diff --git a/docs/sph3u7.md b/docs/sph3u7.md index 2d0555c..4b215c9 100644 --- a/docs/sph3u7.md +++ b/docs/sph3u7.md @@ -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. + +(Source: Kognity) + +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).