Please show your work. Only part C & D for 750. A & B posted elsewhere. How many

Question

Please show your work.

Only part C & D for 750.

A & B posted elsewhere.

How many electrons strike the screen each second? The electron beam inside a television picture tube is 0.500mm in diameter and carries a current of 53.0 mu A. This electron beam impinges on the inside of the picture tube screen. What is the current density in the electron beam? The electrons move with a velocity of 4.30Times107 m/s. What electric field strength is needed to accelerate electrons from rest to this velocity in a distance of 4.00mm ? Each electron transfers its kinetic energy to the picture tube screen upon impact. What is the power delivered to the screen by the electron beam?

Explanation / Answer

a)

Number of electrons for 1 second

Ne =(I/e)*t

Ne=(53*10^-6)/(1.6*10^-19)

Ne=3.3125*10^14 electrons/second

b)

r=d/2 =0.25 mm

Area

A=pi*r^2 =pi*(0.25*10^-3)^2

A=1.963*10^-7 m^2

Current density

J=I/A =(53*10^-6)/(1.963*10^-7)

J=269.93 A/m^2

c)

Vf^2=Vi^2+2ad

(4.3*10^7)^2=2*a*(4*10^-3)

a=2.3*10^17 m/s^2

since

F=ma=qE

E=ma/q =(9.11*10^-31)*(2.3*10^17)/(1.6*10^-19)

E=1.316*10^6 N/C

d)

KE=(1/2)*m*V^2

KE=(1/2)*(9.11*10^-31)*(4.3*10^7)^2

KE=8.42*10^-16 J

Power Just measure how fast energy changes

P=KE*(Ne/t)

P=8.42*10^-16*(3.3125*10^14)/1

P=0.2638 Watts

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---