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

266 Aptitude Test Problems in Physics

The voltage across the load will be

R 2

= - 5 - U.

If the resistance of the load becomes equal to 2R,
the total current will be

10 U

1

2

.

R L (R/2) (2R) ---- 9 R •

2 m R/2-F2R

The voltage across the load will become

U—/2

R 4

u

Thus, the voltage across the load will change by

a factor of k = ( (^1211) Ui1:
k=U 21 10
U 11 9
3.30. In the former case, the condition / 1 =-- I
is fulfilled, where / 1 = aini and / 2 = a 2 n 2. Con-
sequently, aini = a 2 n 2. In the latter case, riRi
I;Rx, where Rx is the resistance of the second
resistor. Besides, /; = ain; and /; = a 2 n;, and
hence
Rlalnt = fixa 2 n;.
Finally, we obtain
/lin; Rxr4
nl (^) n 2
Therefore,
Rin 2 ni
Rx — (^) • •
nin 2
3.31. The condition required for heating and melt-
ing the wire is that the amount of Joule heat
liberated in the process must be larger than the
amount of heat dissipated to the ambient:
12 R > kS (T — Tam).