A measure of the rate at which electric charge is transported (especially through a circuit), it has units of charge/time.

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30 views

Comparing voltages of Parallel and Series circuits

There are two electric circuits. Resistor 1 ($R_1$) connected with resistor 2 ($R_2$) by series circuit $R_1$ connected with $R_2$ in parallel Each of the circuit has battery with emf and the ...
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1answer
25 views

Current in Parallel Circuits

For the parallel circuit below: Why is the current across the ammeter unchanged when the resistance of the variable resistor is increased? I've always learnt that current varies in parallel and ...
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1answer
61 views

What is fatal? Current or voltage? [duplicate]

I have been searching this answer for quite a while. I asked my physics teacher and he said it is current that causes death. A friend of mine, who is a EE student, and his answer was voltage. When i ...
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2answers
56 views

Speed of electrons in resistors

What affects the speed of electrons in a resistor? If two resistors are connected in series, they both have the same current; same number of electrons passing at a point per second. Suppose one ...
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0answers
21 views

Standing Wave ratio vs frequency in power transmission lines? [migrated]

What is the relationship between Voltage Standing Wave Ratio (VSWR) and frequency in context of transmission power lines?
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3answers
316 views

Why does my measured I-V curve for a film of aluminum suggest high resistance?

I plotted the I-V curve between two points (few microns apart) on a thin aluminum film. I expected this metal to be a conductor and have a much lower resistance, but the slope suggests that it is ...
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1answer
37 views

Why we take mean of squares in RMS Current instead of taking mean of absolute value of current? [duplicate]

I know $I_{\text{rms}}$ produces the same energy over time as if the current were DC. I am asking the reason why it works. The main focus of this question is highlighted below which makes it different ...
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1answer
62 views

What really happens in a electric circuit?

How do electrons behave in an electric circuit? There was a question before about a voltage drop which was interesting, but I can not participate in that discussion, so I am writing this question ...
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1answer
39 views

Getting Deep into Drift Velocity

We know for a metallic conductor Current $\frac{I}{enA} = v$ where $v$ is drift velocity , $e$ is the charge of an electron, $n$ is no of electrons per unit volume and $A$ is area of cross section. ...
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1answer
61 views

Why high voltage transmission lines?

This is a question which I seem to have tackled multiple times, solved each time after reading a dodgy internet explanation, then partially forgotten about and retackled half a year later. It is time ...
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2answers
45 views

What is the potential difference across the lamp? [closed]

For all problems, assume that the battery voltage and lamp resistances are constant, no matter what current is present. A 75-W lamp is connected to $125 V$. What is the current through the lamp? ...
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0answers
16 views

Nichrome wire, resistance properties

Nichrome wire is often used as resistance wire, because it's got a high melting point (around $1400^\circ C$) and resists oxidation well. If you pass a current through a Copper wire, it's got a very ...
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1answer
81 views

Is the physics of $j = \rho v$ questionable? What are the consequences? [closed]

In electrodynamics you have the quantity $\mathbf{j}$, which represents density of current per surface area. It is often said that $\mathbf{j} = \rho\mathbf{v}$, for geometric reasons. When I make ...
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3answers
60 views

Is there charge build up before a resistor?

I understand that Kirchhoff's current law says that the current, $I$, is constant throughout a resistor, i.e. there is no build up of charge in a resistor. All charge going in to the resistor is the ...
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0answers
18 views

Finding the current in the circuit [closed]

I don't understand the logic of finding a current. I think I can find it using nodal analysis or mesh analysis, but I want to understand the method. Here is an example: I want to find $I_0$.
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0answers
25 views

Could you explain me how 'I*dl x r' from Biot-Savart Law works for finite long wire?

http://cnx.org/contents/416f27b6-e016-47c5-b1f1-01f470fd2907@10/Magnetic_field_due_to_current_ I am studying this problem right now but can't move forward. Biot Savart law shows that ...
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1answer
38 views

Exact Relation between voltage and current [duplicate]

I apologize before hand if this seems too naive. I'm having a really tough time understanding the relation between voltage and current. I read that 1 Volt is the amount of work done to move a $1As$ ...
3
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2answers
55 views

What causes a resistor to heat up?

In the following video clip at 2:10, http://www.youtube.com/v/YslOUw5oueQ , Professor Walter Lewin talks about a misconception people have that the energy going through a wire to a resistor is in ...
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1answer
23 views

Magnetic interaction of wire and rectangular loop

In this video, Prof. Lewin shows an infinitely long wire and a rectangular loop at a distance $r_1$ from each other, each carrying a current. He then calculates the magnetic field resulting from the ...
4
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1answer
80 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 ...
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1answer
25 views

What is the magnetic field on surface of a current carrying conductor?

Biot Savart's law says there should be none as the current element is along the displacement vector, hence as $\sin \theta = 0$, so, the magnetic field must be zero. But, as per Ampere's loop rule ...
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1answer
62 views

Does alternating current come from DC?

I wonder whether alternating current is produced from DC current or whether AC and DC are entirely different concepts. Is there any relationship between AC and DC?
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3answers
93 views

The Difference Between voltage and current

I know that this question has been asked many times before, and I have read over several of the threads asking this question, but they do not include the gripe I have with my problem of understanding ...
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1answer
25 views

Transmission lines…which one is high? potential or potential difference?

The electric potential at generating station is 11,000 V...why such high potential is generated there? From generating station it is transferred to local station...is there any electric potential at ...
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0answers
65 views

Is ohm's law violated in electric transmission lines?

Electricity is generated at a very high voltage say, 11,000 V... Does that voltage refer to the potential difference across the transmission line or does it refer to the electric potential at the ...
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2answers
49 views

Is it possible for electrons to carry more than one charge?

Sorry if this has been asked before. Could also be a really basic question (new to electrical study). I am a bit confused about the relationship between electrons and charges. So what I understand is ...
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1answer
18 views

Can a current source provide Voltage to a resistor?

We know that the tension between a perfect current source is 0 We have Va-Vb= 0 but we also have by ohm's law Va-Vb=RI=5V so 5 = 0?
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1answer
39 views

Photoelectric effect stopping potential

$q_eV_s = hf - \phi$ My question is... suppose we are testing the photoelectric effect. One plate is illuminated. We have applied the stopping potential. Suppose an electron leaves one plate with $KE ...
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1answer
21 views

Variation of Peak Current and Peak Voltage with Capacitance in an AC circuit

The relation of Peak current, Peak voltage and Capacitive Reactance in Alternating Current is given by: $$i_m=\frac{v_m}{X_c}$$ and $$X_c=\frac{1}{C\omega }$$ So if we have a circuit with a ...
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0answers
74 views

Photoelectric effect Experiment - What's the voltage bias of the set up?

What's the bias of the setup? Forward / Reverse? I'm doing a photoelectric effect experiment.The experimental setup involves a photocell, which has an emitter (cathode) Potassium and a ...
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3answers
181 views

Is it possible to prove conventional current is always equivalent to actual current?

I understand how the conventional current is logically equivalent to the actual current of electrons in a circuit. However, whenever I'm studying some new concept, and things are assumed as working ...
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1answer
21 views

Foucault currents with a simple pendulum

I have this diagram : It's a kind of pendulum; when it swings, it passes through a small aera where there is a magnetic field. Therefore, the electrons moves towards the bottom because of a Lorentz ...
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0answers
15 views

Mechanism of Current flow in Metals [duplicate]

I do not fully understand the mechanism of current flow in conductors. It cannot be that a current starts only when an electron from one terminal of the electric supply physically reaches the other ...
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0answers
28 views

Propagation of Error Formula

I did a lab, and found the Hall voltage for different currents. From these, I was also given the direction, and magnitude of the magnetic field. I need to find the number of charge carriers per ...
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0answers
27 views

Alternating current means alternating voltage?

We get supply from an AC generator which provides AC current.It is by the way the generator works that the current is alternating. Because of electromagnetic induction and the fact that the coil is ...
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3answers
71 views

Electron flow in a wire [duplicate]

How do electrons that constitute a current flow move in a wire? Some say it's like a wheel.If you give it a push,every part of the wheel moves instantly. Is that what happens to electrons?Do they ...
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0answers
24 views

Strength of Magnet in Magnetic Bearings

While reading about magnetic bearings, one reads about passive/active magnetic bearings. By passive, one means no electric current is put into the bearing for attaining magnetic levitation/flux. In ...
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1answer
99 views

Using Ampere's Law without Right-Hand-Rule to derive an expression for the magnetic field around a current

I'm a little confused over the textbook example of applying Amperians to get the magnetic field around a current. I understand we take a loop which shares the rotational symmetry of the wire (a ...
1
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1answer
53 views

2 simple Generators = Im lost (intensity) [closed]

What happens? we have 2 Generators and 2 intensities, when I2 and I3 come together (they have opposite sides ) what happens? I tried writing down the voltage relations but I'm stuck because I don't ...
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3answers
79 views

How can there be a voltage when there is no current?

I'm told at school that the Electromotive Force (e.m.f) of a battery equals the potential difference between the terminals of the battery when there is no current. How is that possible? How can there ...
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0answers
29 views

Magnetic flux and flow of electrons

What does change in magnetic flux mean? How can you change magnetic flux? How does a change in magnetic flux influence a current of electrons (electricity)?
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2answers
28 views

Direction of current in concentric cylinders

Example 7.2 in David Griffiths E & M book (3rd edition) has a side view of 2 concentric cylinders, with smaller radius $a$ and larger radius $b$. The region in between $a$ and $b$ has ...
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2answers
56 views

Why is Lightning referred to as High frequency source?

Lightning strike is categorized as DC because of its electrostatic nature. The negative flash/stroke is found to have 200KA of current with a voltage close to 300KV (cloud to ground). But why is it ...
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6answers
227 views

Do electrons flow only on the surface of a wire?

Since the $\vec{E}$ field inside a "perfect" conductor is zero, do the electrons(the current) flow only on the outer surface? This has bothered me since I studied electromagnetism. Thank you for ...
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1answer
77 views

Ampere's circuital law for finite current carrying wire

When I was studying about Ampere's circuital law. Then there comes a question in my mind that "whether this law is applicable for finite current carrying wire or not"
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1answer
44 views

Why does a motor draw more current stopped or under load? [duplicate]

I have a small motor connected to DC source, and use the ampere meter to survey the current through the motor. While the motor is rotating, I hold the motor by hand so that it stop. I see the current ...
0
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1answer
55 views

Would a 9v battery be able to produce gas bubbles by water electrolysis at 1000 meters?

I'm currently working on an underwater robot and was hoping to use the gas bubbles for buoyancy control .
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3answers
57 views

Energy stored in a capacitor

Suppose we have a capacitor connected in series with a resistor and this is connected to a cell. So would the voltage across the capacitor be less than the the emf of the cell? And hence the energy ...
2
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2answers
60 views

relation between current,voltage and resistance

i want to know the relation between voltage,current & resistance , apart from this ohm's law V=IR.Because in zener diodes,current does not increase accordingly with the voltage.At BREAKDOWN POINT, ...
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1answer
67 views

How is Magnetic force on a current carrying conductor $Blb$

I was reading an answer about torque acting on a rectangular current carrying loop kept in a uniform magnitude field B. Force acting on each sides is $F_1$, $F_2$, $F_3$, $F_4$. It's written here : ...