Two long wires a and b, carrying equal currents of 10*0A, are placed parallel to each other with a separation of 4*00 cm between them as shown in figure. Find the magnetic field B at each of the points P,Q and R.

Explanation

Solution: The magnetic field at P due to the wire a has
magnitude
` B_1= (mu_0)i/2pi d = ((4 pi xx (10^-7) TmA^-1) xx 10A)/ 2 pi xx 2 xx (10^-2)m.`
` =1*00 xx (10^-4)T.`
Its direction will be perpendicular to the line shown and
will point downward in the figure.
The field at this point due to the other wire has magnitude
` B_2=(mu_0)i/2pi d =(4 pi xx (10^-7)(TmA^-1) xx 10A)/(2pi xx 6 xx (10^-2)m)`
` = 0*33 xx (10^-4) T`.
`Its direction will be the same as that of B_1. Thus, the`
resultant field will be `1*33 xx 10^-4` T also along the same `
direction.
Similarly, the resultant magnetic field at R will be
`(=1*33 xx 10^-4) T along the direction pointing upward in`
the figure.
The magnetic field at point Q due to the two wires will
have equal magnitudes but opposite directions and
hence the resultant field will be zero.