Questions tagged [electric-current]

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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47 views

How can the Neutral wire be 0V if its AC? [duplicate]

So I understand Alternating current like a battery, in which the Poles are constantly changed out, so the circuit stays completed, but the electrons change directions. But how can then in an AC plug ...
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Is there even a slight transient current when a piece of wire is connected to a single terminal of a cell?

Suppose I have a cell/battery , both the terminals are at non-zero potentials.If I connect a piece of wire to say the negative terminal will there be some sort of electron redistribution in the wire. ...
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Isn't Kirchhoff's junction law a violation of conservation of charge?

As a beginner of classical electrodynamics I am quite confused in understanding Kirchhoff's junction law or it may be the reason that I misunderstood the law of conservation of charge.Please correct ...
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If current through a resistor is zero, does the circuit break?

I'm really confused. I'm studying about how capacitors are charged, and I learnt that there's a resistor attached in series with the capacitor when it is being charged. When the capacitor is fully ...
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Charging capacitor in an incomplete circuit [closed]

I have 2 confused questions regarding the below circuit. please help me out How will the capacitor even charge in the following scenario when the right side of the capacitor is not connected to ...
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Question about current density

I was looking at past exam papers and found a question that I can't understand. It is basically about current flow but the diagram is really confusing me. The diagram is the following: The question ...
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Proof of Ohm's Law [duplicate]

I was watching MIT OCW 802 and the lecturer mentioned that Ohm's law has a proof by quantum mechanics. Can someone please explain this.
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What is the current in a short linear antenna in an alternating $E$-field?

Consider a short linear wire with some low but non-zero resistance, such as a copper wire. If this wire is then placed in an alternating electric field that is oriented parallel to the wire, the field ...
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Will the volt, ampere, ohm or other electrical units change on May 20th, 2019? [duplicate]

When watching a video by Veritasium about the SI units redefinition (5:29), a claim that the volt and unit of resistance (presumably the ohm) will change by about 1 part in 10 million caught my ...
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Evaporating tungsten wire

Consider an incandescent bulb having a thin filament of tungsten that is heated to high temperature by passing an electric current. The hot filament emits black-body radiation. The filament is ...
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What is the cause of resistance?

I searched for this question on the internet but didn't got a satisfactory explanation. What I thought on the topic is that the cause of resistance is 'the effective nuclear charge'. The nucleus ...
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Current Divider rule

If you have two resistors $R_{A},R_{B}$ connected in parallel with a battery, you can find the current that flows through one resistor ex.$R_{A}$ using the current divider rule: $$I_{A}=\frac{V_{T}}{...
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How does resistance affect the voltage drop? [closed]

There is a series curcuit and there are 5 resistors in it which are the light bulbs. I know that current is directly proportional to the voltage and inversely proportional to the resistance. Can ...
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1answer
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Induced EMF in an inductor

In the above figure, the circuit is closed for a very long time and is then opened. It is stated that "the emf across the inductor just after opening will be very high so as to oppose the change of ...
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Thermal Energy in a Conductor

We know that thermal energy developed in a current-carrying resistor is given by $U=I^2Rt$ and also $U=VIt$. So my question is- Should we say that $U$ is proportional to $I$ or $I^2$
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Intuitively, why is the net current through a volume $0$ if the current is steady?

Say I want to find the total current passing through the following volume, provided by Griffiths' textbook on Electromagnetism. It's not the most useful image, but perhaps imagine the inner curved ...
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What is the Electron Flow in a wire with 2 power sources 180 out of phase?

If you took two independent power supplies and set them to a sine with each power 180 degrees out of phase. The powers supplies will share a common line and the load will be equal_____________? Do ...
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Direction of the current and the electrons [duplicate]

If the electric current is defined as Coulomb/second, why is the direction of the current is just the opposite of the direction of the flow of electrons?
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At null temperature (0 Kelvin), is the current going through a diode (PN junction) null?

At null temperature (0 Kelvin), is the current going through a diode (PN junction) is null, for a positive voltage in a direct polarisation, above the built-in voltage of the depleted region ? If ...
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What should be the independent variable in a resistance experiment?

I was asked a question by a student today and I have been pondering about it for a while now. In an experiment to measure resistance of a conductor, should we vary voltage across the conductor and ...
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Why is a net flow of positive charge in one direction equivalent to a net flow of negative charge in the opposite direction?

If I understand correctly, conventional current was defined with reference to positive charges because it was found that a negative charge flowing in one direction is actually equivalent to the same ...
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How does the $I$-$V$ curve for bulk metal look like?

For semiconductors, the current (I) vs. voltage (V) relationship is as shown in the picture below. As we increase the applied voltage, the electron-hole pairs generate increases too, so we see an ...
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Size of electromagnet needed to replicate Earth's magnetic field

I guess the title says it all. How big of an electromagnet would you need to generate a magnetic field the same as Earth's? Like, what kind of amperes are we talking here? (Assuming a hypothetical ...
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Kinetic energy and current

When a battery is connected to a resistance circuit, we know that it loses energy because heat is emitted as a result of the collisions between the electrons and stuff, but my question is, is the ...
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Why isn't $V_L$ not equal to $i_LR_L$ according to Thevenin's theorem?

According to Thevenin's Theorem $I_L= \frac{V_{th}-V_L}{R_g}$ whereas $I_L$= current through the load. $V_{th}$= The potential difference across the load resistance when the load resistance is ...
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What *exactly* is electrical current, voltage, and resistance?

I am taking AP Physics right now (I'm a high school student) and we are learning about circuits, current, resistance, voltage, Ohm's Law, etc. I am looking for exact definitions of what current, ...
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Direction of magnetic field around a straight current carrying wire

I am currently studying for O Level and I have been learning about electromagnetism for the past year. The topic has never clicked for me because I've never been taught the true relationship between ...
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Proper utilization of Ampere’s Law

I am tasked with finding the magnetic field due to a bus bar, which seems to have the exact same set up as Problem 7.62 in the fourth edition of Griffiths' textbook on Electrodynamics. To which I ...
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Relationship between concentration and resistance of aqueous solutions

I'm a senior physics/chemistry student working on a practical assignment where I am trying to identify the resistance of CuSO4 in solution (distilled water). I have recorded my data and determined it ...
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What happens when very high resistance is connected parallelly with low resistance

$1.$What happens when a resistor of very high resistance (say $10,000 \Omega $) is connected in parallel with a resistor of comparatively lower resistance of about (say $100 \Omega $)? Is the ...
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Why is high voltage dangerous?

High $V$ low $A$ electricity is transformed into low $V$ high $A$ through a step down transformer for safer use in homes. But how is it any safer? The wattage is the same for the pre-transformer ...
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Does the electric current inside a wire fluctuate when the wire shape is changed while still having it connected to the terminals?

The electric current inside a wire depends on the electric field across the infinitesimal segments that the wire consists of. If we readjust the shape of the wire, i.e. make changes to the conducting ...
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What causes the magnetic field around a wire? [duplicate]

According to maxwell’s equations, a magnetic field is caused by a changing electric field, but where is this changing electric field in the context of a current carrying conductor that has an induced ...
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Will electricity follow a path of least resistance on a rotating conductor?

I would like to know if electricity will follow a path of least resistance on a rotating conductor. Please reference the drawing below. This is showing a rotating non-conductive disc with a strip of ...
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What will happen if an ideal current source is connected to a isolated resistance?

I know that ideal current source is a theoretical thing. But when it comes to solve problems we have to consider these scenarios. Now suppose an ideal current source is connected with an isolated ...
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Classical Explanation for Electron-Ion collisions

Classically, electrons collide with other electrons and massive (by comparison), stationary positive ions as they conduct down a wire when an electric field is applied. Is there a good mechanism ...
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Current law explained

Kirchhoff's Current Law (KCL) is experimentally proven but what exactly happens?. I have made a model by taking the drude model and adding the interactions between the electrons and the reason why ...
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Electric current doubt

How to find out the direction in which the magnetic needle of a magnetic compass aligns itself when kept beside a current carrying conductor?
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Temperature of an annealed palladium wire in air

I'd like to estimate the temperature of a palladium wire that undergoes annealing by electric current in air. A simplified scheme is shown here: My first guess was to apply the Joule-Lenz formula: $...
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What's the electric and magnetic field of an infinite long annular wire with constant current density distribution?

Suppose we have an infinite long annular wire, with constant current distribution equal to $J_z=\delta(r-r_0)$. What is the electric field in $r,\phi,z$ directions and the corresponding magnetic field?...
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Divergence of current density and electric field within a wire

In the following exercise: I concern myself with the validity of my interpretations of (b). Here I am more confident slightly. The divergence of the current density is merely $- d \rho / dt$, so as ...
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Deriving magnitudes for $\mathbf J$ and $\mathbf E$ from the shape of a conductor

In the following exercise: I have no idea how to infer the magnitude of $\mathbf J$ nor $\mathbf E$ given the shape of the wire. The only clear thing to me here is that A, B and C all have different ...
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Formula for total current and phase angle in function of given currents and phase angles in the branches of a parallel RLC circuit

Consider this parallel RLC circuit powered by an sinusoidal alternating voltage and two branches, one containing an ohmic resistance $R_1$ and a capacity $C$, the other one containing an ohmic ...
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How electric current flows through liquids and gases?

i know in liquids there are electrolysis. But are there time limit in electrolysis ? I think because the ions go and connect slowly to electrodes, and when there are no ions in the liquid, the curent ...
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How does electricity travel near the speed of light if electrons drift at a snail pace? [duplicate]

I was in a reddit argument with someone who said electrons didn't flow at the speed of light in a circuit. Then he linked the Wikipedia page for drift velocity and defeated me in one fell swoop. Now, ...
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Orientation of resistor when connected in a cicuit [closed]

Consider a cuboid shaped resistor. Now Case1: Connect the resistor along is length to a battery. Case2: Connect the resistor along is breadth to a battery. In the two cases the length and cross-...
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How would this circuit behave? [closed]

A function generator is hooked up to two resistors in series. The voltage across the function generator changes over time, shown by the different graphs The questions ask to find the output voltage ...
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Resistance and temperature relationship

When the temperature changes from $\theta_1$ to $\theta_2$, having $\alpha$, and the amount of resistance ($R_1$) in the previous temperature ($\theta_1$), we can calculate $R_2$, the amount of ...
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Detection of surface potential change

So if I have a large metal plate with a small electric current in it and the plate makes contact with a small metallic rod. Since the surface of the metal plate slightly changed, will I be able to ...
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Why does current always go to the resistance which is lower? [duplicate]

Why does current chose the easy way? Is there a proper mathematical formula about why current tends to go over a resistance which is smaller?