[...] 20] A solenoid of length L = 24 cm, radius r1 = 140 cm, with 600 windings is traversed by a current i1 = 32.0 mA flowing from top to bottom in an anti-clockwise direction. A second solenoid, of equal length, radius r2 = 0.60 cm, and with 500 windings is inside the first solenoid, and the axes of the two coincide. The second solenoid is traversed by a current i2 = 21.0 mA, and its coils wind clockwise moving from bottom to top. Calculate the total magnetic field at points P and Q, which are distant dP = 0.40 cm and dQ = 1.20 cm from the axis of the two solenoids, when the current i2 flows in the second solenoid:

• from bottom to top.
• from top to bottom.

[4.0 x 10^-5 T; 1.0 x 10^-4 T; 1.6 x 10^-4 T; 1.0 x 10^-4 T]