# Search results for query: *

1. ### Find equivalent resistance R in the circuit

@valhakla What circuit analysis methods have you learned? Have you covered KCL, KVL? How about mesh and nodal analysis? Perhaps delta-Y and y-delta transforms?
2. ### Final Angular Momentum of a Space Station

Is there a diagram that goes with this problem? What is the angle of the the package measured with respect to?
3. ### Series-Parallel Circuits (R/2R Ladder Networks)

Hi Lay1. I believe that your redrawing is correct, although I can't quite make out the resistor symbols. I think that R8 is the one shown here? Not sure what you mean by "passing through R8" though. There are several ways to redraw the circuit, here's an example that isn't far from the...
4. ### Determine the voltage at each point with respect to ground

Sorry, but I can't quite make out your figures in the image provided. I believe that you're trying to form the partial resistance over the total resistance for each of the points A,B,C,D? For example: If the total voltage is ##6 V##, and ##R_T## is the total resistance, then the voltage at...
5. ### Determine the voltage at each point with respect to ground

@Lay1 combined the two sources into one, so the image in the picture is okay, it just didn't mention the additional step. One way to do this problem is to first work out the total current and then use KVL around the loop, adding in the successive resistors as you go. For example, finding the...

Yes!
7. ### Energy with varying force

So, by your own words, "Acceleration is decreasing" is not correct, yes?
8. ### Energy with varying force

Consider the segment between B and C. The velocity of the cart is constant, so acceleration is zero. No work is being performed there. Next consider the segment between C and D. What happens there? Is acceleration increasing, decreasing, or constant?
9. ### Net Torque Within a Mass and Pulley System

I suspect that they're looking for the pulley's angular momentum. But since the rotation of the pulley will increase without limit (assuming ideal components without limiting factors), you might want to express the angular momentum as a function of time.
10. ### Net Torque Within a Mass and Pulley System

Your work seems correct. Perhaps, with a revision of the problem, the answer was not updated.
11. ### I Units of q in Electric Field Equation

In cgs the unit of charge is the electrostatic unit, or esu. The constant in Coulombs law is set equal to 1. Therefore, two charges each with charge 1 esu sitting 1 cm apart will feel a force between them of 1 dyne.
12. ### I Units of q in Electric Field Equation

In SI, the unit of charge ##q## is Coulombs. There are other units for other systems.
13. ### Engineering Short vs Open Circuit: Is That Correct?

Take each of the components individually. What happens to the impedance of a capacitor at ω = 0? What happens at ω → ∞? How about the inductor?
14. ### I Measuring Low Resistance: Why Meter Bridge is the Preferred Choice

Ah. According to the Wikipedia article the Post Office Box (origin UK) is in fact a Wheatstone bridge circuit.
15. ### I Measuring Low Resistance: Why Meter Bridge is the Preferred Choice

What is "post office box" (or "vox")?
16. ### Finding R and C values for an active second-order bandpass filter

I think your H(s) mixed up the numerator's R term. You wrote: R1 should be R2.

18. ### Finding equivalent capacitance

You can redraw the circuit to make things clearer. The endpoints a and b can be moved anywhere along the lines they connect to, so move them to the bottom and top points as follows: Then straighten out the bends to make the image more clear: You should be able to work out the combined...
19. ### Engineering Current Divider Circuit (Find a Resistance)

I think you'll want to take a closer look at the current divider expression. Let's say you have two parallel resistances A and B with some total current ##I## being split between them. Then you can write: ##I_A = I \cdot \frac{B}{A + B}## ##I_B = I \cdot \frac{A}{A + B}## Make sure that you...
20. ### Engineering Current Divider Circuit (Find a Resistance)

Hi @johnsmith7565 , Welcome to Physics Forums. Note that the ##60 Ω## resistor is not in series with the ##40 Ω## and ##80 Ω## resistors; The existence of the resistor ##R## precludes that. What you can say is that 20 A enters the top node from the direction of the source, and that it must...
21. ### Electric field / Gauss' Law --

How is the electric field oriented around a (long) charged rod? Is there a symmetry involved? Would you expect the field to be of even magnitude over the surface of each side of the cube? How about the sides that the rod passes through? What does Gauss' Law have to say about the total...
22. ### How to find deceleration up incline

Hi xwalsh, Welcome to Physics Forums. Have you drawn a Free Body Diagram (FBD) for the block to show the forces acting? What does it tell you about the net force acting on the block?
23. ### Find frequency such that two components have same average power

If the two voltage dividers behave identically at the given frequency, then adding equal resistors in equivalent locations will have identical results for each path.
24. ### Find frequency such that two components have same average power

If you ignore the resistors for a moment, you'll see that you have a pair of voltage dividers consisting of series-connected L and C. What can you say about the reactances of L and C if both arrangements are to produce identical potential drops at their junctions?
25. ### RL circuit after switch has been opened

Ah. That's been known to happen occasionally. It's a good thing that you checked with your prof.
26. ### RL circuit after switch has been opened

Your intuition regarding the maximum current not exceeding the initial 9 mA is correct. We also don't expect any big back-emf spikes to occur since the inductor never "sees" any abrupt open circuit conditions during the switching operation -- there's always a continuous circuit for its current...
27. ### An object oscillating in simple harmonic motion

Start with a sketch of a generic SHM and label the times of the zero-crossings:
28. ### How should I Approach this Circuit Calculation?

If the object is to find the power produced by that dependent current source, then there may be an easier way to find it than analyzing the whole circuit to find ##V_x## and ##I_x##. By inspection of the circuit, what must be the potential difference across that current source? Hint: look at...
29. ### How should I Approach this Circuit Calculation?

Just to be clear, you are looking for the power produced by the indicated current source?
30. ### Engineering Is my method of solving this correct? Superposition theorem

While at school I was introduced to several conventions for source representations. This "arrow beside a circle" was one such. The arrow is meant to represent the direction of increasing electric potential, and is not necessarily indicative of the direction of current flow. We've all seen...
31. ### Engineering Is my method of solving this correct? Superposition theorem

Your method is correct, but verify your calculation of the value for ##I_k''## .
32. ### Three phase total power consumed

@Butterfly41398 , it's very difficult to make out the contents of your images (the handwritten workings), so I can't really help spot any errors. You'll have to clean up the images to make them useful, or better yet, type out the work so that others can quote it in replies.

Correct. To summarize the situation in a diagram,

The first equation gives you the node voltage. That's fine. The second equation will then correctly give you Im. So that's fine, too. The third equation you need to be careful with the current direction of Ir. It's shown as flowing into the node, so technically: ##Ir = (0 - Vparallel)/Zr...

With the current directions you've defined in the diagram, KCL at the node would yield I am = Is + Ir, no? Note that ##i_1## flows in the same direction as Im, while ##i_2## flows in the opposite direction. So ##Im = i_1 - i_2##.

Considering that the circuit represents a generator, it is not unreasonable to find that it produces a current "out" of terminal a. I can confirm that ##Is## as labelled on your circuit diagram has negative component values as you've found. I used mesh analysis to find the currents: In the...

That looks much better to me! Well done.

Where does ##Xm## come from? You didn't list an inductance value above. I presume, given the value, that it corresponds to a 100 mH inductance? Careful here. You've used the magnitudes of the previously calculated values, losing the inherent phasor information of the complex values. Then...
39. ### Find electric field separating two charged masses suspended on strings

What is the equation for the force between two charged particles? For this problem, in which direction will it act for each particle?
40. ### Find electric field separating two charged masses suspended on strings

It would appear that you've not accounted for the interaction between the two charges. One is positive and the other negative, so...
41. ### Find electric field separating two charged masses suspended on strings

Hello jay. By forum rules you'll need to show us exactly what you've tried before we can offer help. We need to see what your current understanding of the problem is.
42. ### Confused about a Result (Circuit Analysis)

How might the polarity of the circuit's voltage source effect your results? It is unfortunate that the circuit diagram does not make it clear how to interpret the polarity of Vout where it is labelled.
43. ### Help finding Thevenim Equivalent - Circuit Analysis

Your Vth value looks good, an exact value being 25/21 V. However I disagree with the value of 10 Ohms for Rth. Consider what happens if you place a short circuit across the output. In that event Vx is forced to zero and so the current source produces zero current and the 60 Ohm resistor...
44. ### Circuits - AC circuits / phasor

You can specify ##\Phi## in terms of ##\theta## and the impedance's angle.
45. ### Circuits - AC circuits / phasor

Presumably you'll need to specify what ##\Phi## is, no?
46. ### Circuits - Transfer function of this LRC circuit

Looks good, but I think that you miscopied the constant 2 as a 3 in the final line of your derivation.
47. ### Circuits - AC circuits / phasor

Hi. It looks like you've correctly found the equivalent impedance and the magnitude of the current (both without units though). However, you'll need to account for the phase angle θ of the source in your Io.
48. ### Engineering Complex Thevenin's Circuit

In order to explore where you might be running into difficulty, perhaps you might begin by describing your understanding of the prescribed method for find the Thevenin equivalent of a circuit. For now, we assume that only fixed value sources are in play -- no dependent sources or other...
49. ### RLC Circuit Analysis -- Two sources and two switches

Your approach and results look good.
50. ### Work done by electric field to move capacitor plate

The problem doesn't directly state whether or not the capacitor is isolated or connected to a constant source voltage (to maintain a constant potential difference as the plates are moved). The relevant equation intimates that the voltage is held constant, but as it is a relevant equation and...