SAI'S SCIENCE AND MATHS CLASSES

Short description on Magnetic effect (class IX) The magnetic effect of electric current was discovered by Hans Christian Oersted . The magnetic field strength ( B ) is determined by the strength of the current The magnetic strength decreases as we move away from the conductor The magnetic field lines (imaginary) created by a long conductors is in the form a concentric circle with the axis of conductor at the centre The direction of magnetic field in a current carrying wire can be determined by Right Hand Thumb rule or Cork Screw rule.  SI unit of Magnetic field is Tesla  other unit is Gauss .

Short description on Magnetic effect (class IX) The magnetic effect of electric current was discovered by Hans Christian Oersted . The magnetic field strength ( B ) is determined by the strength of the current The magnetic strength decreases as we move away from the conductor The magnetic field lines (imaginary) created by a long conductors is in the form a concentric circle with the axis of conductor at the centre The direction of magnetic field in a current carrying wire can be determined by Right Hand Thumb rule or Cork Screw rule.  SI unit of Magnetic field is Tesla  other unit is Gauss .

1) The power rating and voltage rating of a device are 600W, 200V Find a) current rating b) resistance offered by the device c) energy consumed in 1 hr Ans: a) Power =VI I=P/V= 3 A b) R=V/I= 200/3 ohm c) E=Power x time=600x60x60= 2160000 J 2) Two wires one of copper and other of Nichrome have same length and resistance Which wire will be thicker? Justify Ans: resistivity=Resistance x Area / length since length and resistance is the same for both the wires we can compare their area The Nichrome wire, since an alloy will be having more resistivity , will be thicker. 3) A 15 ohm resistance wire is cut in to 3 equal pieces and then connected in parallel across a 5V battery Find a) current through each wire b) effective resistance  Ans: resistance is directly proportional to length of the wire if it is cut in to 3 equal pieces resistance of each piece will be equal to 5 ohm effective resistance of parallel combination  (1/R)=(1/R 1 )+(1/R 2 )+(1/R 3 ) then R