points A and B that satisfies your explanation? X_________________________________________y
28. ### Electric potential - doubt in sign convention

Electric potential --- doubt in sign convention Homework Statement Revered members, I know dV = -E.dx so E = -dV/dx So E should be E = -V/x . But while deriving capacitance of a parallel plate capacitor when dielectric medium is introduced we use E = V/x. But how E = V/x? Homework...
29. ### Metacentric height

Thanks Spinnor, i meant tanθ, which i erroneously entered as cos. So θ = .02. Do the formula i used to arrive at the solution is correct?
30. ### Metacentric height

Homework Statement In a ship of 10000 tons, the breadth of whose deck is 20 m, a mass of 50 tons is moved from one side to the other causing the bob of a plumb line 10 m long to move over 20 cm. Find the metacentric height? Homework Equations The Attempt at a Solution I don't...
31. ### Change in entropy

Homework Statement What is the change in entropy when 1 gm of ice at 0° C is converted into water at the same temperature? Homework Equations [b]3. The attempt at the solution dS = dQ/T. Q = msT/T so dS = 1*?*273/273 i don't know whether i should substitute specific heat...
32. ### Effective Resistance if bent in the form a circle

Homework Statement A wire of resistance 8R is bent in the form of a circle. What is the effective resistance between the ends of a diameter AB? Homework Equations I have attached the image and my attempt to solve it as told by my teacher. Homework Equations The Attempt at...
33. ### Application of Gauss' law - some doubts

My fourth attachment.
34. ### Application of Gauss' law - some doubts

Application of Gauss' law -- some doubts Homework Statement Revered Members, I have attached images of applications of Gauss' law namely 1) Electric field due to an infinitely long charged wire and 2) Electric field due to an infinite charged plane sheet. In both cases Gaussian surface is...
35. ### Resolution of vectors

Thanks omoplata. I raised this query in many forums but i could not get any satisfactory reply. Now with your example, i clearly understood the concept. Persons like you are an asset to this forum. Thanks a lot for your valuable help.
36. ### Resolution of vectors

Omaplata, one more doubt. Why vsinθ has no effect in measurement of velocity? Only vcosθ has been taken into account. It has been mentioned since vsinθ is perpendicular to the vertical diameter, it has no effect. I don't understand. Could you clarify?
37. ### Resolution of vectors

Thanks for your kind gesture omaplata. I understood now.
38. ### Surface Tension and Potential Energy

Homework Statement When we consider a beaker of water and two molecules, one completely inside the water and the other at the free surface, the water molecule at the free surface will experience net downward force of attraction and this causes the water molecule to behave like a stretched...
39. ### Fermi Level - clarification needed

Thanks ehild. So, Fermi level is the level above valence band,am i right?
40. ### Fermi Level - clarification needed

Fermi Level -- clarification needed Homework Statement Revered Members, Can i know what is meant by fermi level? I googled this, but i could not understand. One site says Fermi level as top of collection of electron energy levels at absolute zero. Homework Equations The Attempt...
41. ### Paramagnetic and diamagnetic substances

Homework Statement Revered Members, Please see me my attachment. Homework Equations When paramagnetic substances are placed in non uniform magnetic field, they have a tendency to move from weaker to stronger part Similarly, when diamagnetic substances are placed in non uniform...
42. ### Capacitors - what does same potential mean?

Capacitors -- what does same potential mean? Homework Statement Revered members, When the capacitor is fully discharged, the plates of capacitor are at same potential. I want to know the interpretation of the term same potential. Homework Equations The Attempt at a Solution...
43. ### Emission or absorption spectrum

Homework Statement X rays give continuous spectrum and line spectrum. Whether these spectrums are emission or absorption spectrum? Homework Equations The Attempt at a Solution I think it is emission spectrum, because there is no absorbing material. Still, i need confirmation from...
44. ### Laser action and stimulated emission

Thank you Redbelly and Simon. So, when the electron releases photon when it comes to E2, we supply again a photon of energy E2 - E1 and the supplied photon acts as stimulating photon. Am I right?
45. ### Laser action and stimulated emission

Thanks for the reply Simon. So I infer that the electron in the metastable state has already has an absorbed photon, and if we supply a photon of energy E2 - E1 externally, then this photon plus the absorbed photon are emitted and both are in same phase. Am I right?
46. ### Laser action and stimulated emission

Homework Statement Revered Members, An electron in ground state makes its way to an excited state upon absorption of photon of energy, equivalent to energy difference between ground state and excited state, and after some time, it decays by emitting the photon and returns to the ground...
47. ### Difference between mass and volume

Homework Statement I have a beaker of capacity 500 ml and i fill it with 250 ml. Now, what is mass and volume of water? Homework Equations The Attempt at a Solution Volume is the space occupied by matter, so i presume 250 ml is the volume of water. Mass is the quantity of matter...
48. ### Free particle and some doubts

Thanks a lot HallsofIvy.
49. ### Free particle and some doubts

Homework Statement Revered members, A free particle is one which has no forces acting on it and since there is no forces acting on it, so there is no potential energy and E is entirely kinetic. Homework Equations The Attempt at a Solution My doubt is, when no forces act on a...
50. ### Electromagnetic waves and phase difference

@ehild, I got it now. Thanks a lot. @Vela Thanks for clarifying. I read your post again with inputs from ehild and i got it now. Thanks a lot, Vela, for your reply.