Physics-
General
Easy
Question
Two long parallel conductors carry currents in opposite directions as shown. One conductor carries a current of 10 A and the distance between the wires is d=10cm Current I is adjusted, so that the magnetic field at P is zero. P is at a distance of 5 cm to the right of the 10 A current. Value of I is
- 40 A
- 30 A
- 20 A
- 10 A
The correct answer is: 30 A
From Biot-Savart’s law the magnetic field 
due to a conductor carrying current 
at a distance 
is
Magnetic field at 
due to current in second conductor is
From Fleming’s right hands rule the fields at are directed opposite.
Given, 
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