^Circular ring
Circular ring
Magnetic field on the axis of a circular ring
To find field at C use r = R & r = x for far away point.
Magnetic field is maximum at centre of ring, it is
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*Average speed
*Average speed
Speed between two instants is called average. Mathematically it is measured as the total distance covered per unit time spent. It is scalar & always positive.
i.e. Average speed
- For a given time interval average velocity is single valued while average speed can have values depending upon path followed.
- Average velocity & average speed are equal only for motion along a straight line with no reversal.
- The average speed can never be – ve or zero while average velocity can be.
- If a particle travels distances x1 , x2 & x3 with speeds v1 , v2 & v3 during time intervals t1, t2 & t3 respectively, then its average speed is
If x1 = x2 = x3, then this relation becomes harmonic mean of individual speeds. 
Also if t1 = t2 = t3, then the average speed is be given by Arithmetic mean of individual speeds. 
^Point object
^Point object
An object is said to be a point object if it covers distance much greater than its size.
^Two cells in parallel
Two cells in parallel
I = I1 + I2
^A long horizontal fixed wire carries a current of 100 A. Directly above and parallel to it is another wire carrying a current of 20 A and weighing 0.04 N/m.
^A long horizontal fixed wire carries a current of 100 A. Directly above and parallel to it is another wire carrying a current of 20 A and weighing 0.04 N/m. The separation between the two wires so that the upper wire is just supported by the magnetic repulsion is
