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  1. n.karthick

    Switching from parallel to series and keeping restistance the same.

    Oh I didn't notice that it is the current through X which is same, sorry. Equating voltage across X in both cases and solving that should give Y.
  2. n.karthick

    Switching from parallel to series and keeping restistance the same.

    I can give u a hint. Because the current is same (i) when Y is connected and (ii) Y disconnected and 50 ohm connected in circuit it means that total resistance in the circuit is same for both the cases. So you can equal the total resistance in 2 cases and solve for Y.
  3. n.karthick

    Ohm's Law

    Take it this way, you can apply any amount of voltage to a conductor, measure the current flowing through the conductor, now find ratio of voltages and corresponding current values. You will find that for different values of voltages applied and the corresponding V/I ratios are always the same...
  4. n.karthick

    Ohm's Law

    For (1), Ohm's law is the answer which states that I \propto V in a conductor while temperature remains constant. The constant of proportionality is the inverse of resistance (R) of that conductor. Ohm has done many experiements and discovered that the above relation holds in conductors and now...
  5. n.karthick

    RC circuit problems

    If you want to find I0, you should know V0. But what is V0? Do you know the capacitor relation C=Q/V. Can you use this to find V0? So knowing V0 and R you can find I0. And can you check your first equation? how the term -V0 exist there?
  6. n.karthick

    LRC circuits

    b) Yes you need frequency information. The supply frequency can be known from V(t)=1.414sin(1000t). Find frequency and then Z. c) You are right.
  7. n.karthick

    LRC circuits

    for (a) your answer is right. for (b) you need to find Ipeak which can be found from voltage divided by total impedance of the circuit. for (c) you know Z(=R+j(Xl-Xc) ) from this you find the phase difference.
  8. n.karthick

    Phase Angle for Simple Harmonic Motion

    As far as your first question is concerned, phase does not change if you take derivative of 'x' as long as the phase is independent of time.
  9. n.karthick

    Capacitors Network

    1) You know the relation W=1/2 * CV^2 You can find V2 because you know C2 and W2 2) Since C2 and C3 are parallel V2=V3 (Pot. diff. across C2 and C3 are same) 3) I assumed C1 is in series with C2 || C3. Q1 is known. Since they are in series total charge in C2||C3 is Q1. (In series connected...
  10. n.karthick

    Transformer concepts (magnetic induction)

    You can use both but in P=V^2/R, V is the voltage drop in transmission cable and not the transmission voltage. I prefer I^2R since if I measure the current I can find the loss.
  11. n.karthick

    Transformer concepts (magnetic induction)

    If secondary current flows (or increases) in a transformer, it creates (more) flux which is opposite to flux created by primary current. Hence the resultant flux is reduced momentarily. But the primary coil immediately draws more current from source to produce same amount of flux so that Vp...
  12. n.karthick

    Transformer concepts (magnetic induction)

    if the secondary coil is in open-circuit, the resistance of primary winding still affects the flow of current and Ip will not be 90 deg with Vp. if secondary circuit is opened, current still flows in primary and it will produce magnetic field which is responsible for Vs
  13. n.karthick

    Basic capacitor question

    Though current cannot flow through air gap/dielectric in the capacitor, charges can flow from both plates of capacitor (outwards) in to the circuit through R and V in order to charge the capacitor. So even in a DC circuit, current flows in the circuit (not through/inside the capacitor) when R...
  14. n.karthick

    Current through diode

    Yeah a,b and d are correct, but in (c), the voltage across diode and resistor is 10 v and not 15 v as you have put in the equation.
  15. n.karthick

    What is the net work done on the box?

    In real sense, however it is not possible to displace a box without doing work even at constant velocity because friction comes in to picture.
  16. n.karthick

    What is the net work done on the box?

    Yeah, your text book is correct. Even though the box is displaced from A to F, the force is at right angles to direction of displacement. So the work done is zero as you mentioned.
  17. n.karthick

    What is the net work done on the box?

    Do you mean to say that the box is not displaced at all (i.e., is it lying at the same position at the end)? Obviously no!
  18. n.karthick

    Lightbulb Brightness

    Hey, the brightness depends on the power consumed by the bulb. When bulbs are in series,yes, as you said current flow is same. You calculate power consumed by each bulb now using relation P= I^2 R from which you can find which bulb is more brighter. When they are in parallel, surely, bulb...
  19. n.karthick

    Capacitors and Power (two problems)

    for question 1: You are talking about single capacitor in your problem. So there is only one capacitance not two in your circuit even though you change size/ shape of conductors. The equation C=\frac{\epsilon A}{d} holds for single capacitor. I don't know how you are considering it as two...
  20. n.karthick

    Primary voltage and transformers

    Yes, you are correct
  21. n.karthick

    Simple circuit

    No need to know the value of resistance, because you have to find which bulb is brighter and not how much right? By simple common sense we know that the bulb with more voltage across it glows brighter. So you may check across which bulb more voltage drop will occur.
  22. n.karthick

    Simple circuit

    I assume from your question that 4 bulb connected in parallel is in series with 5th bulb to a voltage source. Now assuming all bulbs are identical, i.e., they have same resistances (say x) you can find the total resistance. And if you find voltage drop across these bulbs, you can find which...
  23. n.karthick

    RMS Voltage across capacitor

    Recall the Kirchoff's voltage law. The voltage across all elements in a loop added is zero. Here there are only three elements ( generator, resistor and capacitor). The sum of voltages across them should be zero. You know voltage across two elements. Hence it is easily to calculate the voltage...
  24. n.karthick

    Difference between voltage and voltage drop?

    No you are wrong. You cannot use V=12000V for calculating power loss P_{loss} in line. You have use the voltage drop across the line to find P_{loss}. Since we don't know that, (It is equal to difference between voltage at supply end ( V_{s}) and voltage at load end (12000V). Since we dont...
  25. n.karthick

    Electrical Voltage, a appliance problem

    You are asked to find pf on 60 Hz. You may remember that the impedance of the load Z=R+jX, where X is positive for inductive loads i.e., lagging pf and only X is dependent on frequency. Also pf=tan(X/R). Now if you change frequency of supply X changes proportionately. You know X=2*pi*f*L for...
  26. n.karthick

    Electrical Voltage, a appliance problem

    First find Z of the load using the relation P=V^2/Z. Then using the given power factor you can find the reactance X=Zsin(theta). Let this be X1. Now find new X (X2) for 60 Hz. Remember X is directly proportional to frequency for a lagging circuit since it is inductive. From X2 you can calculate...
  27. n.karthick

    Circuits and current

    In the given figure, at the node where R3 and R4 are connected (let us call this as Nd), the total current flowing out of the node through R3 and R4 is (4-2mA=2mA). Now there are two other paths joining at Nd. So the current from these two paths in to the node Nd could be 4mA ( from R1 and R2...
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