ch37_jdmk

Chapter 37-Electromagnetic Induction 37-1 Electromagnetic Induction 37-2 Faraday’s Law  37-3 Generators and Alternating current · If one end of a magnet is plunged in and out of a coil of wire, the induced voltage alternates in direction. · When the magnetic field strength inside the coil is increased, the induced voltage in the coil is directed one way and when the magnetic field strength diminishes, the voltage is induced in the opposite direction. · A generator is a device that continuously rotates a coul of wire inside a magnetic field by faraday’s law as the amount the magnetic field passing through the coil. · A generator is the opposite of a motor because a motor converts electric energy to mechanical energy and a generator converts mechanical energy to electric energy. 37-4 Motor and Generator Comparison 37-5 Transformers 37-6 Power Transmission 37-7 Induction of Electric and Magnetic Fields 37-8 Electromagnetic Waves
 * Electric current could be produced in a wire by simply moving a magnet in or out of a wire coil.
 * Voltage was induced by the relative motion between a wire and a magnetic field.
 * The production of voltage depends only on the relative motion between the conductor and the magnetic field.
 * Voltage is induced whether the magnetic field of a magnet moves through a stationary conductor, or the conductor moves through a stationary magnetic field.
 * The amount of voltage induced depends on how quickly the magnetic field lines are traversed by the wire. This therefore means that very slow motion produces hardly any voltage at all and quick motion induces a greater voltage.
 * The greater the number of loops of wire that move in a magnetic field, the greater the induced voltage and the greater the current in the wire.
 * For example, pushing a magnet into twice as many loops will induce twice as much voltage and pushing it into ten times as many loops will induce ten times as much voltage.
 * When there are more loops, you cause more current to flow in a coil, and this makes the coul act as a more powerful electromagnet.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">A coil with more loops is a stronger magnet and pushes back harder.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The amount of voltage induced depends on how quickly the magnetic field changes. Very slow movement of the magnet into the coil produces hardly any voltage at all. Quick motion induces a greater voltage.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Electromagnetic induction-inducting voltage by changing the magnetic field around a conductor.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The induced voltage in a coil is proportional to the product of the number of loops and the rate at which the magnetic field changes within those loops
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The amount of current produced by electromagnetic induction depends not only on the induced voltage but also on the resistance of the coil and the circuit to which it is connected.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Moving charges experience a force that is perpendicular to both their motion and the magnetic field they transverse.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Deflected wire is the motor effect and the law of induction is the generator effect
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">An electric motor and a generator are effectively the same device, the difference is where the energy is put in and where the energy comes out.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">A motor converts electrical to mechanical and a generator converts mechanical to electrical energy.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Example: think of having two coils that are side by side in which one is connected to a battery and the other is connected to a galvanometer
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The coil connected to the power source is the primary, input, and the other coil is the secondary, output.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The reason that there is only a small connection of current that passed through and when the primary switch is opened, current registers in the opposite direction, the magnetic field that builds up around the primary extends into the secondary coil.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">A transformer is the rate at which the magnetic field changes in the primary is equal to the frequency of the alternating current.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">It can be used to increase or decrease the voltage coming from an alternating current source.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The ratio by which the voltage will change is equal to the ratio of the number of turns on the output coul to the number of turns on the input coil
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">The equation is: power= (voltage * current) sub pri= (voltage* current) sub sec
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Most electric energy sold today is in the form of alternating current (ac) because of the ease with which it can be transformed from one voltage to another.
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Electromagnetic induction is used in terms of the construction of voltages and currents
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">Faraday’s law can be generalized to the case where there may not be a conductor in a changing electric field. It states:
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">“An electric field Is created in any region of space in which a magnetic field is changing with time. The magnitude of the created electric field is proportional to the rate at which the magnetic field changes. The direction of the created electric field is at right angles to the changing magnetic field.”
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">When an electric current is present, it will create a magnetic field, but the changing magnetic field around a changing current will also create an electric field
 * <span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;"><span style="color: #ff0000; font-family: Tahoma, Geneva, sans-serif;">If two field are arranged correctly the result will be electromagnetic waves which are changing electric and magnetic fields that move at the same speed and emphasize each other.