IIT JEE , AIEEE Forum - Physics , General

harsha_27

1.FERMI'S THEOREM .......if a body is acted upon by three forces and is in equilibrium.....then F1/SinA = F2/SinB = F3/ SinC where A is angle b/w F2 AND f3 ,B is the angle b/w F1 and F3 and C is the angle b/w F1 and F2
2.+I effect is very small compared to -I effect.....if in a molecule two effects are present then -I effect dominates +I effect.
3.DELTA STAR TRANSFORMATION IN RESISTORS (NOT IN IIT SYLLABUS BUT THIS SHORT CUT METHOD SAVES TIME)......
if in any circuit if three resistors R_a , R_b , R_c are connected in a triangular order as shown in figure ....we can always replace them with equivalent resistances R₁ ,R₂, R₃ so that equivalent resistance b/w the points N₁ ,N₂ , N₃ is unaltered......this is a very easy and time saving method to find out equivalent resistance in large circuits by converting the triangles to delta forms and hence simplifying the circuit..here R₁ =R_a R_b/R_a+R_b+R_c ,R₂ = R_b R_c/ R_a+R_b+R_c,R ₃=Ra R_c/R_a+R_b+R_c

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