eggy/eifueo
1
1
Fork 1
Code Issues 2 Pull Requests Releases Wiki Activity

phys: basic current stuffs

Browse Source
This commit is contained in:
eggy 2021-01-25 17:59:10 -05:00
parent 77b8ad474c
commit 83460dcf55
1 changed files with 19 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
docs/sph3u7.md
View File

@ -868,7 +868,7 @@ $$\lambda_n=\frac{n}{4}L$$
A **charge** is a scalar that allows a mass to experience force from an electromagnetic field, and it may only be positive or negative. It is both **quantised** — the smallest charge possible is the one on a single proton/electron and all charges are multiples of that value — and **conserved** in a closed system.
Charges are expressed in **Coulombs** ($\text{C}$) with the symbol $q$. One electron has a charge of $1.60×10^{-19}\text{ C}$.
Charges are expressed in **Coulombs** ($\text{C}$) with the symbol $q$. One electron has a charge of $-1.60×10^{-19}\text{ C}$.
Similar to gravitation, the forces between charges is proportional to their charges and inversely proportional to the square of the distance between them.
$$F_E \propto q_1q_2 \propto \frac{1}{r^2}$$
@ -930,6 +930,24 @@ where any deltas refer to differences between the two plates.
As the electric field strength is constant, the equipotential lines in the field are also evenly distributed.
## 5.2 - Heating effect of electric currents
!!! definition
A **charge carrier** is any mass that enables charges to be moved over a potential difference.
Electric currents ($I$) are the flow of electrons due to a potential difference between both ends of a conductor. They are measured in **amperes** ($\text{A}$) which represent coulombs per second ($1\text{ A}=\frac{1\text{ C}}{1\text{ s}}$).
$$I=\frac{q}{t}$$
The **drift velocity** is the average velocity of electrons in a given volume.
<img src="/resources/images/drift-velocity.png" width=700>(Source: Kognity)</img>
As such, where $I$ is the current, $n$ is the number of electrons, $A$ is the cross-sectional area of the conductor, $q$ is the charge of one electron, and $v$ is the electron drift velocity:
$$I=nAvq$$
$$\Delta Q = nAv\Delta tq$$
In an electric circuit, electrons flow from the negative terminal to the positive terminal — however historically current was described as from the positive to the negative terminal and so that is known as **conventional current**, opposite the direction of electron flow.
## 6.1 - Circular motion
Circular motion is any motion along a circular path. The instantaneous velocity of an object in circular motion at any point is always tangent to its point on the circle, so the difference between any two velocities ($\Delta \vec{v}$) is radial (lies along the radius).