1. The length of a 60 W, 240 ? light bulb filament is 60 cm. A) If the potential

Question

1.       The length of a 60 W, 240 ? light bulb filament is 60 cm.

A) If the potential difference across the filament is 120 V, what is the strength of the electric field inside the filament?____V/m

B)Suppose the length of the bulb's filament were doubled without changing its diameter or the potential difference across it. What would the electric field strength be in this case? ____V/m

C)Remembering that the current in the filament is proportional to the electric field, what is the current in the filament following the doubling of its length?____A

D)What is the resistance of the filament following the doubling of its length?________ ohm

2.       The biochemistry that takes place inside cells depends on various elements, such as sodium, potassium, and calcium, that are dissolved in water as ions. These ions enter cells through narrow pores in the cell membrane known as ion channels. Each ion channel, which is formed from a specialized protein molecule, is selective for one type of ion. When an ion channel opens in a cell wall, monovalent (charge e) ions flow through the channel at a rate of 1.0

Explanation / Answer

1. a. E =V/d   = 120/0.6 = 200 V/m

b.. since EF is inversly proportional to L, if L doubles, E reduces to half = 100 V/m

c. if V reduced to half = 60 volts

as power =Vi -----> i = 60/60 = 1Amps

d. as V =iR,---------> R = 60/1 = 60 ohms

2. charge q = ne --------> 10^7 *1.6*10^-19 =1.6*10^-12 C/s = 1.6 pAmps

b. power = Vi = 0.070 * 1.6*10^-12 =1.12*10^-13 Watts

3.power = energy/time-------> time =6100/(1.6*1.5) =2541.2 secs   = 42.36 min

4.

5. R = rho L/A

R = 1*10^-6* 0.55/(3.14* 0.4*0.4*10^-6) =1.1 ohms

then i = V/R = 8/1.1 =7.272 amps

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