- An alpha particle of energy 5 MeV is scattered
through 180° by a xed uranium nucleus. e
distance of closest approach is of the order of
(a) 1Å (b) 10 –10 cm
(c) 10 –12 cm (d) 10 –15 cm - A triode has plate characteristics in the form
of parallel lines in the region of our interest.
At a grid voltage of –1 volt the anode current I
(in milli ampere) is given in terms of plate voltage V
(in volt) by the algebraic relation: I = 0.125V – 7.5
For grid voltage of –3 volt, the current at anode
voltage of 300 V is 5 mA. Determine the plate
resistance (rP) and the transconductance (gm) for
the triode.
(a) 8 × 10^3 :, 22.5 × 10–3 A V–1
(b) 4 × 10^8 :, 12.5 × 10–6 A V–1
(c) 8 × 10^3 :, 12.5 × 10–3 A V–1
(d) None of these - A radioactive material decays by simultaneous
emission of two particles with respective half-lives
1620 and 810 year. e time, in year, aer which
one-fourth of the material remains is
(a) 1080 (b) 2430 (c) 3240 (d) 4860 - e two rails of a railway track, insulated from
each other and the ground, are connected to
a millivolt meter. What is the reading of the
milli voltmeter when a train travels at a speed of
170 km h–1 along the track, given that the horizontal
components of earth’s magnetic eld is 0.2 × 10–4
wb^ m–2 and the rails are separated by 1 m?
(a) 2.5 mV (b) 3.56 mV
(c) 1.8 mV (d) 0.944 mV - A copper wire is stretched to make it 0.2 % longer.
What is the percentage change in its resistance?
(a) 0.3 (b) 0.4 (c) 0.8 (d) 0.2 - In an experiment of simple pendulum time period
measured was 50 s for 25 vibrations when the length
of the simple pendulum was taken 100 cm. If the
least count of stop watch is 0.1 s and that of meter
scale is 0.1 cm. Calculate the maximum possible
error in the measurement of value of g.
(a) 1.5% (b) 0.75% (c) 2.5% (d) 0.5% - e following observations were taken for
determining surface tension of water by capillary
tube method. Diameter of capillary D = 1.25 × 10–2m
and rise of water in capillary, h = 1.45 × 10–2 m. Taking
g = 9.80 m s–2 and using the relation
T=rgh
2× 10^3 N m –1, what is the possible error
in measurement of surface tension T?
(a) 2.4% (b) 15% (c) 1.6% (d) 0.15%- A student performs an experiment to determine
the Young’s modulus of a wire, exactly 2 m long, by
Searle’s method. In a particular reading, the student
measures the extension in the length of the wire to
be 0.8 mm with an uncertainty of r 0.05 mm at a
load of exactly 1.0 kg. e student also measures
the diameter of the wire to be 0.4 mm with an
uncertainty of ± 0.01 mm. Take g = 9.8 m s–2 (exact).
e Young’s modulus obtained from the reading is
(a) (2.0 r 0.3) × 10^11 N m–2
(b) (2.0 r 0.2) × 10^11 N m–2
(c) (2.0 r 0.1) × 10^11 N m–2
(d) (2.0 r 0.05) × 10^11 N m–2. - In a screw gauge, the zero of main scale coincides
with h division of circular scale in gure (i). e
circular division of screw gauge are 50. It moves
0.5 mm on main scale in one rotation. e diameter
of the ball in gure (ii) is
(^030)
(^2520)
Figure (ii)
(^010)
(^50)
Figure (i)
(a) 2.25 mm (b) 2.20 mm
(c) 1.20 mm (d) 1.25 mm
- During an experiment with a metre bridge, the
galvanometer shows a null point when the jockey
is pressed at 40.0 cm using a standard resistance
of 90 :, as shown in the gure. e least count
of the scale used in the metre bridge is 1 mm. e
unknown resistance is
(a) 60 r 0.15 :
(b) 135 r 0.56 :
40.0 cmR^90 Ω(c) 60 r 0.25 :
(d) 135 r 0.23 :- A student performed the experiment to measure the
speed of sound in air using resonance air-column
method. Two resonances in the air-column were
obtained by lowering the water level. e resonance
with the shorter air-column is the rst resonance
and that with the longer air column is the second
resonance. en,
(a) the intensity of the sound heard at the rst
resonance was more than that at the second
resonance