148 Direct Current CircuitsP28.49(a)P=IV∆:So for the Heater,IV===∆150012 5W120 VA..For the Toaster,I750625W120 VAAnd for the Grill,I1000833W120 VA(b)12 5 6 25 8 3327 1..++=AThe current draw is greater than 25.0 amps, so this circuit breaker would not be sufficient.P28.50IRI RAl2AlCu2Cu=soIRRIIAlCuAlCuCuAlCuA=====ρ17028220 00 776 20 015 5....afafP28.51(a)Suppose that the insulation between either of your fingers and the conductor adjacent is achunk of rubber with contact area 4 mm2and thickness 1 mm. Its resistance isRA=≈⋅×≈×−−A1010410210133615m mm2ΩΩejej.The current will be driven by 120 V through total resistance (series)01005101541515×++×ΩΩΩΩ.It is: IVR=×−∆Ω~~1201014V0 A15.(b)The resistors form a voltage divider, with the center of your hand at potential Vh2, where Vhis the potential of the “hot” wire. The potential difference between your finger and thumb is∆ΩVIR=−−10101014410A Vej. So the points where the rubber meets your fingers are
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .