Question

28.45- A solenoid that is 40.0 cm long and contains 400 circular coils 1.40 cm in diameter carries a 1.55 A current.

A. What is the magnetic field at the center of the solenoid, 0.900 cm from the coils?

B. Suppose we now stretch out the coils to make a very long wire carrying the same current as before. What is the magnetic field 0.900 cm from the wire?

c. Is the magnetic found in part B the same as you found in part A? Why or why not?

Answer 1

l = 40 cm = 0.4 m

N = 400

d = 1.40 cm = 0.014 m

I = 1.55A

n= N/l = 400/0.4 = 1000 turns/m

The magnetic field at the cebter of solenoid is

B = 1.95 X 10^-3 T

magnetic field at r= 0.9 cm = 0.009 m is given by

Area of coil

A = 1.54 X 10^-4 m²

B = 2.62 X 10^-5 T

b)The magnetic field due to a long straight wire is

B = 3.44 X 10^-6 T

C ) The magnetic field in part B is not same as part A, magnetic field due to the solenoid is more as the field is concentrated more along the axis in solenoid, however, magnetic field due to a long wire is equally distributed along every radial direction