23.2 Faraday's Law of Induction: Lenz's Law

23.2 Faraday's Law of Induction: Lenz's Law

• The magnetic field and the area over which it exists are related to magnetic flux.
• The emf is related to the flux.

• The examples given so far are the result of a change in magnetic flux.
• The angle is changed when the generator is rotating.
• The change in and how quickly the change is made affect how great an emf is.

• The emf depends on a few factors, according to Faraday's experiments.
• The emf is proportional to the change.

• If a coil has turns, an emf will be produced that is times greater than for a single coil.

• The units for emf are the same as always.

• The minus sign is very important.
• The minus means that the emf creates a current I and magnetic field B that is opposed to the change in flux.
• Faraday was aware of the direction, but he was not credited for discovering it.

• There is a field in the opposite direction of the bar magnet's created by the current in the coil.
• Induction is one aspect of the law.
• The current direction shown is consistent with RHR-2 and the direction shown is opposed to the change in flux.

• A sketch of the situation can be used to record directions.

• Determine the direction of the magnetic field.

• Determine if the flux is increasing or decreasing.

• Determine the direction of the magnetic field.
• Adding or subtracting from the original field is opposed to the change in flux.

• RHR-2 can be used to determine the direction of the current that is responsible for the magnetic field B.

• The direction of the emf will now drive a current in this direction and can be represented as current emerging from the positive terminal of the emf and returning to its negative terminal.

• In this chapter, we will look at some of the applications of the law.
• There are several things that have to do with data storage and magnetic fields.
• There is an important application for audio and video recording tapes.
• A plastic tape moves past a recording head.
• A coil of wire is wrapped around a ring of iron in the recording head.
• A varying input current from a microphone or camera goes to the recording head.
• The signals that produce the magnetic fields at the recording head are a function of the signal amplitude and Frequency.
• The magnetic field orientations of the iron oxide molecule on the tape are changed as the tape moves past the recording head.
• The structure of the recording head is similar to that of the magnetized tape.
• The different magnetic field orientations of the iron oxide molecule on the tape cause an emf in the coil of wire.
• A loudspeaker or video player will receive this signal.

• Magnetic tapes are used to record and play back audio and video.
• There are recordings on a spinning disk.

• The heads were made to work on the principle of induction.
• A series of 0's or 1's are written on the spinning hard drive as the input information is carried in digital rather than analog form.
• Most hard drive readout devices don't work on the principle of induction, but use a technique known as giant magnetoresistance.
• The magnetic stripe on the back of your credit card can be used at the grocery store or the ATM machine.
• This works the same way as the audio or video tape mentioned in the last paragraph in which a head reads personal information from your card.

• When electrical signals need to be transmitted across a barrier, it's an application of Electromagnetic Insturment.
• Consider the implant.
• Sound is picked up by a microphone on the outside of the skull and used to create a magnetic field.
• A current is transmitted from the bone beneath the skin to the inner ear through a receiver.
• There are instances where electric signals need to be conveyed across various media.

• The electric current is transmitted across the medium.
• The device on the baby's head causes an electrical current to travel through the bone beneath the skin.

• Transcranial magnetic simulation is a contemporary area of research that is being successfully implemented.
• Depression and hallucinations can be traced to irregular electrical activity in the brain.
• In transcranial magnetic stimulation, a magnetic field is placed close to certain areas of the brain.
• Weak electric currents can result in the recovery of electrical functioning in the brain tissue.

• It may be a cause of sudden infant deaths if you have sleep apnea.
• Breath can stop frequently during sleep.
• It is very dangerous to stop for more than 20 seconds.
• It is possible for a person with sleep apnea to have strokes, heart failure, and tiredness.
• The stopping of breath is a concern for infants.
• One type of monitor is used to alert parents when a child is not breathing.
• An alternating current runs through a wire wrapped around an infant's chest.
• The expansion and contraction of the infant's chest changes the area through the coil.
• A pickup coil located nearby has an alternating current that is caused by the changing magnetic field of the initial wire.
• A parent can be notified if the child stops breathing.

• The law is related to the use of energy.
• A change in energy means a change in emf.
• There is energy that can enter or leave.
• It is a consequence of Lenz's law.
• The law says that as the change begins, it slows the change.

• Since it was changed from 0.0500 to 0.250 T, the area of the loop is.

• This is not large enough for most practical applications.
• There are more loops in the coil, a stronger magnet, and faster movement that make it a practical source of voltages.

• Use a bar magnet and coils to learn about the law.
• You can make a light bulb glow by moving a bar magnet.

• The direction and magnitude of the current is shown by a meter.
• To see the direction and magnitude of the current, use a meter or view the magnetic field lines.