Physics chap 23

• Induction - the process of generating currents with magnetic fields
• Magnetic flux - Greek letter I = BAcos(theta)

  Units : Tm^2
• Any change in magnetic flux induces an emf (electromagnetic flux)
• Faraday's Law of Induction - emf=-N(delta phi/delta t)

  Units: V
• Lenz's Law - The emf creates a current I and magnetic field B that opposes the change in flux
• Motional emf - motion in a magnetic field that is stationary relative to the earth
• Transformers transform voltages from one value to another
• 2 coils : primary and secondary
• The input voltage is placed on the primary coil, and the secondary produces the transformed output voltage
• step-up transformer increase voltage
• step-down transformer - decreases voltage
• Transformers can NOT be used for DC voltages
• Transformer equation: Vs/Vp=Ns/Np
• Thermal hazard occurs when there is electrical overheating
• Shock hazard occurs when electric current passes through a person
• A ground fault interrupter (GFI) compares the currents in the live and neutral wires and will trip if their difference exceeds a safe value
• Inductance is the process is which an emf is induced by a changing magnetic flux

  Units: Henry (H)
• Mutual inductance is the effect of Faraday's law of induction for one device upon another
• 1 H = 1 Ohm * S
• Self inductance is the effect of Faraday's law of induction of a device on itself