QUIZ 3

1. Calculate the current passing through the 2.00W resistor in the circuit as shown.

 Solution. We find the equivalent resistance of the circuit:

                The given circuit reduces as shown in the figures, 

                3.00W and 1.00W  resistance can be combined to:

                1/[(1/1.00W) + (1/3.00W)] = 0.750W 

                The circuit can be reduced as Fig. (a)

               We find the equivalent resistance of the circuit in Fig (b):

                 Req = 2.00W + 0.750W + 4.00W = 6.750W

               Apply Ohm's law we find the current passing through 2.00W resistor :

                 I = (18.0V)/(6.75W) = 2.67A.

                

 

                         
 

2. In the previous circuit calculate the power dissipated in each resistor.

    Solution. From the previous problem the current passing through the 2.00W and 4.00W resistors is 2.67A, so we have

                                P2 = I2R = (2.67A)2(2.00W) = 14.2W

                                P4 = I2R = (2.67A)2(4.00W) = 28.4W

                  The voltage across the 0.750W in (a), and across both the 3.00W and the 1.00W resistor  is

                                V = IR = (2.67A)(0.750W) = 2.00V

                   Then for the 3.00-W resistor, 

                                P3 = V2/R = (2.00V)2/3.00W) = 1.33W;

                    For the 1.00W resistor:

                                P1 = V2/R = (2.00V)2/(1.00W) = 4.00W