The drift speed in a copper wire is 7.89 ✕ 10−5 m/s for a typical electron current. calculate the magnitude of the electric field e inside the copper wire. the mobility of mobile electrons in copper is 4.5 ✕ 10−3 (m/s)/(n/c). (note that though the electric field in the wire is very small, it is adequate to push a sizable electron current through the copper wire.)

 = 0.0175 N/C

Explanation:

= drift speed in a copper wire = 7.89 x 10⁻⁵ m/s

μ = mobility of mobile electrons in copper wire = 4.5 x 10⁻³ (m/s)/(N/C)

= magnitude of electric field in the wire

Drift speed is given as

= μ

Inserting the values

7.89 x 10⁻⁵ = (4.5 x 10⁻³)

 = 0.0175 N/C

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.