What is Faraday's law: Definition and 266 Discussions
Faraday's law of induction (briefly, Faraday's law) is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon known as electromagnetic induction. It is the fundamental operating principle of transformers, inductors, and many types of electrical motors, generators and solenoids.The Maxwell–Faraday equation (listed as one of Maxwell's equations) describes the fact that a spatially varying (and also possibly time-varying, depending on how a magnetic field varies in time) electric field always accompanies a time-varying magnetic field, while Faraday's law states that there is EMF (electromotive force, defined as electromagnetic work done on a unit charge when it has traveled one round of a conductive loop) on the conductive loop when the magnetic flux through the surface enclosed by the loop varies in time.
Faraday's law had been discovered and one aspect of it (transformer EMF) was formulated as the Maxwell–Faraday equation later. The equation of Faraday's law can be derived by the Maxwell–Faraday equation (describing transformer EMF) and the Lorentz force (describing motional EMF). The integral form of the Maxwell–Faraday equation describes only the transformer EMF, while the equation of Faraday's law describes both the transformer EMF and the motional EMF.
Homework Statement
A 22.0-cm-diameter coil consists of 20 turns of circular copper wire of 2.6 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, changes at a rate of 8.65 x 10-3 T/s. Determine (a) the current in the loop, and (b) the rate at which thermal energy...
1. I have encountered a problem on power extraction in Faraday's Law application. Consider I live out in the country and I suddenly realized that a power line of current I=I0cos(2pi*60t) [A] is situated 20m from my farm. A copper wire of diameter 4.1mm, 200 m in length was found in the garage...
Can anyone verify that I'm thinking about this situation correctly:
among cyclists, there exists a thing called a roller trainer, which allows cyclists (or anyone who wants a workout) to train indoors (eg when it's too cold out). It looks like this...
(As magnitudes)
Faraday's law states that induced emf in a conducting loop by a changing flux, say x, is:
emf = dx/dt
Now if we have a circuit with the loop in series with wires (which are then tied together), how do I picture the voltages/currents in this circuit?
I mean, the actual...
Homework Statement
According to the Faraday's law of electrolysis, does the mass given as a result indicate the total difference of the masses of both the anode or cathode, or just one electrode?
Thank you
Homework Equations
The Attempt at a Solution
Homework Statement
Actually this is not exactly a homework. I am trying to understand the following situation only.
Consider a ring shaped coil of N turns and area A. Connect it to an external circuit with a twisted pair of leads ( this info is trivial). The resistance of the circuit...
Homework Statement
A circular loop of radius r = 12cm is in a uniform magnetic field B=.5T w/ its plane normal to the direction of the field. If the magnitude of B then decreases at a constant rate of -.01T/s, at rate should r increase so the induced emf in the loop is zero?
Homework...
Hello,
I have found this information on the internet, but just need a few parts explained:
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/farlaw.html
For the 'magnet moving into coil' (lower left illustration),where it says ^B/^t=0.4T/s (where '^' is the triangular symbol in the...
1. Homework Statement
A coil of 15 turns and radius 10cm surrounds a long solenoid of radius 2cm and 1x10^3 turns/m. The current in the solenoid changes as I = (5A)sin(120t). Find the induced emf in the 15-turn coil as a function of time.2. Homework Equations
emf = -Nd[flux]/dt
\Phi =...
Homework Statement
For the situation described in Figure P31.32, the magnetic field changes with time according to the expression B = (8.00t^3 - 4.00t^2 + 0.800) T, and r2 = 2R = 5.00 cm.
Figure P31.32
(a) Calculate the magnitude and direction of the force exerted on an electron located at...
A figure has a 3.0T magnetic field that is normal to the plane of a conducting, circular loop with a resistance of 1.5 ohms and a radius of .024m. The magnetic field is directed out of the paper. The area of the non-circular portion of the wire is considered negligible compared to that of the...
Homework Statement
A 26.4 cm diameter coil consists of 23 turns of circular copper wire 1.90 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, changes at a rate of 8.00E-3 T/s. Determine the current in the loop.
Part Two: Determine the rate at which thermal...
faraday's law states that if there is a change in the magnetic flux inside a conductor, a potential is induced across the ends. Is the opposite also valid, i.e. if I have a current carrying conductor with a constant potential applied across the ends, will there be a change in the magnetic flux...
Faraday's law is ∫ E dl = - ∂Ф/∂t
if we take sqaure root on both sides,
√∫ E dl = √- ∂Ф/∂t
√∫ E dl = i √ ∂Ф/∂t
Now the r.h.s has "i" in it. Does this mean anything? Having "i" in a equation means anything?
I have seen "i" in schrodinger equation and dirac equation. As like those...
Homework Statement
A magnet is suspended so that it is free to swing above a coil that is connected to a power supply. A pointer has been attached to the magnet so that a small swing of the magnet will result in a large deflection of the pointer. When there is no current through the coil, the...
Homework Statement
Eliza connects a power supply, switch, and a multimeter (in ammeter mode) in series with a wire coil. The wire coil is held into place by 2 connecting wire leads. One of the wire leads has been stripped off of the insulating enamel coating so that half the wire is bare; the...
My question is about the system in the picture. There is an upwards force which acts on the ring. My problem is that I don't see how it comes about. I mean, suppose that at time t, the current through the coil flows counterclockwise and is increasing. So there is an increasing, upward pointing...
Homework Statement
Hi guys, I've recenlty done Faraday's law of induction in my AS physics class. I am really not understanding why it works. I get the Maths that's fine (PS were not doing integrals etc, were only doing the maths which invlove say given areas etc), but I don't see why its so...
Using Faraday's law for a closed loop we say that the EMI is -d(phi)/dt .Now this emf is induced in the closed loop...So between which two points is the PD equal to -d(phi)/dt
Thanks
Homework Statement
A conducting rail in contact with zero-resistance conducting wires is pushed with constant speed, causing an induced current of 0.69A. Using Faraday's Law, calculate the rail's speed if the wires are separated by 0.34m.
B = 0.50T
R = 2.0Homework EquationsMagnetic Flux =...
The answer to this question (attached gif) is supposed to be "E".
I can get bL^2/R if I just compute the flux and differentiate to
compute the induced voltage and current, but how does one
figure out that it goes counter-clockwise. Also I'm at a loss to
explain why whatever effects the field...
Hi,
I'm having some troubles with Faraday's law of induction:
\mathcal{E} = - {{d\Phi_B} \over dt}
I don't understand the meaning of the minus. I do understand that, according to the law of Lenz, the induced current is directed such that it counters the change in magnetic flux. But I...
I got a master degree in physics and I still found that this is difficult to expalin Faraday's law of induction within the context of special relativity. Most of the textbooks I found only shows that Maxwell equations are consistent with Lorentz transformation. Those books do not really derived...
[SOLVED] faraday's law
Homework Statement
A uniform magnetic field \mathbf{B}(t) in the z-direction, fills a circular region in the x-y plane. If B is changing with time, what is the direction of \mathbf{E}/
Homework Equations
The Attempt at a Solution
My book says it is...
Hey everyone, I'm having trouble with b and c and any help would be appreciated! I attached two pictures on the bottom (one of the entire problem and one of just the diagram)
Homework Statement
Five loops are formed of copper wire of the same gauge (cross-sectional area). Loops 1-4 are...
Homework Statement
A 100-turn, 2.0-cm-diameter coil is at rest in a horizontal plane. A uniform magnetic field away from vertical increases from 0.50 T to 1.50 T in 0.60 s. What is the induced emf (in mV) in the coil?
Homework Equations
\Phi_m = ABcos\vartheta
E = \frac{d \Phi}{dt}...
Homework Statement
A radio antenna that receives an AM radio station that emits at 800 kHz is constituted of an inductor of 120 turns with a radius of 0.6cm. The inductor is home to an iduced emf du to a magnetic field oscillating from the radio wave. The magnetic field is...
[SOLVED] Induced emf: Faraday's Law and Lenz's Law Question
The plane of a conductive loop with an area of 0.020 m^2 is perpendicular to a uniform magnetic field of 0.30 T. If the field drops to zero in 0.0045 s, what is the magnitude of the average emf induced in the loop...
hello,
i'm wondering where this law comes from. I'm currently reading Feynman's lectures. I skipped some parts but i don't think it says where it comes from. does anyone here know of a link, a book or the part in Feyman's lectures which mentions the origin of it? i know Maxwell's equations have...
[SOLVED] Faraday's law problem
Homework Statement
Charge Q is uniformly glued over a thin (insulating) ring of radius R and mass m.The ring can rotate freely in horizontal plane about z axis.A magnetic field B is switched on along +z axis.The ring rotates with angular velocity w.
(A)w=0...
Faraday's Law: Conservation??
Hi there
There seems to be a few related posts on this topic but I can't make sense of them.
In the integral form, I think that Faraday's Law says that round-trip path integral of electric field is equal to the negative temporal rate of change of magnetic...
Ok so we are studying Faradays law right now and am a little confused. I will try and state my understanding of it, please correct of wrong.
If we have a change in magnetic flux in a certain area in space there is an induced current. This current must obvoiusly come from an electric field...
Homework Statement
A coil of 15 turns and radius 10cm surrounds a long solenoid of radius 2cm and 1x10^3 turns/m. The current in the solenoid changes as I = (5A)sin(120t). Find the induced emf in the 15-turn coil as a function of time.
Homework Equations
emf = -Nd[flux]/dt
d[flux]...
Homework Statement
Take a loop of wire with a radius of 2.0 cm. A B field is perpendicular to the area enclosed by the wire. If the field is reduced to zero from 0.55 T in 0.25 s, what is the induced emf between the ends of the wire?
Homework Equations
B=Magnetic Field
A=Area
Flux=...
Consider a copper disk rotating with constant angular velocity, as shown in the figure. A bar magnet is directed normal to the surface of the disk, as shown in the following figure:
If a galvanometer is used to measure the induced current in the outer rim of the disk, a nonzero induced...
Homework Statement
A wire loop of radius 0.3m lies so that an external magnetic field of magnitude 0.30 T is perpendicular to the loop. The field reverses its direction, and its magnitude changes to 0.20 T in 1.5s. Find the magnitude of the average induced emf in the loop during this time...
I don't really understand how Faraday's Law can be one of Maxwell's equations if it doesn't seem all that fundamental to me.
An induced emf/voltage is created by the rate of change of magnetic flux with respect to time in a closed loop.
Well obviously if a voltage is induced it means an...
Homework Statement
A conducting bar of length L = .218 m and mass M = .08 kg lies across a pair of conducting rails. The contact friction between the bar and the rails is negligible, but there is a resistor at one end with a value R = 20.0 Ohms. Initially the rod is given an initial speed of v0...
Lenz's and Faraday's Law Induction. Help on resistor and switches!
Homework Statement
Find the direction of the current in the resistor shown below a) at the instant the switch is closed b) after the switch has been closed for several minutes and c) at the instant the switch is opened...
Magnet through Loop (Faraday's Law??)
A constant magnetic field passes through a single rectangular loop whose dimensions are 0.35 m 0.55 m. The magnetic field has a magnitude of 2.1 T and is inclined at an angle of 50° with respect to the normal to the plane of the loop.
(a) If the magnetic...
According to faraday's law of induction "Whenever a conductor is moving in a magnetic field a current flows through it"
the question is "How the magnetic field get converted into current ? "
How the MMF get converted into EMF ?
No mathematical eqn's please.
your explanation should be...
induced emf!
Hello,
I am studying magnetic induction, induced emf, and faraday's law, that sort of thing. My book gives an example where the magnitude of a B-field is increasing at constant rate through an axis of a circular coil with N number of turns and a certain radius r, find the...
A piece of copper wire is formed into a single circular loop of radius 13 cm. A magnetic field is oriented parallel to the normal to the loop, and it increases from 0 to 0.50 T in a time of 0.45 s. The wire has a resistance per unit length of 3.3 10-2 /m. What is the average electrical energy...
A coil containing N = 550 turns with radius r = 3.90 cm, is placed in a uniform magnetic field that varies with time according to B=(At + Bt^4), where A = 1.05 \cdot 10^−2 {\rm T}/{\rm s} and B = 3.00 \cdot 10^−5 {\rm T}/{\rm s}^{4}. The coil is connected to a resistor of resistance 640 Ohms...
Hello, I'm stuck (again) on a physics problem.
The problem:
Early in 1981 the Francis Bitter National Magnet Laboratory at M.I.T. commenced operation of a 3.3 cm diameter cylindrical magnet, which produces a 30 T field, then the world's largest steady-state field. The field magnitude can...
I've got some serious problems understanding Faradays law.
I think any changing magnetic field will create/induce an electric field through empty space. Is that correct? And if so, what is the direction of the field? I mean, the electric field vectors must have *some* direction, but I can't...
Here is a question I have on a practice exam that I am having a littel trouble with.
A plane loop of wire consisting of a single turn if radius 5cm is perpendicular to a magnetic field that increases uniformly in magnitude from 0.5T to 2.5T in 1.5 seconds what is the resluting indiced current if...
A magnetic field is perpendicular to a 0.060 m 0.060 m rectangular coil of wire that has 100 turns. In a time of 0.070 s, an average emf of magnitude 1.5 V is induced in the coil. What is the magnitude of the change in the magnetic field?
My professor has not covered this in lecture yet, but...
The drawing shows a copper wire (negligible resistance) bent in a circular shape with a radius of .5 m. The radial section BC is fixed in place, while the copper bar AC sweeps around at an angular speed of 15 rad/s. The bar makes electrical contact with the wire at all times. The wire and bar...
I was wondering about the following problem:
You are looking down on a single coil in a constant magnetic field B = 0.9 T which points directly into of the screen. The dimensions of the coil go from a = 6 cm and b = 15 cm, to a* = 20 cm and b* = 19 cm in t=0.028 seconds. If the coil has...