# What is Electric current: Definition and 172 Discussions

An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In a electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons.The SI unit of electric current is the ampere, or amp, which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit Electric current is measured using a device called an ammeter.Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conductors, they cause Joule heating, which creates light in incandescent light bulbs. Time-varying currents emit electromagnetic waves, which are used in telecommunications to broadcast information.

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1. ### I EM field and EM wave

Hello, I'm new to this forum. I have a short question that I can't solve on my own, I've consulted many books but I can't find solutions, I hope you can help me. Then considering a conductor traversed by an electric current that varies over time, it produces an electromagnetic field, under...
2. ### I How does the velocity of electrons depend on the voltage across a conductor?

How exactly (what is the function?) the velocity of the electrical conductor's electrons depends on the voltage of the conductor?
3. ### Two concentric conducting spherical shells and resistor in between

The first thing I thought about was the relationship ##\vec{J}=\frac{\vec{E}}{\rho_r}## which is a statement of Ohm's law. That is, current density is proportional to electric field and the constant of proportionality is the reciprocal of resistivity ##\rho_r##, which is the same as...
4. ### I Question about the current through a strong insulator

Suppose we put a strong insulator under our feet. In this case, when we connect the test light to the electrical outlet, the light of the test light lights turn on. I wonder how the electric current can pass through the strong insulator. If we calculate, the electric current cannot be more than...
5. ### I Do electric currents depend on the frame of reference?

Suppose you have an infinite straight wire carrying electric current I. If you move in the direction of the electrons (opposite to the direction of the current) at the drift speed, would the current be zero in your new reference frame? Why or why not?
6. ### I Resistance and specific resistance relationships

I'm using a four-probe system (nextron) to measure the voltage between the two points of my sample. Sample has a cylindrical shape and it's placed on its base inside the instrument. The probes are placed on its upper surface (the base of the cylinder). From the voltage measured, I'd like to...
7. ### Engineering Current density calculation in anisotropic ferromagnetic film

Hi everyone! First time posting here, so I apologize in advance for any bad formatting. I am working on a mathematical model of an anisotropic magnetoresistive sensor. The central part of such a device is a Wheatstone bridge that consists of four current-carrying ferromagnetic (FM) films, the...
8. ### I What causes the magnetic force in a uniform magnetic field?

As is well known, when electric current flows in a straight wire, a charge in motion in the vicinity of the wire, parallel to it, is affected by a force called the magnetic force, which is attributable to the relativistic contraction effects that the wire undergoes in the frame of reference of...
9. ### I Why does resistance reduce current in whole circuit?

Ohm's law states that current is inversely proportional to resistance, but on the quantum level, why does that actually slow the current down for the whole circuit? In all of the basic explanations, it talks about how the more densely packed matter in the resistor creates more collisions and...
10. ### I Angular momentum associated with a current carrying circular wire

How should I calculate the angular momentum carried by a current carrying circular wire? Is it correct to consider the angular momentum of the electrons moving with drift velocity? Like ##L = n m_e v_{drift} r## where ##r## is radius of the loop, and ##n## is total number of electrons moving in...
11. ### How does Earth Ground "absorb" electric current?

This is a topic that almost no one can actually explain from what I found on the internet. This answer https://physics.stackexchange.com/questions/74625/does-alternating-current-ac-require-a-complete-circuit/74999#74999 is the closest I found so far. The idea is how the grounded neutral...
12. ### Do electrons flow through a battery or is it something else?

This is a confusing question. I am not sure if electrons flow through the battery from positive terminal to negative terminal against the electric field within the battery; or the electrons deposit on positive plate resulting in a chemical reaction that releases electrons at the negative plate...
13. ### I Energy flux direction in a conducting wire?

On the Internet, I have read that the energy doesn't flow in the wire, for example in a very simple electric circuit made of a battery and a closed loop. When one computes the Poynting vector ##\vec S \propto \vec E \times \vec B##, one gets that its direction is towards the center of the wire...
14. ### Finding a good descriptive model of the electric circuit (for 8th graders)

Since this quesstion popped up in this thread I thought it might be better to create a new thread: https://www.physicsforums.com/threads/a-question-about-an-electrons-movement-in-a-dc-circuit.997736/ The question is the following: What kind of descriptive model could/should one use while first...
15. ### How Do Kirchhoff's Laws Help Calculate I1, I2, and I3 in a Circuit?

According to the circuit in the figure; Can you calculate the values of the currents I1, I2, and I3. Can you send me a detailed solution to understand?
16. ### How can electrons flow all the way through the circuit?

Electric currents and the things within are generally explained through the help of intuitive water current examples, where potential difference is explained through the pressure difference and electric current is explained as the flow of water. But I like to think in terms of some driving force...
17. ### Electric dipole moment vs electric current dipole moment

I have to estimate the electric dipole moment of an NV center in units of Am. I know that for a regular electric dipole moment it can be estimated using p=ed. With e=1.6*10^-19 and d=0.1 nm (interatomic distance), this however is in units Cm. I don't know how to go to Am
18. ### Electric current is not a vector while electric current density is a vector

Why is electric current not a vector while electric current density is a vector? What's the intrinsic difference between the two through that surface integral?
19. ### Electric Current and Resistance

I have attached my solution to this problem but I think I got the wrong answer.
20. ### Inducing electric current in a wire (a comparison)

Consider the following experiment: from a lacquered copper wire we cut off twenty to thirty pieces of about 10 cm. From them we form a bundle of parallel wires and connect the two ends with one more wire each. The other ends of these two wires are connected to a sensitive analog ammeter. We hold...
21. ### What happens when electric current is distributed in the material?

When supplying electricity to the material. the shape of the material may or may not be square. This material may be This material may be moisture materials or solid materials that may conduct electricity. I would like to know the travel characteristics of electric currents and the potential...
22. ### Electric current and resistance question

Homework Statement:: problem solving You build a wire by combining an 8 inches copper wire with a 10 inches nichrome wire. If their combine resistance is 10 kΩ, find the cross section area of both wires. The nichrome wire has twice the area of the copper wire. Homework Equations:: I = V/R...
23. ### Electric current and resistace problem

This is a problem I have been strugglying since I don't know if I should work it together or apart I ask my teacher and I don't know if I listened well but he told me to use the combine resistance and substract it with the restistance of the material. You build a wire by combining an 8 inches...
24. ### Electric current being alternated with continuous part

Summary: In which scenario a current may exhibit alternated and continuous character together? Hi All, I would like to know in which scenario an electric current may exhibit alternated and continuous character? Something like $$I(t) = I_0 \sin (\omega t) + I_1$$.
25. ### Why is resistance of similar cases calculated differently?

Homework Statement 1.In the WE-11 resistance is calculated by integrating and that too by taking length as dr and area as the CSA of the small cylinder .. Shouldn't length be l and area by 2πrdr..? I also don't understand why can't we simply use Dl/A formula , Where A =π((2R)^2 - R^2) 2)...
26. ### I Why is Displacement Current Excluded from Four-Current?

To put this in another way, is there some reason from first-principles as to why we have j as the spatial component of the four-current rather than the total current density which includes the displacement current? Has anyone tried to see what the experimental consequences of this would be? Kevin M.
27. ### Symmetry in Electrical Circuit Analysis

How is symmetry used to solve electrical circuits? I have seen several problems in books in which currents in two resistors are said to be equal due to 'symmetry'. That is a concept that I fail to understand and thus cannot apply. In class, we were shown a few circuit diagrams which were...
28. ### Electric current flowing in a power transmission line

A cable of resistance 12 Ohm carries electric power from a generator producing 250 kilowatt at 10,000 volts. Calculate the current in the cable. Solution using P=VI I=25A but using P=I^2R 250000=I^2×12 I =500/root 12 Amps What is the reason for the different...
29. ### An electric current in a wire occurs when....

An electric current in a wire occurs when... A. electrons move in the wire as a result of getting pushed along from a neighboring electron. B. electrons move in the wire as a result of the repelling force from the negative battery terminal and the attractive force from the positive battery...
30. ### UV light + electric current = boom?

Hi, so I was hoping to get an EE's explanation for what just happened. So my son was apparently over by the light switch pointing a UV pen light at the switch. Suddenly there was very loud, gunshot-like pop, sparks flew, and I had to go reset the breaker. Maybe correlation doesn't imply...
31. ### Find the current I in this electrical circuit

Homework Statement Homework Equations V = I.R The Attempt at a Solution 6 ohm and 3 ohm are series = b Then b pararel to 9ohm = c = total resistance b = 9ohm c = 9/2 ohm I = V/R I = 9.6/c I = 2,13 A Can you help me? Is it right? My friend's answer is 0,8
32. ### Conductivity of an electrolyte

I know that electric conductivity of metallic conductors increases with decrease in its absolute temperature(kelvin) . But is it the same for electrolytes such as water. Is cold water a better or worse conductor of electricity than warm water at same pressure and concentration.
33. C

### What are the difference between electrical current and RF?

Hi. This might be really basic. But I am really struggling to grasp the difference between electrical currents such as AC and DC and RF. For the case of AC current, it alternates currents at a certain frequency.. which makes me wonder how AC and RF are different. Also, if you could, could you...
34. R

### Electric Current and Potential Difference

when the external electrical potential difference is applied across the conductor ,electrons flow in the direction opposite to the current.Whether the number of free electrons in the conductor decrease?
35. ### Can quantum mechanics be used to explain electric current in materials?

Electric current can be studied using classical electromagnetism. In that case, the explanation is that there is a net flow of free electrons through a wire, say. Looking more close on the situation, what happens is that there is a difference on the energy level of some atoms and electrons can...
36. ### Calculate resistance if the switch is closed 2 battery with different voltage

Homework Statement before that, can you tell me about "current flow in this circuit" if : A. the switch is open B. the switch is closed the Question is No. 1 Calculate the resistance of R if the value of the current I in the figure is 0.50 A. ( i think it is related to no 2) no 2. Calculate...
37. ### How does electric current flow through a conductor

There's been a discussion going on since this following thread: Range of frequency of electromagnetic wave how electric current flow through a conductor. I need a proper clarity, does the electrons literally displace and flow or just the disturbance/energy travel through conductor making...
38. ### I Show me how terms with Q disappear

The general Ampere force law equation given by Maxwell is: According to Maxwell, all terms containing function ##Q(r)## will vanish after closed integration w.r.t. ##s'## because they will get reduced to functions of ##r## and the upper and lower integration limits will be same since the...
39. ### AC Current in GHz Frequency and Zero Resistance

Hello Experts, I am a physics newbie with big ideas. I have a question. I am thinking about how to produce a zero Resistance Current. We know we can do this using super-conductors in sub zero temperature, but maybe there's another way. My assumptions (which could be wrong): 1) Resistance in a...
40. ### Electric Current of an Orbiting Electron

Homework Statement The question is based on the Bohr model with an electron with charge e and mass m orbiting a proton about a circular radius r. I have to find k in the equation I = e2 / sqrt kε0r3m where k is a some combination of constants. Homework Equations Coulumb's force law: F =...
41. ### Understanding Ohm's Law: Electric Current & Potential Difference

According to Ohm's law, "Physical conditions remaining the same, the electric current flowing through a conductor is directly proportional to the potential difference across the two ends of the conductor" I have two conceptual queries: FIRST When the ends of the conductor are not connected to...
42. ### Will any charge flow through the circuit?

https://drive.google.com/open?id=0B3IenBvKWb4PZW9rRWg4cXptT2c I had to find the resistance of this circuit between A and B. My teacher said that since the blank wires have zero resistance, the potential difference across the ends of the blank wire is zero(according to v = ir) and thus 1,4 are...
43. ### Spreading of electric current -- start signals in a circuit

Hi I have a question about current start signals in a simple circuit such as explained in http://amasci.com/elect/poynt/poynt.html. Turning on a switch somewhere in the circuit, sphere of influences, i.e. motions of electrons in wire and generation of Poynting vector around the wire, start from...
44. ### Electric field of electric current

Does electric current also produces electric field (in addition to magnetic field) at a typical stationary point? In other words, electric current includes the moving charges. Do these charges produce electric field at a stationary point? Or, does the electric field of these charges come into...
45. ### 220V 50Hz Equipment vs. 230V 60Hz Equipment compressor

If If you have a compressor designed for US 60 HZ 230 V what are the risks with applying it in 220 V 50 HZ ? I understand there will be a ~20% derate in power but are there any safety or failure concerns ? would the lifespan of equipment change? Do I need a transformer ? This equipment...
46. ### The value of electric current on a sinking conductor

Homework Statement A flat capacitor formed by two square plates of side 0.3 m which are 2 mm apart. Source keeps voltage 250 V on the plates. What current flows between the plates and the source if the condenser is immersing in kerosene at velocity of 5 mm / s? The relative permittivity of...
47. ### Some questions on terminology (for native English speakers)

Hello! I am a beginner in English terminology. I know that direct current is a flow of electricity that moves in one direction only (i.e. does not change its direction). I also know that alternating current is an electric current that reverses direction at regular intervals. However, I cannot...
48. ### Proving an expression / help with defining electric current

Homework Statement http://imgur.com/AotzH28 Two long, straight conducting wires with linear mass density λ are suspended from cords so that they are each horizontal, parallel to each other, and a distance d apart. The back ends of the wires are connected to each other by a slack,low-resistance...
49. ### Electric current is reduced by the resistance?

How does the current is reduced by the resistance. How is the rate of charge flow decrease in the whole circuit if the variable resistor is placed in the middle of the circuit?
50. ### Is Electric Current a Scalar, Vector, or Constrained Vector?

what is electric current...a scaler or vector?? ...well I personally believe that it is somewhere in between the two extremes (what is not 0,need not be an 1 either :oldbiggrin: ) ...particularly because of the strange similarity we see in vector addition and phasor addition)...some people...