ABSTRACT
A straight conductor carries a current of 100 A. What is the magnetic field intensity at a distance of 25 cm from the center of the conductor?
In the MKS system, r 0.25 m. Using Eq. (1.3.3), B 100 A 4π 107 N/A2/(2π 0.25 m) 8 105 T
For a closed path in a magnetic field, the total flux φ is found by integrating the incremental surface area dA times the normal component of the magnetic field intensity B over any surface within the closed path:
φ B ⋅ dA (1.4.1) where
φ flux, Wb dA incremental surface area, m2
If the total flux is changing over time, there is an induced voltage E around the closed path surrounding φ. The value E in volts is equal to dφ/ dt, where the direction of E is in the right-hand sense. Figure 1.2 illustrates this principle of magnetic induction. If the magnitude of B is decreasing, then dφ/dt will be in the downward direction, and E will be in the positive in the right-hand sense around the closed loop that encircles φ.
