If the wavelength of the first of the Balmer series of hydrogen is 6561 Å, the wavelength of the second line of the series should be
Which of the following has the mass closest in value to that of the positron
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Energy needed to establish an alternating current I in a coil of self inductance L is
An ammeter reads upto 1 ampere. Its internal resistance is 0.81 ohm. To increase the range to 10 A the value of the required shunt is
The current in a conductor varies with time t as I = 2t + 3t2 where I is in ampere and t in seconds. Electric charge flowing through a section of the conductor during t = 2 sec to t = 3 sec is
When an inert gas is filled in the place vacuum in a photo cell, then
A straight conductor of length 0.4m is moved with a speed of 7 ms⁻1 perpendicular to a magnetic field of induction 0.9 Wb/m2. The induced e.m.f. across the conducor is
Turn ratio is 1: 25. The step up transformer operates at 230 V and current through secondary is 2A. Then current in primary is
A black body is heated from 27°C to 127°C. The ratio of their energies of radiations emitted will be
A geostationary satellite orbits around the earth in a circular orbit of radius 36000 km. The time-period of a spy satellite orbiting a few hundred kilometers above the earth's surface will approximately be (Radius of earth = 6400 km).
An infinite number of charge of equal magnitude q, but of opposite sign are placed along the X-axis at x = 1, x = 2, x = 4, x = 8... and so on. The electric potential at the point x = 0 due to these charge will be
A polyatomic gas with n degrees of freedom has a mean energy per molecule given by
Capacitance of a capacitor becomes 7/6 times its original value if a dielectric slab of thickness, t = 2/3 d is introduced in between the plates. 'd' is the separation between the plates. The dielectric constant of the dielectric slab is
For a body moving with constant speed in a horizontal circle, which of the following remains constant ?
If a person with a spring balance and a body hanging from it goes up and up in an aeroplane, then reading of weight of body as indicated by spring balance will
At 100 K and 0.1 atmospheric pressure, the volume of helium gas is 10 litres. If volume and pressure are doubled, its temperature will change to
A galvanometer of resistance 98 Ω is shunted by a resistance of 2 Ω . The fraction of total current that passes through the galvanometer is
An incompressible fluid flows steadily through a cylindrical pipe which has radius 2 R at point A and radius R at point B. If velocity at point A is ν, then its velocity at point B is
A 20 cm long capillary tube is dipped in water. The water rises up to 8 cm. If entire arrangement is put in a freely elevator, the length of water column in the capillary tube will be
Two water pipes P and Q having diameters 2 cm and 4 cm respectively are joined in series with the main supply line of water. The velocity of water flowering in pipe P is
A tank of height 5 m is full of water. There is a hole of cross-sectional area 1 cm2 in its bottom. Initial volume of water that will flow through the hole is (Take g = 10 m-s⁻2)
A body floats in a liquid contained in a beaker. If the whole system falls under gravity, then the upthrust on the body due to liquid is
Oil spreads over the surface of water, whereas water does not spread over the surface of oil, because
Two similar wires under the same load yield elongations of 0.1 mm and 0.05 mm respectively. If the area of cross-section of the first wire is 4 mm2, then the area of cross-section of the second wire is
According to the Hooke's law, if stress is increased, then ratio of stress to strain
A sphere of mass m is tied to end of a string of length l and rotated through the other end along a horizontal circular path with speed υ. The work done in full horizontal circle is
If a train travelling at 72 kmph is to be brought to rest in a distance of 200 metres. then its retardation should be
In a compound microscope, the focal lengths of objective lens and eye piece are 1 cm and 2 cm respectively. If tube length of the microscope is 20 cm, then magnifying power of microscope will be