The fundamental frequency of a closed organ pipe
of length 20 cm is equal to the second overtone of
an organ pipe open at both the ends. The length
of organ pipe open at both the ends is :-

A parallel plate air capacitor of capacitance C is
connected to a cell of emf V and then disconnected
from it. A dielectric slab of dielectric constant K,
which can just fill the air gap of the capacitor, is now
inserted in it. Which of the following is incorrect

Which of the following figures represent the
variation of particle momentum and the associated
de-Broglie wavelength ?

A wire carrying current I has the shape as shown
in adjoining figure. Linear parts of the wire are very
long and parallel to X-axis while semicircular portion
of radius R is lying in Y-Z plane. Magnetic field at
point O is :

Consider 3rd orbit of He⁺ (Helium), using non-relativistic approach, the speed of electron in this orbit will be given K = 9×10  constant, Z=2 and h (Planck's Constant) = 6.6×10^-34 Js]

A potentiometer wire has length 4 m and resistance
8Ω. The resistance that must be connected in series
with the wire and an accumulator of e.m.f. 2V, so
as to get a potential gradient 1 mV per cm on the
wire is :