A metallic prong consists of 4 rods made of the
same material, cross-section and same lengths as
shown.[2013][2010][2012][2012][2012]7.[2012]8.[2011]1]Waves on String
1.[2017]Sound Waves
1.[2016]2.[2015]The three forked ends are kept at 100 Cand the
handle end is at 0 C.The temperature of the junc-
tion is
(a) 25 C (b) 50 C (c) 60 C (d) 75 C
A piece of hot copper at 100ºC is plunged into a
pond at 30ºC. The copper cools down to 30ºC,
while the pond, being huge,stays at its initial tem-
perature. Then
(a) Copper loses some entropy, the pond stays
at the same entropy
(b) Copper loses some entropy, and the pond gains
exactly the same amount of entropy
(c) Copper loses entropy, and the pond gains more
than this amount of entropy
(d) Both copper and the pond gain in entropy
A steady current I flows through a wire of radius r,
length L and resistivity . The current produced
heat in the wire. The rate of heat loss in a wire is
proportional to its surface area. The steady tem-
perature of the wire is independent of
(a) L (b) r (c) I (d)
Two identical bodies are made of a material for
which the heat capacity increases with tempera-
ture. One of these is held at a temperature of 100ºC
while the other one is kept 0º C. If the two are
brought into contact, then, assuming no heat loss
to the environment, the final temperature that they
will reach is
(a) 50º C (b) Less than 50º C
(c) More than 50º C (d) 0º C
A cylindrical steel rod of length 0.10 m and thermal
conductivity 50 .W m K ^11 is welded end to end to
copper rod of thermal conductivity 400. .W m K^1 ^1
and of the same area of cross section but 0.20 m
long. The free end of the steel rod is maintained at
100º C and that of the copper and at 0º C. Assum-
ing that the rods are perfectly insulated from thesurrounding, the temperature at the junction of the
two rods is
(a) 20º C (b) 30º C (c) 40º C (d) 50º C
The total energy of a black body radiation source is
collected for five minutes and used to heat water.
The temperature of the water increases from
10.0º C to 11.0ºC. The absolute temperature of the
black body is doubled and its surface area halved
and the experiment repeated for the same time.
Which of the following statements would be most
nearly correct?
(a) The temperature of the water would increase
from 10.0º C to a final temperature of 12º C
(b) The temperature of the water would increase
from 10.0º C to a final temperature of 18º C
(c) The temperature of the water would increase
from 10.0º C to a final temperature of 14ºC
(d) The temperature of the water would increases
from 10.0º C to a final temperature of 11º C
The total radiative power emitted by spherical black-
body with radius R and temperature T is P. If the
radius if doubled and the temperature is halved
then the radiative power will be
(a) P/4 (b) P/2 (c) 2P (d) 4PA transverse wave of frequency 500Hz and speed
100m/s is travelling in the positive x direction on a
long string. At t0s the displacements at
x0.0m and at x0.25m are 0.0 m an 0.02m,
respectively. The displacement at x0.2m at
t 5 10^4 s is
(a) -0.04 m (b) -0.02 m (c) 0.04 m (d) 0.02 mA hearing test is conducted on an aged person. It
is found that her threshold of hearing is 20 deci-
bels at 1kHz and it rises linearly with frequency to
60 decibles at 9kHz. The minimum intensity of sound
that the person can hear at 5 kHz is
(a) 10 times than that at 1khz
(b) 100 times than that at 1 khz
(c) 0.5 times than that at 9 khz
(d) 0. 05 times than that at 9 khz
The intensity of sound during the festival season
increased by 100 times. This could imply a decible
level rise from
(a) 20 to 120 dB (b) 70 to 72 dB
(c) 100 to 10000dB (d) 80 to100dB