Question

For many technical applications, it is desirable to have a uniform magnetic field, i.e. a field with the same strength and direction at every point in a certain region of space. As you discovered in the last checkpoint, this can be achieved with a solenoid, which is constructed by "stacking" many loops of wire, each with the same current. The superposition of the magnetic fields of the single loops creates a strong, nearly uniform field inside the solenoid, whereas the field on the outside is weak and is approximately zero. 4 The magnetic field near the centre of an ideal solenoid is given by B = Honl, where Ho = 41 x 10-7 T-m/A is the magnetic constant, I is the current that runs through the solenoid, and n = N/L is the number of turns per unit length. Note that the magnetic field does not depend on the radius of the solenoid. Question 7: You are given a solenoid with n = 100 turns per meter and are asked to generate a magnetic field inside the solenoid that is large enough to cancel the magnetic field of the earth, the average value of which is 5 x 10-5 T on the surface of the earth. How big does the current have to be? Question 8: If you want this current to be as small as possible (for the magnetic field given in the previous question), should the solenoid be stretched or compressed? Answer this question by finding an algebraic expression for I in terms of n first, and then write your explanation.

Answer 1

7 n I and carrying L and n will decrease. som let consider a Solenoid of Length L, number of turn/ length an > B. current I The magnetic field îmide it n = loo tuom/m. B = Monr B=58io-s. I = Mon 0 I = 44X10-7 X100 B =0.8ł Ang I = 2.513 Amp From equation 0 Ian when Lis Large i when Solenoid is stretched. 5X1o-s. some one rotation. Sola, for given figure from point "0" to point "1" it complete, only figure it appears there N=12 turns in Span of length 20cm. - N n=60 Turn/ meter Soin 10 10 from Number of tumpleng n=N with