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Chapter 37 Electromagnetic Induction: Faraday’s Law What is electromagnetic induction? Electromagnetic induction: The phenomenon of inducing a voltage in a How can magnetism create electricity? When a magnet is plunged into a coil, voltage is induced and the charges in the coil are set in motion What determines the amount of EM induction? Amount of induction depends on rate of motion and number of coils. What happens to the magnetic field as the # of coils increase? As the number of coils increase, the magnetic field also increases. This makes pushing the magnet through more difficult. State Faraday’s Law 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 Explain why Faraday’s Law only applies to voltage. Applies only to voltage because current is determined by the resulting voltage and the resistance of the conductor. conductor by changing the magnetic field near the conductor Current as well as voltage is induced in a wire by electromagnetic induction. Why then is Faraday’s Law expressed in terms of induced voltage and not current? Summary Chapter 37 Electromagnetic Induction: Induction of EM Fields What is a transformer? A transformer is a device for increasing or decreasing voltage through EM induction Two coils, one with a voltage source (primary) and one with a meter How do transformers work? (secondary) stand in close proximity. When current changes in the primary coil (turning on and off a switch), the changing magnetic field that builds up in the primary coil will extend to the secondary coil. If an iron core is placed inside both coils, the effect is intensified. By using alternating current, the current changes automatically (you don’t have to keep switching on and off). How can transformers modify voltage? By changing the number of loops on either the primary or the secondary, voltage can be in creased or decreased. What is the relationship between primary and secondary voltages with respect to # of turns? Can energy (power) be increased through this process? Why or why not? What does Faraday’s law say about changing magnetic fields? What is the corollary to Faraday’s law? How are all electromagnetic waves generated? At what speed must EM waves travel in order to maintain induction? Ohm’s Law Applies: As voltage increases, current decreases power is the same A changing magnetic field creates a proportional electric field. The created electric field is at right angles to the changing magnetic field. A changing electric field creates a proportional magnetic field. The created magnetic field is at right angles to the changing electric field. Shaking a charged stick will create a changing electric field. At the speed of light 300,000 km/s Explain why it is better to transmit energy at very high voltages instead of low voltages. Summary