 Fuses and Circuit Breakers are switches that act as safety devices ◦ Addition of appliances reduces the resistance and increases the current ◦ Energy produced enough to melt wires

 Fuse ◦ Short piece of metal that melts ◦ Thickness is determined by amount of current  Circuit Breaker ◦ A Switch that opens and stops current flow when too much has gone through

 There are 10 ohm, 20 ohm, and 60 ohm appliances connected in parallel in a house. A 15 A fuse is connected in series with the power source for the appliances. Will the fuse blow if all appliances are operated at once?

 Equivalent resistance of the appliances  (1/R) = (1/10Ω) + (1/20 Ω) + (1/60 Ω)  = 1/6 Ω = 6 Ω  Find Current of appliances  I = V/R  = 120 V / 6 Ω  = 20 A

 Short circuit starts when there is a very low resistance  If there is a low resistance, what is very large?  Current  Will start a fire in some cases

 Find any parallel resistors. And find the equivalent resistance between them  Now find the equivalent resistance with the other resistors that are in series  Narrow this down until you get one total resistance through a circuit and go backwards to find the current and voltage along single resistors