Article about Resistivity
Regarding electric current, the density of electric current has been discussed, so also the electric field has been explained in-topic about the electric field. The electric field and electric current are in a conductor if there is a potential difference in the conductor, whereas if there is no potential difference, then there is also no electric field and electric current.
In almost all metal conductors, the electric field is directly proportional to the density of the electric current, where the ratio of the electric field to the density of the electric current is constant. The value of the comparison of the electric field to current density is called resistivity. Mathematically, the relationship between the electric field, current density, and resistivity is stated in the equation:



Peraturan pertama Kirchhoff yang juga dikenali sebagai peraturan titik simpang menyatakan bahawa arus elektrik yang memasuki titik simpang adalah sama dengan arus elektrik yang keluar dari titik simpang tersebut. Titik simpang dalam litar elektrik ialah titik di mana dua atau lebih daripada dua konduktor bertemu, seperti titik a dalam rajah di sebelah.
Untuk lebih memahami perkara ini, bayangkan cas elektrik bergerak dalam litar tertutup, seperti dalam rajah. Apabila cas elektrik melalui