I have three questions. Please answer them all throughly and with all the work s
ID: 1396478 • Letter: I
Question
I have three questions. Please answer them all throughly and with all the work shown.
(1)Two closely spaced circular disks form a parallel-plate capacitor. Transferring 1,727,962,392.372 electrons from one disk to the other causes the electric field strength to be 1,775,120,723.199 N/C. What are the diameters of the disks?
(2)A charge of 3.295 nC is moved from a position on the y axis of 4.879 cm to a position on the x axis of 1.64 cm while there is a charge 22.039 located at the origin. How much work in micro-Joules did it take to move the charge?
(3)Moving a charge from point A, where the potential is 398.3489 V, to point B, where the potential is 174.4013 V, takes 0.0005 J of work. What is the value of the charge?
Explanation / Answer
1) here one disk gets poitive charge onother disk gets negative charge.
magnitude of charge on disk, Q = 1727962392.372*1.6*10^-19
= 2.76*10^-10 C
we know, eletric filed between plates, E = Q/(A*epsilon)
==> A = Q/(E*epsilon)
= 2.76*10^-10/(1775120723*8.854*10^-12)
= 1.756*10^-8 m^2
we know, A = pi*d^2/4
==> d = sqrt(4*A/pi)
= sqrt(4*1.756*10^-8/pi)
= 1.495*10^-4 m or 0.1495 mm
2) workdone = U2 - U1
= k*q1*q2/r2 - k*q1*q2/r1
= k*q1*q2*(1/r2 - 1/r1)
= 9*10^9*3.295*10^-9*22.039*10^-9*(1/0.0164 - 1/0.04879)
= 2.65*10^-5 J
3) W = delta V*q
==> q = W/delta V
= 0.0005/(398.3489 - 174.4013)
= 2.23*10^-6 c