The force on a north pole, `vec F = m vec B`, is parallel to the field `mvec B`, is parallel to the field `vet B`. Does it contradict our earlier knowledge that a magnetic field can exert forces only perpendicular to itself?

A U-shaped conducting frame is placed in a magnetic field B in such a way that the plane of the frame is perpendicular to the field lines. A conducting rod is supported on the parallel arms of the frame, perpendicular to them and is given a velocity v_0 at time t = 0. Prove that the velocity of the rod at time t will be given by v_t=v_0 "exp" ((-B^2l^2)/(mR)t) .

Any charge is moving parallel and antiparallel to magnetic field, then what is magnetic force on it ?

A circular coil of 20 turns and radius 10 cm is placed in a uniform magnetic field of 0.10 T normal to the plane of the coil. If the current in the coil is 5.0 A, what is the (a) total torque on the coil, (b) total force on the coil, (c) average force on each electron in the coil due to the magnetic field? (The coil is made of copper wire of cross-sectional area 10^(-5) m^2 , and the free electron density in copper is given to be about 10^29 m^(-3) .)

If vec(E ) and vec(B) represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of electromagnetic wave is along

The following figure shows the magnetic field between two magnets . Which magnetic poles are there at points A and B respectively ?

An electron enters with a velocity vecv,v_(0)hati into a cubical region (faces parallel to coordinate planes) in which there are uniform electric and magnetic fields. The orbit of the electron is found to spiral down inside the cube in plane parallel to the x-y plane. Suggest a configuration of fields E and B that can lead to it.

It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small flat search coil of area 2 "cm"^2 with 25 closely wound turns, is positioned normal to the field direction, and then quickly snatched out of the field region. Equivalently, one can give it a quick 90^@ turn to bring its plane parallel to the field direction). The total charge flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5 mC. The combined resistance of the coil and the galvanometer is 0.50 Omega . Estimate the field strength of magnet.