Please show your work and answer ALL of the questions correctly. (a) What is the

Question

Please show your work and answer ALL of the questions correctly.

(a) What is the current when the potential difference between the walls is 105 mV?
A

(b) If the current is composed of Na+ ions (q = +e), how many such ions flow in 1 s?
ions

2.) Three resistors, 29, 47, and 81 ?, are connected in series, and a 0.47-A current passes through them.

(a) What is the equivalent resistance?
________?

(b) What is the potential difference across the three resistors?
___________V

3.) A light bulb is wired in series with a 145-? resistor, and they are connected across a 120-V source. The power delivered to the light bulb is 24.2 W. What are the two possible resistances of the light bulb?

Explanation / Answer

1.)

a.) I = V/R = (105*10^-3)/(1.8*10^10) = 5.833 x 10^-12 A

b.) i = q/t

q = i*t = (5.833 x 10^-12)(1) = 5.833 x 10^-12 C

No of Na+ ions = (5.833 x 10^-12 C)/(1.602 x 10^-19 C) = 36412817

2.)

a.) Req = 29+47+81 = 157 ohms

b.) V = I*Req = (157)(0.47) = 73.79 V

3.)

Let the resistance of the light bulb be 'r'

I = 120/(145+r)

P of light bulb = (120/(145+r))^2*r = 24.2

Solving, we get

r = 105.22 (or) 199.82

So lower value = 105.22 ohms

So higher value = 199.82 ohms

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