Exercise Solutions

 

 

Problem 4

This is a simple application of Ohm's law      V = IR

V and R are given so R = V/I = 120 V/1.2 A = 29 W

Problem 5

Another simple application of Ohm's law   V = IR

I and R are given so V = IR = (0.25 A)(3800 Ohms) = 950 V

Problem 13

We know that the resistivity is given by rL/A  so we need to find A and look up the constant of proportionality (r)                       

A = pd²/4                

R =  rL/A =  rL4/pd² = (1.68x10^-8 Wm)(4)(3.5 m)/p(1.5x10^-3 m)² = 0.033 W

 

Problem 14

 

As shown above, R =  rL/A =  rL4/pd² 

 

So, we simply find the ratio = 1.2

 

Problem 27

P = IV = 0.96 W

                       

Problem 28

 

P = V²/R  ð  V = (RP)^1/2 = 26 V

 

 

Problem 43

 

I_peak = V_peak/R = 0.55 A

 

I_rms = I_peak/(2)^1/2 = 0.39 A