amit said:1.CURRENT ELECTRICITY
1.although direction is associated with current,it is not a vector as the direction merely gives an idea about the way the charge is flowing inside the conducting material.
2.often a question arises in people's minds that why a capacitor can't be used as a battery since it also maintains a potential difference between its two plates..the reason is that the potential difference maintained is not constant.a capacitor discharges very quickly once the current is fully build up and hence is not able to maintain a constant potential difference like a battery.
2.ELECTROSTATICS
1.work done by external forces is always opposite to the work done by electric forces in an electric field.
2.equipotential surfaces and field lines through them are always mutually perpendicular.
3.if a symmetrical body( like a cube) has n identical faces with point charge at its centre,flux linked with each face will be q/n(nought).
4. for a non uniform conductor,surface charge density varies inversely as radius of curvature.
3.MAGNETISM
1.when a current carrying wire lies in the plane to the right of the wire,the magnetic field is into the plane of the paper and towards the left of the loop,it is out of the plane of the paper.
2.in terms of length of magnetic field,the deviation of a charged particle is given by theta=sin^-1(x/r).here r is radius of circle traced by the particle and x is the length upto which the magnetic field exists.note that,this relation is valid only for x less than or equal to r since sine theta cannot be greater than 1.if x is greater than r,the deviation will be angle of a semicircle or "pi" radians.
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