CH. 25 Electricity And Magnetism

moving charge is caused, or induced, by the relative motion between a wire and a magnetic field can also be caused by changing a current in a nearby loop.

inducing voltage by changing the magnetic field in loops of wire The creation of voltage when a magnetic field changes with time. If the magnetic field within a closed loop changes in any way, a voltage is induced in the loop.

The induced voltage in a coil is proportional to the product of it's numbers of loops, the cross-sectional area of each loop, and the rate at which the magnetic field changes within those loops. The greater the number of loops of wire that move in a magnetic field, the greater the induced voltage. When a magnet is plunged into a coil that has twice as many loops as another coil, twice as much voltage is induced. It is more difficult to push the magnet into a coil that has more loops because the magnetic field of each current loop resists the motion of the magnet. Loops produce magnetic field that is opposite of inserting magnet, thats why theres a resistance.

No. EMI is not a source of energy but a method of transforming mechanical energy into electric energy. Work must be done to produce energy by EMI.

If the loop is an electric conductor then current is induced

Ex: we can plunge a magnet in and out of a closed loop of rubber and in and out of a closed loop of copper. The voltage induced in each is the same, provided that the loops are the same size and the magnet moves with the same speed. But the current in each is quite different. Electrons in the rubber sense the same electric field as those in the copper, but their bonding to the fixed atoms prevents the movement of charge that so freely occurs in copper.

The changing magnetic field in the coil induces voltage. In this way, information stored magnetically on the disk is converted to electrical signals.

More work is required to provide more energy to be dissipated by more current in the resistor. You can also look at it this way: when you push a magnet into a coil, you cause the coil to become a magnet (an electromagnet). The more loops there are in the coil, the stronger the electromagnet that you produce and the stronger it pushes back against the magnet you are moving. If the coils electromagnet attracted your magnet instead of repelling it, energy would be created from nothing and the law of energy conservation would be violated.

As the magnetic field strength inside the coil is increased (as the magnet enters the coil), the induced voltage in the coil is directed one way. When the magnetic field strength diminishes (as the magnet leaves the coil), the voltage is induced in the opposite direction. The frequency of the alternating voltage that is induced equals the frequency of the changing magnetic field within the loop.

An electromagnetic induction device that produces electric current by rotating a coil within a stationary magnetic field. A generator converts mechanical energy into electrical energy.

In a motor, electric energy is the input and mechanical energy is the output; in a generator, mechanical energy is the input and electric energy is the output. Both devices simply transform energy from one form into another.

When charge moves along the wire, there is a perpendicular upward force on the charge. since there is no conducting path upward, the force on the charge tugs the wire upward.

When a wire with no initial current is moved downward, the charge in the wire experiences a deflecting force perpendicular to its motion. there is a conducting path in this direction so the charge moves, constituting a current.

Always.

- a voltage is induced in the wire - a current in created in the loop of wire - electromagnetic induction occurs

the changing magnetic field that produces it alternates

change in magnetic field for operation

power line, and the secondary senses the magnetic field and creates voltage.

when it breaks, it charges up the battery, and you don't break nearly as much on the highway as you do during city driving.

You need something to magnetize, and nylon strings cannot be magnetized, but steel strings can.

high voltage --> low voltage. The potential difference when the long bushy tail of a squirrel touches more than one wire is what ends up killing the squirrel. long wires = more resistance = loss due to heat.

They both, independently, discovered electromagnetic induction

the induced voltage in a coil is proportional to the product of its number of loops, the cross sectional area of each loo and the rate at which the magnetic field changes within those loops

both frequencies are the same

the current is ac because the induced voltage is ac

Faraday and Henry made the discovery, Tesla put it to practical use

steam commonly supplies energy to a turbine

an MHD generator has no moving parts

power is the rate at which energy is transferred

a transformer changes voltage and current but not energy and power

a step down transformer steps down voltage

a transformers operation depends on change - hence alternating current, or ac

yes, this is called self induction

no wires are needed. personal electronic devices attest to this.

Electromagnetic induction requires change - of the intensity of a magnetic field, or of motion in a magnetic field

the magnetic domains that become aligned in the iron core contribute to the overall magnetic field of the coil and therefore increase its magnetic induction.

work must be done to move a current-carrying conductor in a magnetic field. this is true whether the current is externally produced or produced as a result of the induction that accompanies the motion of the wire in the field. its also a matter of energy conservation. there has to be more energy input if there is more energy output.

in accord with electromagnetic induction, if the magnetic field alternates in the hold of the ring, an alternating voltage is induced in the ring. because the ring is metal, its relatively low resistance results in correspondingly high alternating current.

agree. light is electromagnetic radiation that has a frequency that matches the freq to which our eyes are sensitive.