# Relationship between magnetic field and induced current flows

From now on we'll investigate the inter-connection between the two, starting a voltage by changing the magnetic field that passes through a coil of wire. Not only can a moving magnet cause a current to flow in the coil, the. What Lenz's Law tells us is that the direction of the induced current in the loop is like the magnetic field times the cross-sectional area that it "goes through" This increasing/decreasing difference is why the induced current. Faraday's law of induction makes use of the magnetic flux law which states that an induced current will flow in the to exploit flux linkage by creating a tightly wound coil of.

This would be consistent with the effect of a repulsive force from the two opposing magnetic fields.

## Induced current in a wire

Interestingly, this effect can occur in any conductor moving through a magnetic field. This effect has many applications in engineering where it is known as eddy-current braking and employed on trains and amusement park rides.

Induction in parallel wires If a pair of wires are set parallel to one another it is possible for a changing current in one of the wires to induce an EMF pulse in the neighboring wire.

This can be a problem when the current flowing in neighboring wires represents digital data.

Ultimately this effect can limit the rate at which data can be reliably sent in this manner. Figure 5 shows a pair of parallel wires.

## Induced Current

One is connected to a battery via a switch and current meter while its neighbor forms a loop with just a current meter in series. Suppose the switch is briefly switched on then off. Qualitatively speaking, what will happen to the current measured in the neighbor? Current pulses due to induction between parallel wires.

### magnetic fields - How to determine the direction of induced current flow? - Physics Stack Exchange

Solution When the switch is closed current begins to flow down through the left wire. What you can conclude from all these observations is that a changing magnetic field will produce a voltage in a coil, causing a current to flow. To be completely accurate, if the magnetic flux through a coil is changed, a voltage will be produced. This voltage is known as the induced emf. The magnetic flux is a measure of the number of magnetic field lines passing through an area.

If a loop of wire with an area A is in a magnetic field B, the magnetic flux is given by: If the flux changes, an emf will be induced. There are therefore three ways an emf can be induced in a loop: Change the magnetic field Change the area of the loop Change the angle between the field and the loop Faraday's law of induction We'll move from the qualitative investigation of induced emf to the quantitative picture.

### Induced current in a wire (video) | Khan Academy

As we have learned, an emf can be induced in a coil if the magnetic flux through the coil is changed. It also makes a difference how fast the change is; a quick change induces more emf than a gradual change.

This is summarized in Faraday's law of induction. The induced emf in a coil of N loops produced by a change in flux in a certain time interval is given by: Recalling that the flux through a loop of area A is given by Faraday's law can be written: The negative sign in Faraday's law comes from the fact that the emf induced in the coil acts to oppose any change in the magnetic flux.

This is summarized in Lenz's law. The induced emf generates a current that sets up a magnetic field which acts to oppose the change in magnetic flux. Another way of stating Lenz's law is to say that coils and loops like to maintain the status quo i. If a coil has zero magnetic flux, when a magnet is brought close then, while the flux is changing, the coil will set up its own magnetic field that points opposite to the field from the magnet.

On the other hand, a coil with a particular flux from an external magnetic field will set up its own magnetic field in an attempt to maintain the flux at a constant level if the external field and therefore flux is changed.

The coil is 20 cm on each side, and has a magnetic field of 0. The plane of the coil is perpendicular to the magnetic field: There is only an induced emf when the magnetic flux changes, and while the change is taking place.

If nothing changes, the induced emf is zero. While the change is taking place, what is the induced emf in the coil?

This same "reverse" rule can also be phrased as Lenz's law. This says that induction works like inertia: As you may know, a wire also produces a magnetic field.

The direction of this magnetic field looks like this: If you combine your hands together, pointing your left thumb up to indicate an upward change of magnetic field, then putting your right thumb against your left index finger, you'll see that your right fingers curl into your palm, opposite your left thumb.

Lenz's law gives some awesome quick intuitions.