Emf Definition and 939 Threads

i once read a book which says that EMF wave are form due to changing of current which result in electric fields and result in changing magnetic field and repeated in infinite loop :smile: i also heard that visible light (which is also a EMF radiation) is produced due to the changing orbit of...

If there is a circuit with--Emf -5V and one 5ohm resistor and one 20 F capacitor, what is the current of the circuit? Will there be any effects on current because of capacitor?

If there is a circuit with--Emf -5V and one 5ohm resistor and one 20 F capacitor, what is the current of the circuit? Will there be any effects on current because of capacitor? :smile:

Electromagnetism -- induced EMF Please help :) I'm just trying to grasp the whole ... induced EMF concept ... please, anyone?! Also ... breaking the field lines?

A motor is designed to operate on 117 V and draws a current of 12.2 A when it first starts up. At its normal operating speed, the motor draws a current of 2.30 A. Obtain (a) the resistance of the armature coil, (b) the back emf developed at normal speed, and (c) the current drawn by the motor at...

The coil of a generator has a radius of 0.14 m. When this coil is unwound, the wire from which it is made has a length of 5.7 m. The magnetic field of the generator is 0.20 T, and the coil rotates at an angular speed of 25 rad/s. What is the peak emf of this generator? Please help me get...

A magnetic field is given in the xz-plane by B=Bo/x j Wb/M^2. Consider a rigid square loop situated in the xz-plane with its vertices at (Xo,Zo), (Xo,Zo+b),(Xo+a,Zo+b) and (Xo+a,Zo). If the loop is moving in that plane with the velocity V = V_{o}\vec{i} m/s what is the induced emf using...

Hey, I'm in a high school AP class and am stuck! Can anyone help me with this problem concerning induced emf? I would surely appreciate it. There is a loop of wire, shaped like a square. Each side is 20 cm long. There is a magnetic field directed into the page. What would be the way of...

Hey, I'm in a high school AP class and am stuck! Can anyone help me with this problem concerning induced emf? I would surely appreciate it. There is a loop of wire, shaped like a square. Each side is 20 cm long. There is a magnetic field directed into the page. What would be the way of...

A long solenoid has n = 400 turns/m and carries a current I = 30 A(1 - e-1.6t/s). Inside the solenoid and coaxial with it is a loop that has a radius R = 0.06 m and consists of N = 250 turns of wire (Fig. 3). What is the emf induced in the loop? I know that the inuced emf is N(deltaBA/deltat)...

I been trying to work out these problems for the past two days but cannot come up with a solution. If anyone can help that would be greatly appreciated. 1) A 3.80-g bullet moves with a speed of 180m/s perpendicular to the Earth’s magnetic field of 5.00 X 10-5 T. If the bullet possesses a net...

if someone could help me with understanding the basics of Lenz's law and Motional emf i'd really appreciate it. I'm having some trouble applying it to questions that were assigned.

A 14.2m long steel beam is accidentally dropped by a construction crane from a height of 9.53m. The horizontal component of the EArth's magnetic field over the region is 16.4 uT. What is the induced Emf in the beam just before impact with the earth, assuming its long dimension remains in a...

A circular loop of radius 17 cm is located in the plane of the paper inside a homogeneous magnetic field of 0.7 T pointing into the paper. It is connected in series with a resistor of 131 ohm. The magnetic field is now increased at a constant rate by a factor of 2.2 in 15 s. Calculate the...

A 7.2 cm diameter loop of wire is initially oriented perpendicular to a 1.3 T magnetic field. It is rotated so that its plane is parallel to the field direction in .20 s. What is the average induced emf in the loop? A = πr2 A = π*.001 = .004 m ФB = BA = (1.3T)(.004m) = 5.2E-3 Wb...

Hi,, A small circular loop of radius a and Resistance R is kept Coplanar and concentric with a large circular loop of radius b,a<<b.The large loop is kept fixed in space and a constant current I is sent through it.Now the small loop is rotated with a constant velocity w about a...

I don't see the point why EMF is maximum when the Area vector is at a 90 degree angle with the magnetic field (B) I know that when you consider the equation EMF = NBAw sin(wt) it will show an oscillation with the max when sin(wt) = + or - 1 but when I think about it... according to...

emf induction... Why does a moving conductor becomes induced with an emf? Well I know it has to do something with changing magnetic flux. The thing I want to know is why the changing magnetic flux leads to e.m.f. induction? Secondly, we have an A.C. generator in which the coil is rotated to...

Here is a bonus question that I was given yesterday. I am completely at a loss of what to do. Any suggestions? A conducting loop with a half circle of radius r=0.20m and 3 straight sections. The half circle lies in a uniform field B that is directed out of the page. The magnitude of B as a...

What must the emf E in the figure be in order for the current through the 7.00 - Ohm resistor to be 1.81 A? Each emf source has negligible internal resistance. I solved for I through the 3-ohm resistor using the outer loop: 24V - (1.81A)(7-Ohm) - (3 Ohm)(I) = 0 and got that I = 3.77. I...

I have problem with a circuit. It has two sources of emf, and I'm not sure how to calculate the magnitued of the current in the circuit due to this. Here's what the circuit looks like (R's are resistors, *'s are just for spacing): |----------+|1|------| |*************** | R = 5...

Hello, I don't know if you will find this question silly or not because I know it shouldn't be that hard but for some reason I keep getting it wrong. Here it is: A square copper loop, with sides of length 10.4 cm, is located in a region of changing magnetic field. The direction of the...

A closely wound, retangular coil of 80 turns has dimensions of .25m x .4 m. The plane of the coil is rotated, in .06 sec from a position where it makes an angle of 37 degrees with a magnetic field of 1.1T to a position perpendicular to the field. What is the average emf induced in the coil...

I was wondering just how possible it is to "steal" electricity by inducing an EMF near the transmission cable? Does the electric company have ways to detect this or have counter-measures set up? How big would the wire need to be and made of what material? I am very interested in how all of...

Ok, the question says: "Find the magnitudes and directions of the current through the 22 ohm and 15 ohm resistors (the internal resistance of the batteries is negligible)" My question is how do i determine this if there's a second emf in the problem? here's a picture of the problem...

In physics class today, we did a project that I don't quite understand. We layed a small 50-turn coil flat on the table and held a magnet in a vertical position near the coil. We had the Galvanometer hooked up to make a clockwise current. The class then moved the magnet close to the coil and...

Consider a circuit comprised of a U-shaped perfectly conducting rail. In the circuit there is a voltage source, V, a resistor, R, and a switch. A perfectly conducting rod of mass, m, is free to slide on the U-shaped rail. Imagine the top end of the U facing open to the right, with the rod...

A 5.56m long steel beam is accidentally dropped by a construction crane from a height of 3.97m. The horizontal component of the Earth's magnetic field over the region is 28.4e-6T. Acceleration of gravity is 9.8 m/s^2. What is the induced emf in the beam just before impact with the Earth...

Please tell me if this is right: A coil contains 100 turns of wire in a loop 15cm in diameter. The loop is placed between the poles of a large electromagnet B= 1.0 T, with the plane of the loop perpendicular to the field. If the magnetic field is steadily reduced from 1.0 T to 0 in 16...

hello all!:smile: I have a question about electromagnetism. The question is "Can the back emf ever be greater than the battery emf in RL circuit?" can someone explain this one for me please?

I have a variation of the Motional EMF in Tiplers Physics Second Edition 28-1. A conducting rod of mass m and length l sliding along conducting rails connected by a resistor with a uniform magnetic field normal to the movement of the rod. The variation is that instead of just a resistor, the...

If you move a straight wire down through a magnet field, an emf is induced in the wire. If you then stop moving the wire, does the emf remain or does it disappear i.e do the electrons flow back? What about if you moved the wire out of the field?

Hey guys my teacher asked us to define back EMF in a motor, I am having a bit of touble understanding all of this can anyone explain it a little. Thanks

Ok, so here's the problem: Induced EMF A 5.80 cm diameter wire coil is initially oriented so that its plane is perpendicular to a magnetic field of 0.770 T pointing up. During the course of 0.140 s, the field is changed to one of 0.240 T pointing down. What is the average induced emf in the...

Okay here is the question: a) what is the internal resistance of a voltage source if its terminal voltage drops by 2 V when the current supplied increases by 5 A. b) Can the emf of the voltage source be found with the information supplied? I know that E = V - Ir, and I am pretty sure...

An infinitely long thin wire carrying a constant I is located along 0z-axis while a rectangular loop of dimensions axb located in the plane 0yz moves parallel to the 0y-axis with a constant velocity v. Assuming the two of the edges of the loop are parallel to 0z, compute the emf's induced on...

A square conducting loop with sides a lies on a table a distance s from a very long straight wire carryinga current I. a) Derive an expression for the magnetic flux through the loop. b) Derive an expression for the EMF induced in the loop if it is pulled away in a direction orthogonal to...

One more problem that's causing me grief: A square loop of wire, b meters on a side, moves with constant velocity v (m/sec) toward the right in the plane of a long straight wire carrying a steady current I amperes. Calculate the emf induced in the loop when the side of the loop nearest the...

ok, i guess i didnt see this forum ... i posted in another forum my question: https://www.physicsforums.com/showthread.php?s=&threadid=7593 ok, I am taking engineering physics II ... unfortunately, I am forced to take this as part of my COMPUTER SCIENCE degree ... (why i have no...