Ground, Neutral And Hot Wires (US/Can) - The Engineering Mindset

à 27 avril

Learn about what happens to a current-carrying wire in a magnetic field in this cool electromagnetism experiment!The wires attract with each other. (b) Figure shows the magnetic field for two straight parallel wires carrying current in opposite directions. A thick copper wire is used so that a larger current will flow to produce a stronger magnetic field. The d.c. power supply should be switched off after making the...Wires come in many forms and are made from many materials. They may seem simple but engineers are aware of two important points: -Electricity in long wires used in transmission behaves very differently than in short wires used in design of devices...A long straight wire of a circular cross-section (radius a) carrying steady current I. The current I is uniformly distributed across this cross-section. Calculate the magnetic field in the region r<a and r>a where a is the distance at which the magnetic field is calculated.Magnetic fields around a wire carrying an electric current. Solenoids. A solenoid is a long coil of wire. When a direct electric current is passed through it, the shape of the magnetic field is very similar to the field of a bar magnet. The field inside a solenoid is strong and uniform.

How does a current carrying conductor produces... - A Plus Topper

Within a wire carrying direct current, electrons hop from atom to atom while moving in a single direction. Thus, a given electron that starts its trek When a conductor (such as a wire) moves through a magnetic field, the magnetic field induces a current in the wire. But if the conductor is stationary...If both wires carry a current how far apart must their parallel sections be so that the net magnetic field at P is zero? 34. The infinite, straight wire shown in the accompanying figure carries a current The rectangular loop, whose long sides are parallel to the wire, carries a current What are the...A long straight wire carrying a current has a magnetic field due to moving charges which will depend on the right-hand rule. 1) A wire of 30 cm length carries a current I= 2 A. what is the magnetic field at 50 cm from the wire? Answer: From the formula of the magnetic field of the straight we substitute...Assuming that my understanding of how a wire carries DC current is correct, I would like to understand how a wire carries alternating current. Especially if the length of the wire was large, say 3 * 10^8 meters, then would the movement of electrons on one end of the wire be "in sync" with the...

Wires and Cables

Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the magnetic force that each wire exerts on the other? It stays the same.where R = Resistance, ρ = constant called Resistivity, L = Length and A = Area, From the formula, above, the Resistance R would decrease if the length is small. So from the options, that correspond to: shorter wires.When we place a wire which carries the electric current in the magnetic field, each of moving electrons (which comprise the current) will experience the Lorentz Force. It means that this wire will start moving if there is no other strong enough force which can stop it, for example a friction force.In the wiring of a building, the wires carrying the current in and out are different and never touch directly. The charge passing through the circuit always passes through an appliance (which acts as a resistor) or through another resistor, which limits the amount of current that can flow through a circuit.Magnetic force on current-carrying conductors is used to convert electric energy to work. (Motors are a prime example—they employ loops of wire and are considered in the next section.) Magnetohydrodynamics (MHD) is the technical name given to a clever application where magnetic...

There are several problems with this question.

Firstly, the Tesla (T) is a unit of magnetic flux density (B), not of magnetic field strength (H). The unit of field strength is Amps/m (A/m). It is important in all scientific studies to be absolutely clear about the distinctions between the various quantities being discussed, their units, and symbols.

Secondly, we are not told enough about the disposition of the current-carrying wire to be able to estimate properly the flux density in the space around it. If, for the sake of simplicity we take the impractical case of a wire which is is straight and infinite in extent we can use the formula -

B = u*I/(2*pi*r)

Where u is the permeability of air (taken to be the same as that of vacuum) r is the distance from the wire, I is the current. Clearly this will only relate approximately to a practical experiment of the kind that Oersted did. An alternative (more practical) assumption would be that the wire is in the form of a circular loop. But then we would need to know a lot more extra information, including the size of the loop, the exact position of the compass relative to the loop and the orientation of the plane of the loop relative to the earth's magnetic field direction.

A further point is that B is a vector quantity, and its effect on a compass needle depends on the direction of the component of B created by the wire in relation to the component of B due to the earth's magnetism. If these two components happen to be in the same direction, the needle would not be deflected at all however large the current might be. To pretend that a value of B of 1.25T is adequate to move the needle without regard to the direction of B is completely false and gives the student a very poor idea of what is involved when dealing with vector quantities.

So this is a very poor question. To answer it, I shall treat it as though it were asking -' what current is required to create a component of flux density of magnitude 1.25*10^-5T at a distance of 0.32m from an infinite straight wire'.

Using B = u*I/(2*pi*r) ....

I = 2*pi*r*B/u = 2*pi*0.32*1.25*10^-5/1.25*10^-6 = 20A

Look here for a discussion of B near a long straight wire -

http://hermes.eee.nott.ac.uk/teaching/cal/h51emf/e...

Hope this helps...

I cannot help feeling that your teacher is not helping you very much by confusing the concepts of field and flux density on the one hand, and by being uncritical about the application of simple idealised assumptions to practical cases, on the other, and in particular by glossing over the question of vector addition. None of this will help you to understand electromagnetism.