Two parallel, long wires carry currents 
and 
with 
. When the currents are in the same direction, the magnetic field at a point midway between the wires is 10 μ μ T. If the direction of 
is reversed, the field becomes 30 μ μ T. The ratio 
is
Text Solution
Verified by ExpertsThe correct answer is:
C
Initially when wires carry currents in the same direction as shown. Magnetic field at mid point O due to wires 1 and 2 are respectively
and 
◉ ◉
Hence net magnetic field at O 
⇒ ⇒ 
.....(i)
If the direction of i 2 is reversed then
and 
So 
⇒ ⇒ 
......(ii)
Dividing equation (ii) by (i)
⇒ ⇒ 
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