All Questions
54
questions
0
votes
0
answers
31
views
Current sensitivity in transformer scheme with SQUID
I've tried to determine the maximum current sensitivity in this transformer scheme but I'm not sure if my solution is valid. I need to find the relation between the current in the input transformer ...
0
votes
1
answer
35
views
What does "90 degrees ahead of phase" mean in inductance problems?
I've been working on this homework problem and I have determined that the induced EMF on the right coil is sin(x-90). However, I do not understand what "ahead of phase means." When I graph ...
- 101
1
vote
2
answers
123
views
How to compute the resistance of a nonuniform cylinder with varying resistivity?
The generally quoted formula foe resistance is
\begin{equation}
R = \rho \ell/A
\end{equation}
some special cases are easy to solve. For example the case where the current flowing along the z-axis and ...
- 196
0
votes
1
answer
34
views
How to find the capacitance between two metal sheets [closed]
Let’s say I have two metal sheets in a 2D plane. The first one has area A, the second one is infinitely long, and they are separated from each other by a distance d. How can I find the capacitance ...
0
votes
0
answers
29
views
Non-standard circuit
I partially solved this problem.
Problem: A charged sphere of radius $a$ is connected through a resistance $R$ to the earth. An electronic flow breaks out towards the sphere of infinity at speed $v$ ...
4
votes
1
answer
63
views
Why In the following $RL$ circuit, the connection to $b$ must actually be made an instant before the connection to $a$ Is broken? [duplicate]
In Resnick halliday, student 10th edition page - 795. In the topic current decay in RL circuit, the following statement is used, the connection to b must actually be made an instant before the ...
- 43
0
votes
1
answer
124
views
In The question given below, why the length for calculating reluctance is taken by those dotted lines?
The question is as follows:
For the core shown in Fig. 3.20, it is required to produce a flux of 2 mWb in the limb CD. The entire core has a rectangular cross section of 2cm × 2cm. The magnetizing ...
- 31
1
vote
1
answer
80
views
Physics HL IB 2008: Transformer currents question
A question on the IB HL Physics paper of a couple of years back looks like this:
In the second image, taken from this video solution, you see that the given answer should be D.
Now, I have an issue ...
- 319
2
votes
1
answer
854
views
What will happen to the bulb of the circuit after closing the switch? [closed]
Say it connects a bulb with the circuit below, with the switch $S$ open. Every cable has negligible resistance and the battery has no internal resistance.
What happens to the brightness of the bulb ...
- 23
0
votes
3
answers
486
views
What is the formula for total reactance?
Total Reactance is the sum of capacitive reactance and inductive reactance. So, it should be given by the formula
$$X = X(L) + X(C) \, ..$$
However, in some sources it is
$$X = X(L) - X(C)$$
Which one ...
user355398
1
vote
1
answer
181
views
What happens if a charged capacitor is connected to the ground on both sides through resistors? [closed]
Imagine we have the circuit below:
When the switch is connected to (a), we will be charging the capacitor. After the capacitor is fully charged, the left side of capacitor will be at 5V and right ...
- 113
0
votes
1
answer
106
views
How to find current density given resistor, and voltage, using Ohm's law in this case?
I was wondering about how to find current density, given a resistor and an electromotive force.
resistor's data are: resistivity = $\rho$, length = $l$, and cross sectional area = $A$.
resistor = $\...
0
votes
2
answers
340
views
How much can we push the plates of capacitor?
I am currently a highschooler and came across this question in physics
A capacitor of plate area $A$ and separation $d$ is connected to battery of emf $V$ and is charged to steady state. Now the ...
- 3
2
votes
3
answers
66
views
How does the actual power of the device depend on the angular frequency of the voltage? [closed]
The voltage source produces a sinusoidal AC voltage. An electrical device with resistance and inductance is connected to the source. How does the actual power of the device depend on the angular ...
user331916
1
vote
0
answers
412
views
Capacitance of a thin conducting ring
I am following an exercise in which the capacitance of a thin ring is computed. The ring has radius $b$ and thickness $2a$ where $a<<b$.
In this exercise they compute the potential due to a ...
- 735
1
vote
1
answer
49
views
Energy loss in a circuit during critical damping [closed]
I would like some intuitive explanation regarding impedance in an $RLC$ circuit.
So far, my understanding has been limited to underdamping situations where both resistance and reactance are present.
...
- 81
1
vote
1
answer
147
views
Is the closed contour integral of the Lorentz's Force equal to charge * EMF of the circuit?
I have a situation as pictured
That is, a rotating rectangular spire subject to an uniform magnetic field $\vec{B}$ (The rods to which it is attached and make the system spin is non-conductive, so it ...
0
votes
1
answer
89
views
Induced emf of a moving rod with certain velocity
I am calculating the emf of a moving rod with velocity $v$, given $v$.
My approach is to multiply
$$Blv$$
Where $l$ is the width and $v$ is the rate of change of the length.
But then I found out ...
- 103
1
vote
1
answer
351
views
Square loop above a wire with a current running through the wire [closed]
A rectangular loop is above a wire with a current running through it. If the loop is connected to an external circuit, what is the EMF generated by the loop to the circuit? There's a bit more to it ...
- 31
0
votes
1
answer
313
views
TV Channel Frequency Range Question [closed]
This is a simple texbook problem: A television channel is assigned the frequency range from 54 MHz to 60 MHz. A series RLC tuning
circuit in a TV receiver resonates in the middle of this frequency ...
- 71
0
votes
1
answer
201
views
The self inductance of the motor of an electric fan is 10 H. In order to impart maximum powr of 50 Hz, it should be connected to a capacitance of [closed]
how can i solve this
(*)The self inductance of the motor of an electric fan is 10 H. In order to impart maximum powr of 50 Hz, it should be connected to a capacitance of
what is the concept behind ...
- 15
4
votes
1
answer
184
views
Can Faraday Law be applied to a loop with some twists and turns in it?
Consider the above question. I have been able to solve the question understanding area vector of A and B are opposite in direction.
However I have some conceptual doubts.
In Faraday Law, when we say ...
- 1,568
1
vote
2
answers
3k
views
Transformers: How does current in primary coil change?
I was doing a question on transformers and found this really confusing question:
A 100% efficient transformer converts a 240V input voltage to a 12V
output voltage. The output power of the ...
- 11
0
votes
1
answer
121
views
Why the Vout vs. VR graph looks like an oval loop?
So we've performed an experiment about the resonance angular frequency and RLC circuits in the lab.
I understand that the phase of voltage on the inductor and the voltage on the capacitor are equal in ...
- 51
0
votes
1
answer
37
views
Change in ammeter's indication due to change in resistance [closed]
I stumbled on a problem in a textbook, where I was asked to describe the change in ammeter's indication due to change in resistance in circuit: rheostat's slider is moved or key is locked as indicated ...
0
votes
1
answer
59
views
Kirchhoff laws - parallel RLC
I'm having a hard time understanding why would the current flowing through the resistor in the following diagram be the sum of the currents "beside" the two AC sources.
I know the sum of ...
- 1,038
0
votes
0
answers
21
views
Relation between transformers and the resistance
I have to create a circuit where i change 240V AC into 6kV DC. The amount of Amperes that comes out of it is 30mA. Following Ohms law, would that mean I need 20,000 Ohms resistance to be able to use ...
0
votes
2
answers
101
views
Inductor in a DC circuit [closed]
I found this question,
I don't understand how could the current through 2R ,immediately after opening the circuit, be less than when the circuit is closed!
Shouldn't be an emf from the inductor that ...
- 3
4
votes
2
answers
321
views
Induced Currents in Circuits
I was given the following question:-
The plane figures shown are located in a uniform magnetic field directed away from the reader and diminishing. The direction of current induced in the loops is ...
- 220
0
votes
3
answers
2k
views
Powering an electromagnet for a long duration
Looking to power an electromagnet requiring 12 DC volts at 4 Watts, and wondering what size battery I would require to do this for 4 weeks?
My maths so far is, and I am not sure this is correct:
<...
- 1
2
votes
0
answers
1k
views
Finding the voltage across an inductor when opening the switch [closed]
Well, I've the following circuit:
In the circuit I want to find the voltage $\text{V}_{\text{Y}_1}\left(t\right)$ as a function of time, after I open the switch (this switch was closed 'forever' ...
- 21
1
vote
2
answers
137
views
Current in the inductor at $t=0$
$L_1 = 5H, L_2=0.2H, M=0.5H, R_0=10 Ω$, and $i_g=e^{-10t}-10 A$. I need to find $i_2$.
I've started with DE
$$i_2R_0+L_2(di_2/dt)+M(di_g/dt)=0$$
and solved it for $i_2$, so $$i_2=0.625e^{-10t}+Ce^{-...
- 111
0
votes
0
answers
281
views
Exponential fit in Origin doesn't converge
I am using a data treatment program called Origin, wich I think many of you are familiar with. The data I have is time vs voltage in the resistor of an RL circuit.
The expression that describes the ...
0
votes
2
answers
218
views
What happens to a system of capacitors when a dielectric is inserted into one of them?
sorry for my English.
While doing some homework I've stumbled upon this "circuit":
the system is connected to the same potential difference through a generator that is connected to points A ...
- 55
6
votes
3
answers
1k
views
Physics olympiad question about a charge capacitor
This is problem 1463 from the Russian magazine Quant.
Unfortunately my Russian is not good enough, so I apologize if the translation of the problem contains errors.
Problem. Inside a flat charge ...
- 417
-2
votes
1
answer
294
views
Finding the current in a light bulb [closed]
I am doing this practice problem where it asks me to find the current through the light bulb at two different temperatures. The problem I am having is that I cannot find out how to do the problem with ...
- 111
0
votes
2
answers
23
views
Magnetic energy in coil at time $t$ after circuit being hooked up
"A coil with inductance L = 50 mH and R = 600 ohm is coupled in series with a resistance R = 200 ohm to a battery with the voltage 12 V. How great is the magnetic energy in the coil at the time t = ...
user180617
0
votes
1
answer
629
views
Transformer universal EMF equation derivation
At this Wikipedia page, we've that the 'Transformer universal EMF equation' looks like:
$$\text{E}_{\text{rms}}=\frac{2\pi\times\text{f}\times\text{n}\times\text{a}\times\text{B}_{\text{peak}}}{\sqrt{...
- 291
0
votes
1
answer
248
views
How to derive and write Kirchoff loop law for circuits including capacitors?
Consider a circuit like the one in the picture
Where $V_0$ is an electromotive force.
How do I write Kirchoff "loop law" for circuits like the one in picture (i.e. with capacitors)?
Here is the ...
- 2,617
2
votes
2
answers
2k
views
Faraday's law in circuits with multiple loops and different magnetic fields
I'm confused about the application of Faraday's Law in to situations with a circuit made of two loops that enclose two different changing magnetic fluxes.
Which of the two is correct?
The emf in each ...
- 2,617
0
votes
1
answer
107
views
Will there be any current induced in a purely capacitive circuit?
Will current be induced in a purely capacitive circuit if a magnetic field B is present perpendicular to it and a movable conducting wire completing the circuit is moving with a velocity v.
Just want ...
2
votes
1
answer
1k
views
How do I show for an ideal transformer $M^2=L_1L_2$?
I've been stuck on this problem for about an hour.
In an ideal transformer, the same flux passes through all turns of the primary and of the secondary . Show that in this case $M^2=L_1L_2$, where $...
- 5,371
1
vote
1
answer
640
views
Faraday's Law: Current loop and proton
A single circular loop of wire with radius R carries a large clockwise current I(loop)=I0, which constrains a proton of mass M and charge e to travel in a small circle of radius r at constant speed ...
- 21
2
votes
1
answer
1k
views
Current in an RC circuit inside in a magnetic field
Does my question make any sense?
Context: The capacitor is charged with charge $Q_0$. There is a magnetic field $B=B_0 \hat{z}$ perpendicular to the monitor's screen. The length of the (AB) wire is $\...
- 365
2
votes
0
answers
42
views
ODE envolving current [closed]
I have to do this exercise:
9. The current $I(t)$ at time $t$ flowing in an electric circuit obeys the differential equation
$$I''(t) + RI'(t) + I(t) = \sin \omega t$$
where $R$ and $\...
- 21
1
vote
0
answers
632
views
Voltage in a lossless transmission line
I have a question where I'm deriving expressions for different variables within a lossless transmission line. Here's the question as posed:
Consider a lossless transmission line of characteristic ...
- 113
1
vote
3
answers
1k
views
Current through two inductors after a long time
I'm having trouble with visualizing the following problem, which is asking me for the final, steady current in both inductors $L_{1}$ and $L_{2}$. I was thinking that after a long time, essentially ...
- 111
1
vote
0
answers
463
views
Different phase in capacitively coupled RLC circuits
I was trying to work with some data for a lab report I'm writing about capacitively coupled RLC circuits.
The setup is pretty simple and looks like that:
Where $C^{'}$ is the coupling capacitance.
I ...
- 125
0
votes
1
answer
947
views
Voltmeter Question [closed]
I understand that a voltmeter is used for measuring potential electrical difference, but how exactly should said voltmeter be connected with the resistor in circuit?
- 55
2
votes
3
answers
8k
views
Magnitude of magnetic field at the center of circular wire
I'm preparing for an exam by solving the sample questions , here is the one I'm having difficulty with :
Following is the given circuit.
Which contains two resistance
$R_1$ and $R_2$ in form of ...
- 421