All Questions
38
questions
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1
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Why do we indicate current to be flowing against electrons in a electric circuit ? If it is a convention thenwhy do we draw it along studying it? [duplicate]
I believe that electric current is a kind of force (even when we consider it to be opposite to the flow of electrons). If it is so then what is the nature of this force ? And also tell me if there are ...
1
vote
0
answers
47
views
Resistance across different terminals of a material of variable resistivity [closed]
I have seen many questions in my book trying to find Resistance across different materials of variable resistivity(by integration).
For example, consider the following :
I can find resistance across ...
- 265
1
vote
0
answers
75
views
How large a current is realistic for a mains wire? [closed]
I recently encountered this elementary physics question:
A mains wire outside your house is $15m$ above the ground. The power company says the voltage is $10 kV$, and the wire delivers $18 MW$ of ...
- 21.4k
0
votes
4
answers
84
views
About electric field and electric potential
We know that electric potential is the negative of work done by electric field in moving a unit charge from infinity to that place.
This statement shows that electric field causes a potential ...
- 105
2
votes
3
answers
66
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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
0
votes
1
answer
75
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Relative Amplitude: Current at full brightness [closed]
What is the relative amplitude of the flow in the filament of a miniature lamp the instant power is applied in comparison with the current at full brightness?
a. High
b. Low
c. The current is the same ...
- 11
0
votes
1
answer
89
views
What's the magnetic field produced by a current carrying circular loop at a point on its plane?
How do I find the magnetic field in this case? I already know about the magnetic field produced by a current carrying loop at an axial point or center but what about the point on its plane?
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-3
votes
2
answers
49
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What happens (from the first principle perspective) when you connect 2 negative terminals in a DC Circuit? [closed]
E is the electromotive force, r is the internal resistance.
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0
votes
1
answer
175
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Value of current in the given circuit [closed]
Since, point B is connected to Ground, Should not current exist only in the branch ABG, and zero current in the branch BCDE, as current chooses least resistive path to move to lower potential.
...
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-1
votes
1
answer
113
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Why, when an electromagnet is connected to a circuit, does the electric current not reach the required strength immediately, but gradually? [closed]
When an electromagnet is connected to a circuit, the electric current does not reach the required strength immediately, but gradually. Why?
When the battery terminals of the flashlight are briefly ...
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
2
votes
3
answers
146
views
Flow of charges
I saw this question which asks for the condition for flow of electricity through the conductor i know that electricity will flow only when there is a potential difference achieved between the ...
- 1,200
0
votes
2
answers
469
views
Direction of current flow in circuit with multiple cells
As the point $A$ is earthed we know that its potential is zero, same is true for point $B$. Due to the cell between $B$ and $C$ we can say that potential at $C$ is $-3V$. So the potential at point D ...
0
votes
1
answer
735
views
Rate of energy dissipation in a wire carrying current cut in half [closed]
In my physics textbook, I have a sample problem stated as follows:
You are given a length of Nichrome heating wire; it has a resistance R of 72 Ω. At what rate is energy dissipated in each of the ...
1
vote
1
answer
155
views
Thevenin-Norton Conversion
Using Thévenin-Norton equivalence, prove that the circuit below
is equivalent to the circuit below
The main point behind my confusion is that the current source has no parallel resistance. As a ...
- 251
2
votes
1
answer
1k
views
Can electric potential be discontinuous?
I am studying the following problem, which is 9.11 of "Modern Electrodynamics" by Zangwill.
The idea is that you have a wire attached to a perfectly conducting sphere (radius $a$) buried into the ...
- 1,544
1
vote
0
answers
159
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Electrical resistivity calculation of a cylindrical material
I have a copper rod, its diameter is 13mm, and its height is 13mm. I want to check its electrical resistivity. I have tools to give this copper a constant current by two points (the two black dots in ...
- 111
0
votes
1
answer
61
views
The equivalent resistance of the networks shown is [closed]
I solved the by taking resistance at the right side as in series but got ans as 5R/13 but the is 5R/11
- 21
1
vote
2
answers
4k
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Charge flowing through switch when it is closed [closed]
The problem that I'm having is that the initial charges would have been 300 and 600 microcoulomb on the 3 and 6 microfarad capacitors respectively. But when the switch is closed there's some charge ...
- 21
1
vote
2
answers
102
views
Charges/Current at a junction [closed]
How is current distributed into two or more wires joined to an original wire at a junction? Is there a rule that allows us to find out the current in a single wire if the currents in the rest of the ...
- 161
1
vote
3
answers
928
views
How to find the current if both positive and negative charges are moving?
A gas is connected to a copper conductor. In the gas, +6C of charge move to the left every second, and -6C of charge move to the right every second. What is the current in the copper conductor, and ...
- 254
1
vote
0
answers
48
views
Voltage difference vs number of electrons [duplicate]
When we say a battery has voltage difference, can we deduce the difference in the number of electrons at the two terminals? What does it mean to say there exists a voltage difference?
- 149
1
vote
1
answer
1k
views
Angle measurement in deriving the magnetic field of a infinitely long solenoid
I'm facing a doubt in the derivation of the magnetic field inside an infinitly long solenoid of radius $R$.
To derive $B$ all the loops in the solenoid are considered: in a lenght $dx$ there are $n\,...
- 2,617
0
votes
1
answer
127
views
How to use general expression of force between two circuits to find the force between two wires?
The general expression of the force between two circuits $1$ and $2$ with currents $i_1$ and $i_2$ and with line elements $\bf{dl_1}$ and $\bf{dl_2}$ (infinitesimal vectors pointing in the direction ...
- 2,617
0
votes
1
answer
771
views
Condition for Maximum Power in the circuit [duplicate]
Maximum Power is transferred to a load when load resistance is equal to internal resistance of source.
I want to know How ?
If I consider a source with internal resistance 'R' ,connected with ...
- 293
3
votes
2
answers
875
views
Electric field outside wire with stationary current
Consider a conductor of arbitrary structure where a stationary current flow, that is
$$\nabla \cdot \vec{j}=0$$
I did not find on textbook clear explanations on two facts:
How is the electric ...
- 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
1
vote
1
answer
416
views
How to predict length of conductor?
A long round conductor of cross sectional area $S$ is made of material whose resistivity depends only on a distance $r$ from axis of the conductor $\rho=\frac{\alpha}{r^2}$, where $\alpha $ is ...
- 209
1
vote
1
answer
945
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Resistivity - Resistance of a wire wounded closely together
Here is the question I'm facing,
The cross sectional area of a bare wire is a square of area 1.00mm^2. A 10.0m, length of this wire is wound close together on a wooden cylinder so that neighbouring ...
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1
vote
2
answers
16k
views
Why does internal resistance increase as current decreases?
Our class conducted and experiment to investigate internal resistance and terminal pd, using a cell, fixed resistor and variable resistor. The results were as follows:
As the resistance of the ...
- 361
0
votes
1
answer
148
views
charge on the capacitors
When we connecting a capacitor to a battery of $V$ volts. After it is completely charged, it is disconnected from the battery, and if we connected to another capacitor. In this case, there is no ...
- 23
1
vote
0
answers
92
views
Drift velocity in Silicon wafer
I have been asked the following question in a problem sheet:
A $100mm$ diameter, $0.5mm$ thick silicon wafer at room temperature has a charge carrier
density of $1.5×10^{10} cm^{-3}$. A potential ...
- 349
3
votes
1
answer
1k
views
Distribution of current of a rotating cone
If I have a hollow cone (surface with no bottom cover ) as the one in the picture. The cone has surface charged density $\sigma$. It rotates around the symmetry axis with an angular velocity $\omega$. ...
- 738
-2
votes
3
answers
1k
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Combination of cells
There are m*n identical cells of emf E and internal resistance r connected in parallel rows. This combination of cells is connected across an external resistance R. For what arrangement of the cells ...
- 426
1
vote
1
answer
302
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Circuits and Power [closed]
"The diagram below represents a simple circuit composed of 5 identical light bulbs and 2 flashlight batteries. Which bulb (or bulbs) would you expect to be the brightest?
a) V only
b) V and W only
...
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-1
votes
1
answer
1k
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Electric circuit question [closed]
http://www.fisme.uu.nl/nno/opgaven/bestanden/Ronde1-Theorie-2009.pdf, question 5:
You have to calculate Id when the switch at S is opened, when its
closed, the Id = 0.5 A. All resistors are the ...
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0
votes
1
answer
4k
views
Capacitance and Light Bulb And Dielectric Slab [closed]
An electric lamp having coil of negligible inductance connected in series with a
capacitor and an AC source is glowing with certain brightness. How does the
brightness of the lamp change on reducing ...
- 125
-4
votes
1
answer
196
views
Amount of 2 amperage [closed]
I have 2 equation describing the alternating amperage $I_1$ and $I_2$. I need to get amount of these amperages.
My equations:
$$I_1=10\sin(\omega t+30)$$
$$I_2=20\sin(\omega t-50)$$
How can i make ...
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