Question on Circuit1:Why the 20 ohm resistor is shorted when the switch is closed? Find the current through 10 ohm resistance when switch is closed.\nQuestion on Circuit2:In the steady state, why there is no current through branch cd?\n\nHere are the circuits\n\nCircuit 1: http://img206.imageshack.us/img206/2222/circuit12oz.jpg\nCircuit2: http://img131.imageshack.us/img131/1552/circuit27xi.jpg
137379
the 20 ohm is shorted because the current can go through the switch without going through the reisistor. when it is closed, R =10+1 =11, V =3, Current = V/R = 3/11 amps\n\nbecause direct current cannot cross a capacitor, which is in cd. this is because a capacicotr is plates which are parallel and do not touch. obviously, if the plates do not touch, electricity cannot flow through them. alternating current can go through a capacitor, only because the capacitor keeps discharging
544604
If the resistors are in parallel, then the voltage is the same across all of them - that's pretty much the definition of parallel.  If they are the only circuit elements, then that voltage will be the voltage of the circuit.  Since you didn't tell us what that voltage is, there's no way for us to figure the rest of the problem.  If you know the voltage, though, then Ohm's Law will give you the currents.
484067
An ideal voltmeter has infinite resistance: It is an open circuit. Although it is impossible to make a physical voltmeter with infinite resistance, a well designed voltmeter exhibits a very large internal input resistance. In some experiments, it is important to take into account the finite, non-ideal, internal resistance. To determine the internal resistance of the voltmeter, set up the circuit shown in figure . The voltmeter reads the voltage across itself, which includes its internal resistance. Since the circuit has only a single branch, the current flowing through the resistor also flows through the voltmeter.\n\nFor the required formulas and schematics, check out the reference.
427652
The resistance of the filament will increase as it heats up. So you're going to get something called a "transient", which is when the initial value will stabilize (to the working current in this case), after a period of time.\nA lower starting resistance equals a higher starting current.
190677
Number of turns doubled ; other things remain the same.\n\nTherefore, the voltage is doubled. Answer = 10 V.\n\nSelf inductance in the first case is  5 x 0.01 / 10 = 0.005 henry.\n\nSelf inductance in the second case is doubled = 0.01henry.
267740
Let's see if I can remember...\n\na) Find the current flowing through a DC circuit, from a 12V battery and a 3 ohm resistor.\n\nBy Ohm's Law, V = IR, where\n\nResistance = ohms = R\nCurrent = amperes = I\nVoltage = volts = V\n \nYou want to find the current, in amperes, so we switch the equation around a little: if V = IR, that also means that I = V/R (dividing both sides by the same thing gives the same answer).\n\nNow, plug in our values:\nI = (12 volts/ 3 ohms) = 4 amperes\n\nb) what is the current in an AC circuit, with 120 V and 60 W lightbulb.\nIn this case, Watts is a unit of power, and volts is a unit of resistance, and amperes is a unit of current. Electrical power is amperes times volts, or W = I * V\n\nIn this case, W = 60 and V = 120, so we rearrange it:\nW = I * V or \nI = W/V or \nI = (60 watts/120 volts) = 0.5 A\n\nAs for the atom model problem...hmmm! Si is the symbol for silicon. It has an atomic number of 14 (not 16) and an atomic mass of 28.085. According to the Bohr model of an atom, every atom has electrons (with no mass, and a negative charge), protons (with a mass, and a positive charge) and neutrons (with a mass, and no charge). The number of protons and electrons must be equal in order for the atom to have no charge, if one is greater than the other, it results in an ion (positive ion if protons are greater than electrons, negative ion if electrons are greater than protons). Electrons orbit around a nucleus of protons and neutrons.\n\nNow, an element's atomic number (14 in this case) is the same as the number of protons (and electrons, since the element is not an ion, in this case). So a silicon atom has 14 electrons orbiting around its nucleus, and its nucleus also has 14 protons and a number of neutrons.\n\nThe electrons orbit in shells around the nucleus. In the case of silicon, the inner shell has two electrons, the next shell has the maximum number possible or eight, and the third shell has the other electrons, or four. (To check, 2+8+4 = 14.) \n\nFinally, the number of neutrons in the nucleus can be calculated if we know how much a neutron weighs and how much a proton weighs. If N is the weight of a neutron, and P is the weight of a proton, and the number of neutrons is n1, and the number of protons is n2, and we say that the atomic weight is A, we have:\n\nA = (n1 * N) + (n2 * P)\n\nWe want to find n1, so we rearrange this like:\n(n1 * N) + (n2 * P) = A\n(n1 * N) = A - (n2 * P)\nn1 = (A - (n2 * P))/N\n\nNow all we have to do is plug in the relevant values, and we shall get the number of neutrons in an atom of silicon:\nA = 28.085\nn2 = 14\nP = \nN = \n\nSo, n1 = (A - (n2 * P))/N = \n\nSimple! Or at least, simpler! :)\n\nI know what you're going through...getting back into the swing of things after you've been away from school for a long time can be a pain. But keep on plugging away, it's worth it in the end! Good luck!
2250
I may be living in the past but I see transistors every day.  The 2-diode analogy is pretty close to the mark.  They meet at the base, pointing in for PNP and out for NPN.  Check them that way with your multimeter set on diode setting.  If the reading is inconclusive you may have to de-solder them from the circuit.
302167
First there is a correction to your statement.\n\nResistance increases with the length of the wire or conductor; but it decreases with the area of cross section of the wire or conductor. \n\nIt will give a wrong meaning if you use the word breadth instead of area of cross section.\n\nConsider a wire of length L and area of cross section A connected in a circuit. Let n be number of charges flowing through it under a given condition.\n\nNow connect a similar wire side be side with the previous one. (This is called parallel connection)\n\nAs before in the first wire there will be n number of charges flowing through it.\n\nWhat about the second wire. Since the condition is the same as the first one, in the second wire also there will be n number of charges flowing through it. \n\nThus if the area of cross section is doubled current is increased or resistance is decreased.\n\nIn a high way there is a bridge which is very narrow; the flow of vehicles will be less.\nIf the bridge is broadened the flow will increase.\n\nHowever the above is an analogy to make the concept some what to understand. But the charge in a wire is different from the vehicle flow.  \n\n\n\n.
521494
If you consider 2 nodes in a circuit, node A and node B, and you consider that node A has a higher potential than node B, then the current between A and B is 0.30 A, but the current between Node B and Node A is -0.30 A. See Kirchoff's laws.
481709
1. C\n2. C\n3. A  \n4. B\n\nnote: The resistances are measured in ohms, not kW.
25789
You'll have to describe the circuit a little better \n\nAre you adding either the 3.00 ohm or 2.50 ohm (but not both) in parallel with the 4.00 and 3.75 ohm, and need to know the total resistance with either the 3.00 or 2.50 ohm resistor connected?\n\nOr are BOTH the 3.00 AND the 2.5 ohm being placed in parallel with the 4.00 and 3.75 ohm?\n\nAnd without knowing the applied voltage, your first question (current through a 3.00, 4.00, 3.75, 2.50 ohm resistor) can't be answered.
517194
The resistance is increasing at .1785 ohms!!!\n\nJust use the ohm's law\n\n10/56=.1785 that's the resistance\n\nthen multiply the resistance and the current=volts\n\n.1785 x 56 =9.99999volts\n\nThis is the result.\n\nHope this help!!!
190433
Your question is confusing, but here I go.\n\nTo have zero current the circuit must be open.\nThat will give you the higher voltage.\nNow if you have a capacitor circuit, when you close the circuit will take some time to be zero current, while the capacitor charges.\nIn a inductor circuit the current is not possible to be zero because of the nature of the circuit, but will be near zero .\n\nIn a resistor circuit, the current never will be zero, the energy will become heat.\n\nso what are you trying to answer ???
330373
simple use two resistors, 6 and 3k ohm , in series and take the volatage across the 3 ohm resistor, it will be 3V.....\n\nuse the laws,\n\nif you have a voltage source, and two resistors p and q in series with it, \n\nthe voltage across p is given by  Vx(p/(p+q)), here u know voltage across p(Vp)= 3V, or 4.7 V or whatever....\n\nso, Vp = V x p/(p+q)....\n\nu know the value Vp, and V so substitute them......\n\n3 = 9 x p/(p+q)\n\nso p + q = 3p, \n\nso "2p = q", take two resistors ( in kilo ohms, coz u cant use just ohms, coz they are very large) such that one is double the value of other.......\n\nand connect the circuit across the 'p' resistor......\n\nwith 4.7, u get,\n\n4.7 = 9 x p/(p+q).....solve ...and choose resistors accordingly
591582
Remember the equation v/i=r, Keep the voltage constant over all the areas. If the resistance goes up, then the current goes down.\nIf you have zero ohms, you have a short. IF you have infinite resistance, you have a break.  This seems general, but this is a great help for most of the electronics applications you will need. \nIf you want more you will need to give us more info.
602003
You're confusing resistance with pressure. If indeed there is a difference in voltage between A and B then there will be flow.\nThink of a tank filled with water held a few feet above another tank that has a pipe joining the two. Water will flow to the lower container thru the pipe. In this case the pipe has no resistance, which means water flows at maximum possible speed.\nIf both tanks are at the same level, then, sure, there will be no water flow. That's not how the problem was stated, however.
317350
b) and c)\n\nthe transformer works in such a way that electric current flows through the secondary circuit only when the electric current in the primary circuit is changing.\n\nwhen you close the switch the electric current in the primary circuit suddenly rises from 0amp to some value\nwhich causes electric curent to flow through the secondary circuit\n\n.. b) is true\n\nwhen you open the switch the electric curent in the primary circuit changes from the maximum value to 0amps thus electric curent flows through the secondary.\n\n.. c) is true\n\nbut \n..a) is false\n\nsicne a battery is a dc source wich means that as long as the switch is closed it supplies a steady amount of electric current through the primary. thus ther will be no current through the secondary.