일반물리학 2 — Magnetic Fields Due to Currents: Problem 43

43 A student makes a short electromagnet by winding 280 turns of wire around a wooden cylinder of diameter \( d = 5.0 \text{ cm} \). The coil is connected to a battery producing a current of \( 3.8 \text{ A} \) in the wire. (a) What is the magnitude of the magnetic dipole moment of this device? (b) At what axial distance \( z \gg d \) will the magnetic field have the magnitude \( 5.0 \text{ \mu T} \) (approximately one-tenth that of Earth’s magnetic field)?