Aptitude Test Problems in Physics Science for Everyone by S Krotov ( PDFDrive.com )

274 Aptitude Test Problems in Physics

Therefore, the required ratio is.

Qi2 i/2+ 3)2,_ + 6

Q34

3.41. Since the anode current is I, the number of

charge carriers (electrons) n arriving at the anode

per unit time can be found from the formula

el

I

I

where e is the charge of a carrier. The momentum

Ap transferred by the charge carriers to the anode

per unit time is

Lp = nmv,

where m is the mass of a carrier, and v. is its veloc-

ity. This momentum is equal to the mean force

exerted on the anode by the charge carriers pre-

cipitating on it. Since mv 2 /2 = I e f U, where

U is the potential difference between the cathode

and the anode, the mean pressure pm exerted by

electrons on the anode can be determined from the

formula

nmv I m 2 lel U

Pm S S lel V^ rn

= I 2mU

S V (^) lel •
3.42. It can be seen that during the time interval
from 0 to to, the voltage across the capacitor is
zero, the charge on it is also zero, there is no cur-
rent through it, and hence UcD is zero during this
time interval (Fig. 221). During the time interval
from to to 2to, the voltage across the capacitor,
and hence the charge on its plates, grows linearly,
and hence a direct current passes through the cir-
cuit. This means that the voltage UcD is constant.
During the time interval from 2t 0 to 3t 0 , the voltage