As per this diagram a point charge +q is placed at the origin O. Work done in taking another point charge -Q from the point A [coordinates (O, a)] to another point B [coordinates (a, O)] along the straight path AB is
zero
If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by respectively, then
C.
..In diamagnetic substances in each pair of electrons, the spin of both the electrons are in opposite directions. Hence, the electrons of each pair completely cancel the magnetic moment of each other. Thus, the net magnetic moment of each atom of such substances is zero i.e., .
The property of paramagnetism is found in those substances whose atoms, or molecules have an excess of electrons spinning in the same direction. Hence, atoms of paramagnetic substances have permanent magnetic moment ie, . The property of ferromagnetism is found in substances which acquire very strong magnetism when placed in an external magnetic field. Like the paramagnetic substances each atom of ferromagnetic substances also has a also has a permanent magnetic moment i.e, .
In a circuit, L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is
When a wire of uniform cross-section a, length land resistance R is bent into a complete circle, resistance between two of dimetrically opposite points will be
4R
An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional, to
B/v
v/B
√v/B
√B/v
In the reaction, if the binding energies of are respectively a, b and c (in MeV), then the energy in this reaction is released in this reaction is
c + a - b
c - a - b
a + b + c
a +b - c
The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein's equation, the metals which will emit photoelectrons for a radiation length 4100 Ao is /are
none
A only
A and B only
all the three metals