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 :

On observing light from three different stars P, Q
and R, it was found that intensity of violet color is
maximum in the spectrum of P, the intensity of green
colour is maximum in the spectrum of R and the
intensity or red colour is maximum in the spectrum
of Q. If T_P, T_Q and T_R are the respective absolute
temperatures of P, Q and R, then it can be
concluded from the above observation that :

Across a metallic conductor of non-uniform cross
section a constant potential difference is applied.
The quantity which remains constant along the
conductor is :

For a parallel beam of monochromatic light of
wavelength 'λ', diffraction is produced by a single
slit whose width 'a' is of the order of the wavelength
of the light. If 'D' is the distance of the screen from
the slit, the width of the central maxima will be :