Solution 5

Chapter 10 Electronics

Exercises  1,2,19,20,21
 

E1. The power of the signal from a microphone is very small and not able to drive the speaker with enough energy.

E2. Because to boost the power the power (and therfore energy) must come from somewhere. The battery or power supply is what provides this energy.

E19. The "6" means there are 6 one hundreds in this number.

E20. The left most 1 in 101 means there are 1 4's. the third place represents the 2^2 place or 4's place.

E21.  11011011 binary = 219 decimal
         01010101 binary = 85 decimal
 
 

Chapter 11 Electromagnetic Waves

Exercises  9,10,12,15,23,25,26,30
Problems 1,3,5
 

E9. Because the main center frequency has its frequency modulated by the audio signal. If its frequency was too close to an adjacent station the modulation of the main carrier frequncy would cause them to overlap and interfere at the receiver.

E10. Because heavy use of the phones by other people will crowd the available chanels or frequncies. Each phone/base unit must operate on an idependent frequency to avoid interference from other close by phones.

E12. The AM station is Amplitude Modulated. If it is far away during the peak of the modulation you may have enough signal to receive it. With FM the amplitude is not modulated. Once you are too far away and the signal is weak you will lose the ability to receive the signal.

E15. This is the frequency that Microwave ovens generate their EM waves at. This would cause inteference from any leaking of the signal out of the microwave oven.

E23. The bending of the electrons in the TV tube by the magnetic field acting on the charged electrons. This deflects the electrons from their intended phosphor dot and cause a distorted image in that location.

E25. Because the water absorbed in the ceramic would get heated by the microwaves and cause damage.

E26. Because if it were aluminum the metal would deflect the microwaves and may cause uneven heating. Also, sharp points or edges in the aluminum would cause large electric fields and electical arcing with potential damage to the microwave.

E30. Because as long as the mesh has holes small compared to the wavelength of the EM wave they act like solid metal sheet in reflecting the wave.

P1. recall that speed of em waves C = wavelength x frequency.  So, wavelength = C/freq = 3x10^8 m/s  / 900x10^6 1/s = 0.33 meters

P3. Again using   speed = wavelength x freq
 we get wavelength = c/freq = 4.62x10^-7 meters or 462 nanometers

P5. c = wavlngth x freq
        freq = c/ wavelength = 3x10^8 m/s /.36m = 833 x 10^6 1/s = 833 megaHertz = 833 MHz