# induced emf

1. ### How to find the charge at time = t (at any instant)

I was not able to derive the charge on the capacitor. But then, I arbitrarily assumed $\phi=B.A$ (Dot product of Magnetic field and Area) Then, proceeding as follows, $\phi=BA\cos(\omega_0 t)$ $\frac{d\phi}{dt}=−BA\omega_0\sin(\omega_0 t)$ Now at $t=0, \phi=BA\cos(0)=BA$ Therefore...
2. ### EMF induced in a rotating rod having mass

I first calculated induced emf and then calculated torque about O.But what will i do further.I think i need to find current and then fidn emf=IR. Help please.
3. ### Finding the induced EMF in a solenoid-wire system

I know that $B = \mu n I$ and $\phi = B \pi R^2$. So with have $d\phi / dt = \mu n \alpha \pi R^2$. But I don't know what to do with this? is this the answer? I don't think so but I don't know what to do after this.
4. ### B EMF and Faraday's Law

1) Take a non-steady circuit such as an LR circuit. Why does Kirchoff's voltage law work when analyzing such a circuit? Is it because we're assuming that dI/dt and thus dB/dt are approximately zero thus meaning that curl E is approximately zero? 2) ε, the electromotive force, is the line...
5. ### Current induced on a coil by a changing magnetic flux in another coil

I will first calculate the magnetic flux of the coil in motion. $$\frac {d\phi}{dt} = -\frac {dB_{loop}}{dt}A = -\frac{d}{dt}(\frac{\mu_o}{4\pi}\frac {2\pi NR^2I}{(R^2+z^2)^{\frac{3}{2}}})A$$differentiating in terms of $z$, we get \frac {d\phi}{dt} =(\frac{\mu_o}{4\pi}\frac {6\pi^2...
6. ### Induced EMF in closed loops around bar magnet

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?
7. ### Find the maximum amplitude of the induced EMF

1. Homework Statement 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...
8. ### B Flux through a Coil

Thank you for reading my post. I can understand why a change in magnetic flux through a conducting surface would induce an emf, but how does this work when inducing an emf through a coil? How does the flux through the empty space between the wires have an effect on the electrons in the wire...
9. ### B Flux in a Uniform Magnetic Field

Thank you for reading my post. I was thinking about induced emf and magnetic flux and I realized I have a huge misunderstanding, but I don't know exactly what it is. Below I will list 4 statements which I logically know cannot all be simultaneously true. Can you please tell me which one(s) are...
10. ### Induced Voltage of Rotating Circular Loop

HI! I'm a student, this question appeared in one of the old tests. I though I had it solved but apparently I must have missed somewhere. Could someone please at least hint me where I went wrong? 1. Homework Statement Thin wire is wound into circular frame with radius $r = 0.05m$ which...
11. ### I Induced EMF in a half vs. whole ferrite toroid

Hello all - I've stumbled upon what seems to be a pretty basic magnetic materials question that's got me stumped. Maybe one of you can help me figure this out. I did the following experiment (see figure below): Put a ferrite toroid around a current carrying wire carrying 12 Amps RMS at 120V...
12. ### Induced EMF from moving conducting rod

1. Homework Statement Lets say we have two horizontal rails connected by a resistor to the left, and we have a movable conducting rod that slides without friction on the rails.There is a uniform magnetic field going into the page. 2. Homework Equations F = ILB 3. The Attempt at a Solution...
13. ### Zero induced EMF

1. Homework Statement Question I need help with: If wire AB of problem 9 moves with a velocity of 50.0 m/s to the right, at what rate should B change when the wire is at a distance of 5.00 cm from the left end of the loop, such that there will be no induced emf in the circuit? Answer: 300 T/s...
14. ### AC frequency vs induced EMF

If you have a one solenoid inside another (with the same number of coils of wire) the current is going through the inner one. How does the induced EMF in the outer one depend on the frequency of AC in the inner one
15. ### Calculating multiple magnitudes for induced electric field

Let's say I place two different size conducting loops inside of a uniform magnetic field. For the sake of the diagram I have the loops share a point, but just treat them as though they are not touching. Then I decrease the value of the magnetic field very quickly. \frac{dB}{dt} =...
16. ### MRI Electromagnet Interference in a Figure-8 cable

The prevailing wisdom is that coiling excess signal cable under an MRI magnet for storage in a figure-8 configuration will reduce or eliminate induced noise onto the cable from the pulsing fields from gradient coils. I am starting to doubt this, however. A quick diagram of a figure-8 looped...
17. ### The physics behind an electric motor and induced emf?

I am having trouble understanding a process in the electric motor. using this website as a frame of reference (http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/mothow.html), as an electric current is passed into that magnetic field, shouldn't the current also be creating a magnetic field, and...
18. ### Induced emf of Sliding Wire Down Rails

1. Homework Statement [This is the best image I could find] The link on the bottom part of the rails is now removed creating two parallel wires that are not connected (so no longer U shaped but just two rails). Now a wire of length L, mass m and resistance R slides without friction down...
19. ### Induced EMF, bar moving through magnetic field

1. Homework Statement A long, straight wire as shown below carries a constant current I. A metal bar with length L is moving at a constant velocity V as shown. Point ‘a’ is a distance ‘d’ from the wire. a) Derive an expression for the EMF induced in the bar. b) Which point ‘a’ or ‘b’ is at a...
20. ### Would a wire's magnetic field increase the net-B field?

From the following diagram: When a wire is placed in a magnetic field $B$, and current starts to flow within that wire. It creates it's own magnetic field($B_w$). Will $B_w$ interact with the external field $B$? If it does, is the result of the interaction the Lorentz force? Also...