All Questions
141
questions
1
vote
2
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156
views
Why Ampère’s Law holds for infinite currents?
I'm reading Griffiths proof of Ampère’s Law and in that proof he needs to show that :
$$\oint \frac{(x - x^{'})}{\imath ^{3}}\mathbf J \cdot \mathbf {da^{'}} = 0 $$ where $$\imath = \sqrt {(x - x^{'})^...
- 105
0
votes
3
answers
343
views
On current enclosed by Ameprian loop
Ampère’s law is saying :
$$\oint \mathbf{B}\cdot \mathbf{dl} = \mu_{0}I_{inc} $$
Where $$I_{inc} = \int \mathbf J \cdot \mathbf {da} $$
But if my Amperian loop encloses a wire at an angle :
What is $...
- 105
0
votes
1
answer
1k
views
How do parallel wires attract if their force vectors point in the same direction?
I don’t understand why parallel wires with current running in the same direction attract.
Wire 1 on the left, per the right hand rule, should cause wire 2 to experience a leftwards force. Wire 2 on ...
- 3
12
votes
6
answers
2k
views
If voltage is same in two points why does electron move? [duplicate]
We know that at point A and B there is same voltage.Then why electron moves from one point to the another one?
- 315
-1
votes
1
answer
113
views
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
0
votes
1
answer
85
views
Which electron moves first if you connected a wire to both ends of a battery at the exact same time?
Question 1:
Which electron in the circuit moves first if you were to connect a wire to both ends of a battery simultaneously?
Is it:
The last electron in the wire, which is pulled into the cathode of ...
- 101
1
vote
0
answers
33
views
Drift velocity of electrons how electrons drift
When no external electric field is applied, electrons move with thermal velocity and return to their initial position so displacement is zero. However, when an external electric field is applied, ...
- 11
1
vote
1
answer
584
views
Why current density is defined as the rate of change of current with respect to area ($\frac{di}{dS}$)
What I know is current density is the amount of current passing per unit area perpendicular to the current. But then why do we define it as the rate of change of current with respect to change in area ...
- 155
1
vote
0
answers
92
views
Is magnetic field a consequence of electric field? [duplicate]
We know that magnetic field is produced by a current carrying wire with time varying current? My doubt is that- do the electrons in motion cause the magnetic field or is it due to some another reason?
- 806
2
votes
1
answer
232
views
Why do the turns of an electromagnet repel one another?
I'm trying to understand electromagnets and the relationship between magnetic field and current. Just thinking about a loosely wound coil, with an air core. Something on the wiki page "...
- 21
3
votes
3
answers
235
views
What do $\ell$ and $A$ precisely mean in the formula for electrical resistance?
The formula for resistance is
$$R=\rho\frac{\ell}{A}$$
Generally in most of the textbooks it simply written that $\ell$ is the length of the conductor and $A$ is it’s cross-sectional area. But my ...
- 155
1
vote
1
answer
52
views
Bridge full wave rectifier more smooth signal [closed]
This is a full wave bridge rectifier:
The waveform of the full wave bridge rectifier is this :
But I want a more smooth signal which will remind less of an AC. If I put an inductor with a resistor ...
user268802
1
vote
2
answers
1k
views
Two charged spheres connected by a wire
I have a few doubts about this problem. So we have two charged spheres of radius $r_1$ and $r_2$, one is initially charged with a charge $Q$, while the other one is initially without charge. The ...
2
votes
1
answer
447
views
How does electric field propogate in a wire? [duplicate]
When I say electric field, I'm referring to the electric field that causes the movement of charge in the wire.
I have learnt about currents and resistances, but I have never really had an ...
- 669