Answers for Assignment 10

51. Proof

52. The EMF is called V in these answers; the text's answer for I₂ in part (c) has the wrong sign.

Part	I1	I2
(a) t=0, switch closed	V/( R1 + R2 )	V/( R1 + R2 )
(b) t=infinity, switch closed	R2 + R3 V ----------------- R1(R2 + R3) + R2R3	R3 V ----------------- R1(R2 + R3) + R2R3
(c) t=new 0, switch reopened	0	R2 - V ----------------- R1(R2 + R3) + R2R3
(d) t=infinity, switch reopened	0	0

53.

(a) V / L₁ and V / L₂ , respectively

(b) V / R

54. In this answer e=2.71828..., not q _electron.

            L V2 
   (a) W  = ----       Energy supplied by battery.
            e R2
   
                L V2    
   (b) WR  = -  ---- ( 1 - 4/e + 1/e2 )  Energy dissipated in resistor.
                2 R2
              
                L V2          
   (c) WL  =    ---- ( 1 - 2/e + 1/e2 )  Energy stored in inductor
                2 R2

   Try adding WR and WL .  What explains the result?

Last revised 1998/04/27