Solenoid Definition and 705 Threads

Hi. I have a solenoid, of length l, radius r, which has n turns of copper wire wound on it, carries a current of I amperes, and has a ferromagnetic core of relative permeability μr. How do I determine the magnetic field at a point in free space, x meters from the center of the solenoid? Also...

Consider an ideal solenoid (no resistance, no leakage reactance etc.) connected across an AC supply. The back EMF induced in it will be exactly equal and in opposite direction to the source voltage (which means that when a certain terminal of the AC supply is positive, the side of solenoid...

1. Assuming that both the windings of a transformer is wrapped around an iron core, how is an EMF induced in the secondary winding - isn't it necessary for flux to cut through the winding in order to induce an EMF? The flux cutting through the winding would apparently be very low..as most of it...

Homework Statement An aluminum ring of radius 5.00 cm and resistance 3.00 × 10–4 Ω is placed on top of a long air-core solenoid with 1 000 turns per meter and radius 3.00 cm. Over the area of the end of the solenoid, assume that the axial component of the field produced by the solenoid is half...

I have come across this problem, who to determine the direction of induced current. It keeps me wondering why the answer that i got is Fleming's right hand rule? Aren't it should be Right hand grip rule? Cz the usual and conventional way of inducing electricity in a solenoid is to pass the...

Hi- I'm trying to build a simple linear motion control using a solenoid. I've replaced the typical steel core for a permanent magnet core so that I can both push the armature out and pull it back in by flipping polarity (and without using any springs). This works nicely. Unfortunately, it still...

Hi, First post, and this stuff is way above my head so i am hoping some one can help me. So what I am after, i am after building a solenoid to to open a valve, this valve is holding back around 3000psi compressed air. its from a pressure washer gun. and takes quiet abit of force to open...

So I was reading a thread on PF talking about the radius of a solenoid and Bob S answered with a link: On that site, it states that the Radius = the outer radius - the inner. It doesn't make sense. What happens when there is only one layer of coil and the outer radius (OR) is basically the...

Homework Statement A solenoid with a large number of turns of wire is connected in series with an ammeter and a battery. An iron rod is moved towards the solenoid at constant speed. What will happen to the reading on the ammeter (A) as the rod moves closer to the solenoid, before...

http://img42.imageshack.us/img42/6336/14vu.png please explain your answer! also if u know of similar problems or where this problem is taken from do tell me coz i have an admission exam coming up soon please explain the following: 1. what is the flux like? 3. how the coil spins? z. how is...

I'm a Physics student currently working on some research with my advisor. My advisor doesn't know much about modeling solenoids so I've been tasked with reaching outside for help. I did that, but I can't remember the formula or the guy's name so I'm turning to you guys for help. There is some...

I'm a bit confused with the equation for a long solenoid. The usual derivation has us consider a rectangular loop enclosing N number of currents over the length L through it. So by Ampere's law one gets B=μNI/L. The currents and the loop look like this right? --------- | . . . . |...

Homework Statement A solenoid that is 117 cm long has a cross-sectional area of 20.0 cm2. There are 1010 turns of wire carrying a current of 9.56 A. (a) Calculate the energy density of the magnetic field inside the solenoid. (b) Find the total energy in joules stored in the magnetic field...

Homework Statement A long solenoid of radius R, length L (which is much longer than R), number of windings N, has a current I that is changing in time at a rate (dI/dt). What is the magnitude of the electric eld a distance R=2 from the axis of the solenoid? Homework Equations...

Homework Statement When putting a magnet into a solenoid, under what conditions is a current generated? The Attempt at a Solution In order for a current to be generated, the magnet needed to be moving as it passed through the solenoid. This is due to Faraday’s law, which states that an...

Hi, I've seen a couple of posts in the Homework section of Physics Forums about the fields of solenoids, but neither of them seem to address the problem that I have about it. The set-up is a long solenoid that has a sinusoidally varying current going through it. We can establish that the...

What would be the best method to model a solenoid? I tried writing a program that calculated the off axis elements of the solenoid but the value came out wrong. Any idea?

I have a question about solenoids. The formula for the magnetic field energy density is: \frac{1}{2}\frac{B^{2}}{μ} If I have an air-filled core, then μ=μ0. If I have a steel core, then μ will be ~ 100μ0. This implies that an air-filled core solenoid stores more energy than a steel core...

Homework Statement The figure below shows a short coil which is coaxial with a very long solenoid (you may approximate it as infinite.) Coil: Has 120 turns of radius 1.8 cm and resistance 5.8 . It is not attached to anything. Solenoid: Has 22700 turns/m and a radius of 1.6 cm. It receives an...

Homework Statement Consider a solenoid with a time varying current and with a coil of wire placed around it. Suppose there is a soft iron rod inside the solenoid. My question is: What happens to the (induced) current in the coil of wire as a result? Homework Equations Faraday, magnetic...

Homework Statement https://www.dropbox.com/s/17hsoz0zdfoston/Screen%20shot%202013-05-10%20at%2012.37.44%20PM.png 1) A voltage is applied to a solenoid such that a current is flowing in the indicated direction. Inside the solenoid is a single wire loop that is oriented in the same...

Hi guys. This is for an engr project that I am involved in. I have everything else worked out but this got me stomped. I've been searching for a while and can't find something that fits my application. basically the solenoid is controlling a dual acting air pneumatic cylinder. the solenoid...

Hello! I understand that by increasing the number turns the magnetic field is strengthened. But would that "extra" turns demand more power input from the power source?

I understand that the magnetic field at points inside the solenoid is the vector sum of the B field due to each ring. How can the field inside be uniform then since if you consider just one loop in the solenoid the value of the B field is different at different points in that circle or loop.

Homework Statement Inside a very long, straight and hollow plastic tube (R << L) we have ionized liquid moving at a velocity v = 100 m/s. The net charge per unit volume is n = 106 electrons/m3. The radius of the tube is R = 10cm. Around the tube we have a solenoid, with n = 100 loops/m...

The B field at the center of a stack of N circular loops each carrying current I is B = mu0 * N * I / (2a) where a is the radius of the loop, derived using Biot-Savart law. The B field inside a solenoid is B = mu0 * N * I / l where l is the length of the solenoid, derived using Ampere's...

I wound 4 layers on a piece of 3/4 conduit. The wire is 20 gauge (.032) and the coil length is 7 inches. I put 5 amperes into the coil and a bolt that fits the conduit didn't move. It stuck to one side of the conduit but it didn't snap in as I expected. What do I do to make this solenoid work?

So I'm building a solenoid that needs to move a load of 5 ounces, 0.4 inches. I'm pretty sure my calculations for the force inside the coil on a iron pin are correct: F = (B^2 * A) / (2 * Uo). Where B is the flux density, A is cross sectional area of pin Uo is permeability of free space...

Hi guys, I'm looking for an equation and/or proof of the magnetic field produced inside a solenoid with a finite length (hence, it shouldn't just be "muNOT n I." For some reason I can't find a simple proof anywhere. I have no idea where to start. ampere's law obviously doesn't work, and that...

Homework Statement As a new electrical technician, you are designing a large solenoid to produce a uniform 0.170 T magnetic field near the center of the solenoid. You have enough wire for 4200 circular turns. This solenoid must have a length of 1.10 m and a diameter of 1.50 cm. What current...

Homework Statement A coil of wire with N turns is placed around the a long solenoid with n turns per unit length carrying a current I as shown below, A)If a current I flows through the solenoid, derive an expression for the magnetic flux through the coil and explain why the size and shape...

I know that the answer will not be a or c due to effects of gravity. But I can't decide between b and d. I chose b because of lenzs law. I thought that since the south pole enter first, there will be an increasing flux upwards, coil opposes this by inducing an magnetic flux downwards. When it...

Ended up figuring out how to solve this problem. I just was not expecting certain parts of the results which lead me to believe I did it wrong.Homework Statement Voltage of battery is 5V Resistors are 5 Ohms The solenoid has no internal resistance 1.Need to find V_2 before switch is opened...

Just need a question cleared up. If I had a coil wrapped around a core, and I was calculating the magnetic field of the solenoid using B = μnI where n = N/L, I is current and μ is the permeability of my material N being the number of turns in the coil, and L being the length of the...

If instead of a disc shaped end I have a conical end , would there be any change in the measured magnetic field strength at the end of the solenoid keeping current, core and number of turns per unit length constant ?

Hello, I found an approximation for this log function: log \Bigg(\frac{\Lambda}{\rho} + \sqrt{1 + \frac{\Lambda^2}{\rho^2}} \Bigg), where \Lambda \rightarrow \infty . The above is approximated to the following, -log \bigg(\frac{\rho}{\rho_o} \bigg) + log \bigg(\frac{2 \Lambda}{\rho_o}...

URGENT: solenoid and superconductor questions Sorry I cross posted this, but I realized that general physics was probably a better place for it... I have a few questions regarding the levitation of a piece of superconductor using the field from a solenoid. In other words, I want to calculate...

Homework Statement From this video: http://www.youtube.com/watch?feature=player_detailpage&v=mdZo_keUoEs#t=77s it shows that the steel rod will eventually stay in the middle of the solenoid. At first the magnetic field of the solenoid would look like...

I know the magnetic field inside the solenoid is μIn/L and outside is 0 (provided that the point is near the solenoid). But if we had a long solenoid and choose a point far from the solenoid (and perpendicular to it), would it behave like a wire? Would the magnetic field be μI/2πR?

Homework Statement We're given two solenoids with identical currents and turns per unit length. But the solenoids have different diameters. Would a metal BB experience a larger acceleration in the smaller diameter tube, assuming we use the same BB in both solenoids it accelerates along the...

When we calculate magnetic field of iron core solenoid, should we multiply "relative permeability" or "effective permeability"? I thought that we should use relative permeability, but wiki(http://en.wikipedia.org/wiki/Solenoid) says that we should use effective permeability. I'm so...

Homework Statement A long solenoid with 1000 turns per meter and radius 2cm carries an oscillating current given by (5A)\sin(100\pi t). What is the electric field induced at radius r=1cm from the axis of the solenoid? What is the direction of this electric field when the current is...

Hello I have been doing some thinking related to Ampere law and behaviour of magnetic field inside materials of different permeability. In the process, I came up with the following thought experiment: Try imagining a very long solenoid with steady current I. Turns of the solenoid are...

If you have a solenoid positioned along the z axis... ...how would one find the b-field at slight deviations of x and y? I have been googling for hours and can't find anything other than the fact that it is very difficult! Thanks guys!

Homework Statement Suppose we have a toroidal solenoid with square cross section and whose axis of symmetry lies along the z axis. Suppose a current I(t)=kt runs through the solenoid. Find the induced electric field at an arbitrary point on the z axis. Homework Equations \oint \vec E \cdot...

I have to measure the magnetic field created by a solenoid. My attempt would be using a commercial Axial Hall Probe, or a Hall Sensor with some electronics. It has got an active (sensing) area with a diameter <1 mm. My coil is 12 mm long and has an inner diameter of 9 mm-s. My problem is that...

Hi all, I'm building a tennis ball launcher for my dogs, and was successful in building a spring loaded one with a "whacker bar" that rotated on a pin. A wiper motor turned the bar until the bar got to the half way point around the pivot, then the spring would pull the bar, hit the ball, and...

Instead of the usual B = μ0NI for field inside solenoid... how should i go about finding the field let say... 10cm away from one end of the solenoid 1. directly at the z-axis 2. not directly at the z-axis this is assuming the solenoid has finite length, finite number of turns ,finite...

Homework Statement A metal ring of radius r = 24 cm surrounds a solenoid of radius R = 2 cm and 10000 turns. The magnetic field inside the solenoid changes from 5 T to 3 T in 0.1 s. Find the magnitude of the non-Coulomb electric field along the ring. Answer in units of V/m Homework...

In a Faraday flashlight, a magnet is shaken to and fro in a solenoid to induce an EMF and thus current. Something like this: http://express.howstuffworks.com/gif/autopsy-flashlight-tube.jpg If the solenoid were to cover the entire length of the interior, and thus the magnet is only moving...