Emf Definition and 902 Threads

Homework Statement What is the necessary area for a generator that produces an emf of ##\mathcal{E} = 150V## when it spins at a ratio of 60 revolutions per second, in a magnetic field of ##B = 0.5 T##? Homework Equations ##\oint_{c} E \cdot dl = \mathcal{E} = -\frac{d}{dt}\iint_{s} B \cdot dS...

Homework Statement Four identical cells each having emf E and internal resistance r are connected in series to form a loop abcd as shown in figure (picture 1). Find potential difference across ab and ac. 2. Homework Equations V=IR equations for combination of cells and resistances The...

Homework Statement I'm working through an example with motional EMF and I'm having trouble understanding the directions of vectors so that I can apply induction law. The magnetic circuit seems complex because the circuit is used to analyze other situations but the air gap 3, the coil 3 and the...

I wonder if there is a way to calculate induced EMF in closed loops around bar magnet, which is traveling with constant velocity v to the right as depicted?

Homework Statement I tried to understand the problem b) and c).[/B] Homework Equations Faraday's law: ∇xE = - ∂B/∂t emf ε = Bdv Force : F =ma, Lorenz's force F=q(vxB) ==> ma = IdB Power : power of battery = εI, mechanical power of the wire = Fv The Attempt at a Solution I think I solved...

Suppose I had cylindrically-symmetric rotating magnet surrounded by a plasma. I rotate it on its axis at a constant angular velocity, and so the electric field E produced is non-solenoidal and can be described as the negative gradient of some potential V(x,y,z). The electric field is induced...

1. A magnetic dipole antenna is used to detect an electromagnetic wave. The antenna is a coil of 50 turns with radius 5.0 cm. The EM wave has frequency 870 kHz, electric field amplitude 0.50 V/m, and magnetic field amplitude 1.7 X 10-9 T. (b) Assuming it is aligned correctly, what is the...

Homework Statement There is some current in the bottom coil. The question asks which would not be able to light the lightbulb - rotating the insulating handle 90 degrees - increasing resistance of variable resistor -reducing resistance of variable resistor - moving the insulating handle...

Homework Statement The EMF of the cell : Ni(s) | Ni2+ (0.1M) || Au 3+ (1.0M) | Au (s) is [ given E°(Ni2+/Ni)= -0.25V; E° (Au3+ / Au )= +1.50V ] Homework Equations E°cell=E°(cathode)-E°(anode) For SRP. Nernst equation The Attempt at a Solution SOP is given, therefore converting to SRP we...

Does light traveling through a fiber optic cable generate any sort of detectable electromagnetic field? Please forgive the stupid question. It’s something that popped into mind recently and google hasn’t adequately answered for me. I’m not a scientist or physicist. :blushing:

Can someone please help with this thought experiment? I have sought advice elsewhere but it remains unclear to me. I have a straight piece of two conductor "figure eight" wire (like speaker wire or US power cord) laid out left to right. I connect the output from a push-pull type audio...

Homework Statement translation ; we know the values of R1 = 1 ohm R2= 2 ohm R3= 6 ohm R4= 2 ohm R5= 4 ohm R6= 4 ohm we can also see the voltmeter reading a potential difference value of 8 volts , and the...

Let's say you have an open loop (like a section of a circle) in a changing magnetic field. I think there would be an induced EMF, but no current. What I can't figure out, though, is how to calculate the induced EMF. Using Faraday's law doesn't seem to help, as there's no enclosed area.

Homework Statement A current I(t)= (0,160 A s^{-3}) t^3 flows through an ideal solenoid with a turns density n = 9,00 \cdot 10^{-3} m^{-1} and a cross sectional area A_s=2,00\cdot 10^{-4} m^2 A single loop of wire has the same axis as the solenoid, but its radius is larger. That is: the loop...

I have a question in my book and it’s confusing me a bit. I tried to search online for similar solved problems but couldn’t succeed. So here it goes:Calculate the induced EMF in a conductor loop when the angle between \vec{A} ~ and~ \vec{B} ~is~ changed ~from ~{0 °}~ to ~{α °} in 1 second...

Homework Statement Homework EquationsThe Attempt at a Solution First I will label a few points . A is the point on the ring touching the rails , vertically below P . B is the point on the ring touching the rails , vertically below Q . T is the topmost point on the ring . M is the bottommost...

Homework Statement We have to measure emf of a battery. We have to voltmeters. Each of them when connected alone across the battery, they read V1 = 0.9V and V2 = 0.6V and when both of them are connected to the battery simultaneously, they both read V3 = 0.45V . What is the emf of...

Homework Statement In Solenoid, is emf E= N. d(phi)/dt, or is it simply d(phi)/dt? Some books contain the latter one. It was not a big deal until i gave a thought about it. Since increasing the N, we are actually increasing the value of n, thus increasing B= (mu) .n.I So, by placing N in front...

Homework Statement The correct answer is D Homework Equations The Attempt at a Solution The current is clockwise( in the first picture at least) due to right hand rule. The magnetic flux is changing, the direction of the induced emf depends on the direction of change (increase or...

Homework Statement Correct answer is Homework Equations emf = I(R + r) The Attempt at a Solution When current flows the voltage across the battery is less than the emf so it's not A I really don't understand why the answer is C because B, C, D all seem correct to me. Please help me with...

Homework Statement [/B] A battery has an emf of 9 V and an internal resistance of 2 Ω. If the potential difference across its terminals is greater than 9 V: A. it must be connected across a large external resistance B. it must be connected across a small external resistance C. the current must...

Homework Statement A motor as an internal resistance of 0.5 ohms. It draws 20 amperes at full load from a 120-V supply. a) What is the emf of the motor? b) What is the load resistance? Homework Equations Potential difference between the terminals = emf - Ir (r = internal resistance) (P.D...

Hi, I have a problem understanding the ac capacitive circuit, where Vc = Vm * sin(ωt), and, current leads the voltage, so at t = 0, v = 0 which means no emf, no pushing energy for the electrons, I think, then how current is max? what is the energy source that supplied the electrons with the...

I am attempting to make a basic model of an alternator and determine terminal voltage levels at several different current levels. The alternator design looks like this: 900 RPM fixed, 60hz, single phase 2000 gauss permanent magnet Flux Density, Magnet circumferential velocity 9.58 m/sec, 4...

I understand the direction compnent of this question. But I don't understand where the magnitude of the induced current came from? I'm assuming faradays law wasn't used as there wasn't a change in magnetic field?

Homework Statement [/B] A radio transmitter radiates isotropically at the frequency of 90.8 MHz. The peak magnetic field at a receiver, 9km from the transmitter, is ##9x10^{-10}T##. Calculate the maximum amplitude of the induced emf in a 12 turn coil with area A = ##90cm^{2}## at the receiver...

We know that primary of a transformer is a coil(mono or multilayer) from a conductive material, usually copper, which have a proper lattice.Inside the lattice is a cloud of free electrons .When in circuit, a voltage is applied at the coil heads. 1.When voltage is applied , do we have a...

Homework Statement Homework EquationsThe Attempt at a Solution Sorry for the unclear image . EMF induced in the left loop = 8 Total Resistance of the left loop = 6 Ohms Current will be induced in anticlockwise direction in the left loop of magnitude 4/3A. EMF induced in the right...

Homework Statement Homework EquationsThe Attempt at a Solution The current will decrease , as a result an EMF will be induced in the cylinder . The EMF induced E = -dΦ/dt I am assuming magnetic field through the cylinder to be same as that at the center of the a current carrying coil...

Homework Statement [/B] A conducting coil of radius R is outside a long solenoid with a cross section of radius r. What is the emf induced in the coil? Most example problems of this type I think are solved based on Faraday’s Law. These examples do not use the distance from the solenoid to the...

Let's say I feed the same electrical signal into the opposed windings of a contrawound toroidal coil, and that this results in their individual electromagnetic fields cancelling to "zero". Can someone explain what in turn happens to the virtual photons associated with those canceled fields? For...

Homework Statement A small but very powerful bar magnet falls from rest under gravity through the center of a horizontal ring of conducting wire, as shown in the figure below (on the left). The speed-versus-time graph, in arbitrary units, of the magnet will correspond most closely to which of...

In my experiment, I intended to find out how the change in the bar magnet drop height from solenoid affected the emf induced in the solenoid, however, I am unable to come up with an equation that shows a relationship between the two variables. I have thought of Biot-Savart law, but I do not...

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...

The context is an ac circuit with only one element - the inductor. My textbook says that the self-induced emf increases with increasing angular frequency, but I'm having trouble seeing this mathematically. If self-induced emf = ε = -L(dI/dt) and L = X/ω, then emf and ω are inversely related...

A friend mine of gave me a problem : Calculate the Emf b/w the axis and surface of a long current carrying wire of radius ##r## and current density ##J##. I am not able to understand why there would be a potential difference between the axis and surface but i think that either of these could...

Why do EMF meters measure ELF and VLF in flux density units but RF in power density units? Is it because ELF/VLF have low power density and high flux density, and RF has high power density and low flux density? They are all EM waves, right? what's driving the difference in measurement units? thanks

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...

1. The problem statement I did a laboratory work in which I had to find power and internal resistance. I used an ordinary battery so it's closed circuit. I did all tasks except writing a hypothesis and conclusion I can't really think of it. I don't know what to write since I just measure using...

Homework Statement Homework EquationsThe Attempt at a Solution First part is easy . Area of the triangular loop is A = (1/2)(2R)(R) = R2 Induced EMF in loop ABC = Rate of change of flux = dΦ/dt = AdB/dt = R2(dB/dt) which is correct . Now the second part has stumped me . I would really...

Homework Statement I keep telling myself that this problem should be easy, but I keep getting the wrong answer. Any help is appreciated. A generator has an armature with 500 turns, which cut a flux of 8.00 mWb during each rotation. Compute the back emf it develops when it runs as a motor at...

I'm having a difficult time understanding why the internal resistance of the EMF source is disregarded in this problem. 1. Homework Statement You are asked to determine the resistance per meter of a long piece of wire. You have a battery, a voltmeter, and an ammeter. You put the leads from the...

Homework Statement I am attempting to solve the circuit for three currents (I1, I2, I3). I am starting with I1 in terms of I2, then using a third equation to solve for I2 in terms of E and R. I wrote my loops at the bottom of the page. I am using Loop 1 @ B, Loop 2 @ B, and Junction at B to...

Homework Statement Modification: Take two big loops kept on both sides of the small loop at a distance a from the corresponding end of the small loop. Homework EquationsThe Attempt at a Solution The flux through the bigger loop is equal to the flux through the smaller loop, provided that the...

Homework Statement Homework EquationsThe Attempt at a Solution Assuming the current is steady, I = JA, where J is the current density and A is the cross- sectional area ##E = J/\sigma## Can I take ##\sigma ## uniform here ?

Homework Statement A current of 10A is switched off at time t = 0 in a long cable (picture in attachments). It powers a device, with the current return wire having 5 mm separation. A wire loop of dimension 5 by 5 cm is located at a distance 3 cm from the cable. 1) What Emf is induced in the...

Homework Statement (ignore the suggested problems for test 3.) If for whatever reason the image doesn't load the given's are that: The area is 25pi(.125m)^2 (A circular coil with 25 turns and a radius of 12.5cm.) The magnetic field varies with time and is...

HelloLast week I was confronted with a situation where an industrial equipment, with a large equipotential mass (metal casing) that was not grounded, had a ground tension, measured with Fluke, of 382 vac. I put a 220 Vac bulb and nothing happens, the bulb remains off and is not burned out. By...

Homework Statement A battery of emf 2V and internal resistance 0.1ohm is being charged with a current of 5 ampere. In what direction will the current flow inside the battery?What is the potential difference between the two terminals of the battery? Homework Equations If a battery of emf E and...

Homework Statement [/B] Homework EquationsThe Attempt at a Solution Solution for Q1: Solution for Q2: Solution for Q3: Are they correct?