Unformatted text preview: 240 C , then how long will they last if the radio has a resistance of 200 & ? 6. Serway & Jewett Problem 28 : 43 . Calculate the potential di/erence between points a and b in Figure P 28 : 43 and identify which point is at the higher potential. 7. A voltage source supplies a current I to a parallel combination of resistances R 1 and R 2 . (a) Show that I 1 = IR 2 R 1 + R 2 ; I 2 = IR 1 R 1 + R 2 are the currents in the respective resistors. (b) A copper wire of radius : 250 mm has an aluminum jacket of outer radius : 380 mm . There is a 2 : 00-A current in the composite wire. Calculate the current in each material. In order to calcu-late the necessary resistances, make use of the Table 27 : 2 entitled Resistivities and Temperature Coe¢ cients of Resistivity for Various Materials . 1...
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- Spring '09
- Electrical resistance, Circuit breaker, Jewett Problem