Originally posted by Miss.Mars
1. I am unable to decide how to find direction in case of Right hand thumb rule in magnetic induction/force/field. There are other rules too i know but our sir told to follow only the right hand rule so bit confused.
Right hand thumb rule basically says that when you curl fingers of your right hand and keep thumb up, then if your thumb is pointing in the direction of current, then the direction of your finger shows the direction of magnetic field. Like this,
You see, thumbs point up i.e. the direction of current, so direction of magnetic field is the direction of fingers i.e. anti clockwise.
There is another cool application of your right hand. You must have read cross product of vectors. E.g. - Force on a moving conductor in magnetic field is given by F=IL X B. Now, to know the direction of F, you can use the right hand rule. First stretch your right palm with the fingers pointing towards the direction of first vector, in this case I. Then curl your fingers towards the direction of second vector, in this case B. Then the direction of thumb will give you the direction of the resultant vector, in this case F. Remember, you may have to bend your hand in awkward positions to be able to curl from first vector to second, but it will always give correct result. Try it!
Originally posted by Miss.Mars
2. I am confused where to apply the wheatstone bridge principle and where not to? Totally confused about current distribution.
Wheatstone consists of four resistances. A pair of resistances is created by joining two in series. And now both series are connected in parallel. And then the mid point of the two series, where the two resistances of the series meet, are joined. This mid wire should not get any current when Wheatstone is balanced. E.g. you have four Resistance R1, R2, R3, R4. You connect R1, R2 in series and then R3,R4 in series. Now you connect both series in parallel. And the mid point i.e. where R1, R2 met and where R3, R4 met is joined and should not get any current.
The formula you get is R1/R3=R2/R4. If the arrangement of resistances is like Wheatstone and you know the value of all the resistances, apply the formula above. If it is true, then it is a Wheatstone and no current will pass through the mid wire. If you are told to find the value of unknown resistance, put the value of rest 3 and calculate the 4th.
Originally posted by Miss.Mars
3.I dont get head or tail of rotational kinematics.
I am sorry but it is not possible to explain the whole rotational kinematics here.
Edited by Freethinker112 - 30 July 2012 at 9:19am