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.
Homework Statement
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It is required to find the current through the ammeter, marked A, in the above figure.Homework Equations
##V=iR##The Attempt at a Solution
I've redrawn the circuit as follows -
But don't know how to obtain the value ##i_3##
Homework Statement
If I have two current carrying conductor carrying current is same direction, they move towards each other so kinetiisc energy increases. So which force does work here?
Homework EquationsThe Attempt at a Solution
I know magnetic force can't do work, is work done by some...
Homework Statement
A thick slab in the region 0 \leq z \leq a , and infinite in xy plane carries a current density \vec{J} = Jz\hat{x} . Find the magnetic field as a function of z, both inside and outside the slab.
Homework Equations
Ampere's Law: \oint \vec{B} \cdot d\vec{l} = \mu_0...
Homework Statement
I am trying to figur out whether there is or isn t an Electric Field along the surface of a cylindrical current carrying wire With radius r and length L, current I and resistance R. I was trying to see if someone already asked this and i found one discussion, however where a...
Homework Statement
In Fig. 27-66, R1= 10.0 kΩ, R2 = 15.0 kΩ, C = 0.400 µF, and the ideal battery has emf E = 20.0 V. First, the switch is closed a long time so that the steady state is reached. Then the switch is opened at time t = 0. What is the current in resistor 2 at t = 4.00 ms?
This is...
I have a digital circuit , to find the energy consumed by the circuit, I am monitoring the current drawn from the supply and integrating it to get the charge pumped into the circuit ... and the total charge*V supposed to give me total energy consumed by the circuit.
But I am getting a small...
Hello all,
I've been pondering a problem with a current carrying wire in a magnetic field. The Lorentz force is easy, ILB,
with a velocity 90 degrees to the B field. So let the force accelerate the wire. Assume only one segment of the wire that has current in one direction, say up, is in the...
Homework Statement
The rotor blades of a quadcopter are 10cm long. Given that the thrust force generated by each rotor is 1N (giving a total of 4N for 4 rotors), calculate the torque () on each rotor, and the current drawn (I) from a 10V battery, given the following:
Density of air, a = 1...
Homework Statement
A square loop, side a, resistance R, lies a distance s from an infinite straight wire that carries current I (pointing to the right). Now someone cuts the wire, so I drops to zero. In what direction does the induced current in the square loop flow, and what total charge...
Homework Statement
Find io for t≥0.
Express your answer in terms of t, where t is in milliseconds.
There is no energy stored in the circuit in (Figure 1) when the switch is closed at t = 0.
Homework Equations
##x(t)=x_f+[B_1cos(ω_dt)+B_2sin(ω_dt)]e^{-αt}##
The Attempt at a Solution
Let...
I was just in a conversation with someone regarding the magnetic field resulting outside of a solid cylinder, with a current moving down the center of the cylinder, and then the resulting magnetic field after removing the current. Now I haven't thought about magnetic fields/magnets for a while...
Homework Statement
Find ##i(0^+) ## and ##i(t), t≥0^+##
Homework EquationsThe Attempt at a Solution
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I'm having trouble finding the current through this capacitor. I tried using a KVL loop for ##t=0^+##, but I'm doing it incorrectly or something.
Earlier in the problem I found...
i've built a bridge rectifier with a Zener Voltage regulator.
12V peak secondary
3300uF Capacitor
1k ohm load
1k ohm series resistor for the zener
and a 1n4728A Zener diode.
i'm getting a 2.8V steady voltage, but when i measured the current going through the load with my DMM it's measuring...
Hi Forum
I am trying to get a better grasp of the relation between electric field and the magnetic field.
The overall question is "What is The origin of selfinductance in a current loop?"
Here are my thourghts:
A battery is connected to a say circular wire with some resistance. The current...
Homework Statement
I am working on the following problem:
And ideal single phase transformer 240V/2880V is supplied with a 240V source via a resistance cable of 3ohm. If we connect a R=720ohm resistance to this, determine the primary current and the dissipated power in R.
(I'm sorry if some...
Homework Statement
i'm trying to calculate the charge operator for a complex scalar field. I've got the overal problem right but I'm confused about this:
On page 18 of Peskin, it is written that the conserved current of a complex scalar field, associated with the transformation ##\phi...
Homework Statement
Homework Equations
at point C:
i2 - i3 - i4
i2 = i3 + i4[/B]
The Attempt at a Solution
I labeled all the currents going through each resistor in the picture[/B]
for loop ABC:
2000i1 = 3000i2 + 4000i3
for loop BDC:
3000i5 = 2000i4 + 4000i3
at point C:
i2 - i3 - i4
i2...
Homework Statement
1. In Figure A-1 of Experiment 18, assume that Vdc = 8Volts, R1 = 1kOhms, R3 = 7kOhms and there is no R2 resistor. Determine the current in R1 when the transistor is fully on and carrying current. Express your answer in mA.
2. In the circuit of Figure A-1, Experiment 18...
I recently watched this Varitasium video where he explains the magnetic field due to a current carrying wire.
In the video he explains how what we see and describe as the magnetic field produced by a current carrying wire is actually just a electric force caused by the an imbalance of charges...
Homework Statement
Find the exact magnetic field a distance z above the center of a square loop of side w, carrying a current I. Verify that it reduces to the field of a dipole, with the appropriate dipole moment, when z >> w.
Homework Equations
(1) dB = μ0I/4πr2 dl × rhat
(2) r =...
Hi everyone - here's a concept that I'd like a few opinions on:
As part of a project, I'm looking at using a brushless DC motor mounted on a high-speed vehicle as a generator. Once the vehicle hits its top speed, the batteries should disconnect from the motor and the vehicle's own velocity will...
Homework Statement
I need to first find phase current in the load and line current from the supply Homework EquationsThe Attempt at a Solution
I thought it would be easier to work with a star because then the Ztl would be in series with it... I am not sure how to find the current but my best...
Homework Statement
Many experiments in physics call for a beam of charged particles. The stability and “optics” of charged-particle beams are influenced by the electric and magnetic forces that the individual charged particles in the beam exert on one another. Consider a beam of positively...
Homework Statement
I have a solenoid with a wire carrying current in the center. The wire has a radius of a, the solenoid has a radius of b. I need to find the magnetic field inside of each region. Inside of the wire, mu =/= muo.
Homework Equations
Wire B field = uo I/2*pi*r
Solenoid B field...
Homework Statement
"The switch in the circuit in the figure has been closed for a long time and is opened at t = 0. Find i(50 ms)."
I attached an image of the circuit below.Homework Equations
KVL:
Ri + q(t)/C - q(0)/C + vc(t) + Li' = vs(t)
Li'' + Ri' + i/C = vs'(t)
Where vc is voltage across...
In node analysis, after labeling the nodes. I don't know how to choose currents direction to apply KCL. it seems too complicated.. and I end up every time getting different answers the the solution sheet. I've an exam tomorrow. would be much appreciated if you could help me better understand the...
I'm a mechanical engineer by trade, but I am working on developing a testing apparatus that oscillates a neodymium magnet between two solenoids offset by by a 180 degree phase shift. Basically, one solenoid pushes, the other pulls. To get this, current is essential. I need each solenoid to get a...
< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >
in the solution sheet, He took the 18 ohms parallel with the 9 ohms and not the 6 ohms. I don't understand why he took this approach. I was going to take 18 ohms parallel with the 6 ohms and find...
Basic Question Alert ! (I need to brush up my basics and need your help)
Problem Statement: I wish to make a current carring cable loop to generate a controlled magnetic field. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html
As I understand, the magnetic field generated depends...
I am doing a series of videos on the history of electricity and I am working on a video on Volta and the first battery.
Anyway, I want to compare the voltaic pile to a typical li-ion battery running my iPhone. Now the voltaic pile could easily create 20 V of potential but it had high...
Hi, I need to calculate the current in a 400nm piece of graphene. Can some one help me please? I found online that graphene has electron mobility of 200,000 cm^2/( V s). My best attempt is as follows. Using the equation vd = uE where E is the magnitude of the electric field applied to a...
Homework Statement
The current source and voltage source in the circuit shown in the Figure below are connected in parallel so that they both have the same voltage, vs. The current source and voltage source are also connected in series so that they both have the same current, is. Suppose that...
In my physics textbook it says that ammeter in circuit C shows higher current than ammeter in circuit A and D.
And the voltmeter shows higher voltage in D than in B, and C.
It's explained in the book that way: some electric current is passing through the voltmeter in C, thus the ammeter will...
I have a silly question.
In a simple electrical circuit, we know that the two ends of the wire are connected to different potentials of a battery through the load. Potential difference causes the current flow.
But how the wire comes to know that the other end of it, is connected to different...
Greeting .
It is clear to me that the resistor represents a physical obstruction to the passing current I do not know how exactly it works and I will try to show what I was really interested in the diagram.
Homework Statement
1) what is the total resistance of this circuit between points A and B?
2) if the horizontal resistor was replaced with an ammeter what would it read if a 6V battery was placed between points A and B? let R = 20 ohms
Homework Equations
The Attempt at a Solution
had...
Homework Statement
A 2400-turn solenoid is 2.4 m long and 10 cm in diameter. The solenoid current is increasing at 1.4 kA/s .
Find the current in a 5.0-cm-diameter wire loop with resistance 9.0 Ω lying inside the solenoid and perpendicular to the solenoid axis.
Repeat for a similarly oriented...
I am trying to formulate the Current Density for a Loop of wire with a diameter,d, current,I, and an cross-sectional Area of the wire ##\pi(d/2)^2##. With spherical coordinates (radial, azimuthal, polar)
##\bar j## = ##\frac{I}{\pi(d/2)^2}*cos \theta *sin \phi \hat x##...
If a current flows in a straight wire, a certain amount of magnetic flux will be generated around it.
Now suppose I put an iron tube around the wire (but don't change the current). I know the inductance will increase, but is that because more total flux is now being generated, or is the total...
Given the circuit in the diagram I was wondering would I be able to make ib equal to the mesh i3.
I have the equation for my Super Mesh at i1 and i3 which is:
-25+30i3+5Va+20(i3-i2)+10(i1-i2)=0 (1).
The mesh i2 is equal to -2A (2).
subbing (2) into (1) gives:
-25+50i3+5Va-30i2+10i1=0 (3)...
Hello Everyone,
Could anyone please explain the difference between the conduction current density (J=σE) and the convection current density (J=ρvd)? I really appreciate any examples or applications to further elaborate these two theories.
Note: vd is the particles' average drift velocity...
Homework Statement
I am working on this problem. They start out by giving me:
I am asked to find Rref such that Vcc=8V and Icopy=0.38mA.
Homework Equations
Transistor equations
The Attempt at a Solution
In this case, they never specify if IB=0A (sometimes it does ?) but I would assume that...
Faraday's law states that emf is proportional to change in flux. The scenario I am using is a magnet is moved towards a closed loop. As it moves towards the loop, flux through the loop is increased causing a emf to be induced. Does I also know that a current is induced. So does that mean current...
Hi, so the scenario is that the primary coil of a transformer is attached to a battery in a circuit with a variable resistor. The resistor is set to the maximum resistance.
As I increase the current in primary coil by reducing resistance at a constant rate, will the current in the secondary...
For a Dipole and a Torad (or a Solenoid) I need to find the scalar Potential,phi, Charge Density,rho, and then 4-Electromagnetic Current,J(rho*c,j) where A and J are 4-vectors and a and j are 3-vectors.
-grad^2(phi) + 1/c^2*d/dt(phi) = rho/epsillon0
where grad(A(phi/c,a)) = -1/c^2*d/dt(phi)...
Hello I'm working through a book (with answers) but am struggling with voltage, current, resistance and circuits. Please check my understanding below and let me know if I've finally understood. Thank you.
In particular I'm confused in Q2
Q1. A student connects light bulbs, A and B, and...
Homework Statement
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Hey everyone, I recently got two problems on capacitance and inductance and need some help on them. Here are the two problems:
1. A Royal Red Robin Burger contains 1230 food calories. Also, more that the daily requirement for protein, fat, sodium ..., even without fries...
Hello everyone,
Recently, i have designed a capacitor bank for a company which they already have their main switch board with metering stuff. The ammeter of the main switch board has its own CTs but for the capacitor bank I need to install a CT separately. The spec of existing CTs for main...