PHYSICS 7th JAN S-1 2020 - JEE MCQ

Visible light of wavelength 6000 × 10–8 cm falls normally on single slit and produces a diffraction
pattern. It is found that the second diffraction minimum is at 60° from the central maximum. If the first
minimum is produced at (theta)1, then (theta)1 is close to

The radius of gyration of a uniform rod of length l, about an axis passing through a point l/4
away from
the centre of the rod, and perpendicular to it, is

A 60 HP electric motor lifts an elevator having a maximum total load capacity of 2000 kg. If the frictional
force on the elevator is 4000 N, the speed of the elevator at full load is close to : (1 HP = 746 W, g = 10
ms–2)

Two infinite planes each with uniform surface charge density +sigma   are kept in such a way that the angle
between them is 30°. The electric field in the region shown between them is given by

A satellite of mass m is launched vertically upwards with an initial speed u from the surface of the earth.
After it reaches height R(R = radius of the earth), it ejects a rocket of mass
m/10,so that subsequently the
satellite moves in a circular orbit. The kinetic energy of the rocket is (G is the gravitational constant; M
is the mass of the earth) :

A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just
10% of the original intensity. Assuming that the polarizer-analyser set does not absorb any light, the
angle by which the analyser need to be rotated further to reduce the output intensity to be zero is :

A long solenoid of radius R carries a time(t)- dependent current I(t) = I*t(1 – t). A ring of radius 2R is
placed coaxially near its middle. During the time interval 0< t < 1, the induced current (IR) and the
induced EMF(VR) in the ring change as :

12. Which of the following gives a reversible operation ?

Speed of a transverse wave on a straight wire (mass 6.0 g, length 60 cm and area of cross-section 1.0
mm2) is 90 ms–1. If the Young's modules of wire is 16 × 10^(11) Nm^(–2), the extension of wire over its natural
length is

As shown in the figure, a bob a mass m is tied by a massless string whose other end portion is wound
on a fly wheel (disc) of radius R and mass m. When released from rest the bob starts falling vertically.
When it has covered a distance of h, the angular speed of the wheel will be :

A LCR circuit behaves like a damped harmonic oscillator. Comparing it with a physical spring-mass
damped oscillator having damping constant 'b', the correct equivalence would be:

Three point particles of masses 1.0 kg, 1.5 kg and 2.5 kg are placed at three corners of a right angle
triangle of sides 4.0 cm, 3.0 cm and 5.0 cm as shown in the figure. The center of mass of the system is
at a point

The current I1 (in A) flowing through 1ohm  resistor in the following circuit is

If we need a magnification of 375 from a compound microscope of tube length 150 mm and an
objective of focal length 5 mm, the focal length of the eye-piece, should be close to

A litre of dry air at STP expands adiabatically to a volume of 3 litres. If gamma = 1.40, the work done by air is :
(3^(1.4)= 4.6555) [Take air to be an ideal gas]

A parallel plate capacitor has plates of area A separated by distance 'd' between them. It is filled with a
dielectric which has a dielectric constant that varies as k(x) = K(1 + ax) where 'x' is the distance
measured from one of the plates. If (ad) << 1, the total capacitance of the system is best given by the
expression:

Two moles of an ideal gas with Cp/Cv= 5/3 are mixed with 3 moles of another ideal gas with Cp/Cv=4/3 . The
value of Cp/Cv= ?for the mixture is :

A beam of electromagnetic radiation of intensity 6.4 × 10^(–5) W/cm2 is comprised of wavelength,lambda= 310 nm. It falls normally on a metal (work function = 2eV) of surface area of 1 cm2. If one in10^3  photons ejects an electron, total number of electrons ejected in 1 s is 10^x . (hc = 1240 eVnm,1eV =

A particle (m = 1 kg) slides down a frictionless track (AOC) starting from rest at a point A(height 2m).
After reaching C, the particle continues to move freely in air as a projectile. When it reaching its highest
point P(height 1m), the kinetic energy of the particle (in J) is : (Figure drawn is schematic and not to
scale; take g = 10 ms–2) …… .

A loop ABCDEFA of straight edges has six corner points A(0, 0, 0), B(5, 0, 0), C(5, 5, 0), D(0, 5, 0),
E(0, 5, 5) and F(0, 0, 5). The magnetic field in this region is B=( 3!^+4j^)T
The quantity of flux through
the loop ABCDEFA (in Wb) is …….

A non-isotropic solid metal cube has coefficients of linear expansion as : 5 × 10^(–5) /°C along the x-axis
and 5 × 10^(–6) /°C along the y and the z-axis. If the coefficient of volume expansion of the solid is
C × 10^(–6)/°C then the value of C is …….. .

A carnot engine operates between two reservoirs of temperatures 900 K and 300 K. The engine
performs 1200 J of work per cycle. The heat energy (in J) delivered by the engine to the low
temperature reservoir, in a cycle, is …….