Find the current in the 36.0-Ω resistor.

+2 votes

Consider the circuit shown in the figure below. (Let R = 36.0 Ω.)

image
(a) Find the current in the 36.0-Ω resistor.
  A

(b) Find the potential difference between points a and b.
  V

 

asked Feb 9, 2012 in Physics by awesome ~Expert~ (1,479 points)
    

1 Answer

+2 votes
 
Best answer

First redraw the circuit as follows:

image

 

Now find Rii, which is

Rii = 5 + R = 5 + 36 = 41Ω

 

The first step is to combine the resistors and find the total resistance:

First find Riii,

Riii = Rii // 5Ω// 10Ω  =  41Ω // 5Ω //10Ω  (* // = parallel)

Riii = 1 / (1/10 + 1/5 + 1/41) = 3.081 Ω

Riv = 10 + Riii = 13.081 Ω

 

I = V / Riv  = 25 / 13.083 =  1.91 A

Now find the voltage going through the points a and b,

V = I*Riii = 1.91*3.083  =   5.89 V

Now the current through R can be found, by using the following formula:

I = Vab / Rab  = 5.89V / (R +5)  =  5.89V / (36 +5)  =    0.1437  A

 

and part B was already calculated above to be  5.89 V

 

 

answered Feb 9, 2012 by pokemonmaster ~Expert~ (3,856 points)
selected Feb 9, 2012 by awesome



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