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Ch19-h1-problems-6

# Ch19-h1-problems-6 - yoon(jey283 Ch19-h1 turner(56545 This...

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yoon (jey283) – Ch19-h1 – turner – (56545) 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points Why does the the brightness of a bulb not change noticeably when you use longer copper wires to connect it to the battery? A. Very little energy is dissipated in the thick connecting wires. B. The electric field in the connecting wires is very small, so emf E bulb L bulb . C. The electric field in the connecting wires is zero, so emf = E bulb L bulb . D. The current in the connecting wires is smaller than the current in the bulb. E. All the current is used up in the bulb, so the connecting wires don’t matter. 002(part1of5)10.0points The following questions correspond to the fig- ure shown, consisting of two flashlight bat- teries and two Nichrome wires of different lengths and different thicknesses as shown (corresponding roughly to your own thick and thin Nichrome wires). + + The thin wire is 51 cm long, and its diame- ter is 0 . 18 mm. The thick wire is 24 cm long, and its diameter is 0 . 37 mm. The emf of each flashlight battery is 1 . 6 V. Determine the steady-state electric field in- side each Nichrome wire. Remember that in the steady state you must satisfy both the current node rule and energy conservation. These two principles give you two equations for the two unknown fields. Find the electric field in the thin wire first. Answer in units of V / m 003(part2of5)10.0points Find the electric field in the thick wire. Answer in units of V / m 004(part3of5)10.0points How long does it take an electron to drift through both Nichrome wires if electron mo- bility in Nichrome is 0 . 0001 (m / s)(N / C). Answer in units of s 005(part4of5)10.0points On the other hand, about how long did it take to establish the steady state when the circuit was first assembled? 1. 2 . 5 s 2. 2 . 5 × 10 - 9 s 3. 2 . 5 × 10 - 6 s 4. 2500 s 5. 0 . 0025 s 006(part5of5)10.0points There are about 7 × 10 28 mobile electrons per cubic meter in Nichrome. How many electrons cross the junction between the two wires every second?

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Ch19-h1-problems-6 - yoon(jey283 Ch19-h1 turner(56545 This...

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