Although direction of current through the armature reverses after each half cycle, yet it keeps on rotating in one direction. Why?

Direct current cannot flow through.

Two parallel wires carryiing current in the same direction attract each other, while two beams of electrons travelling in the same diection repel each other. WHy? Give reasons.

Figure shows a conducting rod PQ in contact with metal rails RP and SQ, which are 0.25 m apart in a uniform magnetic field of flux density 0.4T acting perpendicular to the plane of the paper. Ends R and S are connected through a 5 Omega resistance. What is the emf when the rod moves to the right with a velocity of 5ms^(-1) ? What is the magnitude and direction of the current through the 5 Omega resistance? If the rod PQ moves to the left with the same speed, what will be the new current and its direction?

A uniform magnetic field of 1.5 T exists in a cylindrical region of radius10.0 cm, its direction parallel to the axis along east to west. A wire carrying current of 7.0 A in the north to south direction passes through this region. What is the magnitude and direction of the force on the wire if, the wire in the N-S direction is lowered from the axis by a distance of 6.0 cm?

state the rule to determine the direction of a current induced in a coil due to its rotation in a magnetic field.

A beam of unpolarised ligth is made to fall,from air ,on its boundary with another transparent medium of refrective index mu .The reflected beam is viewed through a rotating analyser.Show on a graph,the variation of intensity of light trasmitted through the analyser with the angel between the pass axis of the analyser and the direction of the reflected beam.

A student performs an experiment to study the magnetic effect of current around a current carrying straight conductor with the help of a magnetic compass. He reports that The direction of deflection of the magnetic compass increases when the current through the conductor is increased. Which of the above observations of the student appears to be wrong and why?