\begin{align*} e &= 1.602 \cdot 10^{-19}~\rm C \\ Q &= n \cdot e \end{align*}
with $n \in \mathbb{Z}$.
\begin{align*} [Q] = 1~\rm C = 1~A \cdot s \end{align*}
How many electrons correspond to a charge of $1~\rm C$? \begin{align*} n = \frac{Q}{e} = \frac{1~\rm C}{1.602\cdot 10^{-19}~\rm C} \approx 6.24 \cdot 10^{18} \end{align*}
An electric current arises when charges move in a preferred direction, e.g. by attraction and repulsion. The current is defined as
\begin{align*} I = \frac{Q}{t} \end{align*}
The instantaneous current is defined as
\begin{align*} i(t) = \frac{{\rm d}Q}{{\rm d}t} \end{align*}
Unit check:
\begin{align*} [i] &= \frac{[Q]}{[t]} = \frac{1~\rm C}{1~\rm s} = 1~\rm A \end{align*}
Charge transport can take place through
An electrode is a connection (or pin) of an electrical component.
Looking at a component, the electrode is characterized as the homogenous part of the component, where the charges come in / move out (usually made out of metal).
The name of the electrode is given as follows:
As a mnemonic, you can remember the diode's structure, shape, and electrodes (see Abbildung 2).
Every rock on a mountain has a higher energy potential than a rock in the valley. As higher up and as more mass the rock has, as more energy is stored. The energy difference $\Delta W_{1,2}$ is given by the height difference $\Delta h_{1,2}$
\begin{align*} \Delta W_{1,2} = m \cdot g \cdot \Delta h_{1,2} \end{align*}
Similarily, charges on the positive pin of a battery has a higher energy potential than charges on the negative pin. Similar to the transport of a mass in the gravitational field, energy is needed/released when charge is moved in an electric field. We will look at the specific electric field starting from block09.
For the energy in an electric field, as higher the object is charged ($Q$), as more energy $\Delta W_{1,2}$ can be released / is needed for movements. The equivalent to the height $h$ in the mechanic picture is the potential $\varphi$ in the electric case:
\begin{align*} \Delta W_{1,2} = Q \cdot \Delta \varphi_{1,2} \end{align*}
It follows that:
\begin{align*}
\boxed{{\Delta W_{1,2} \over {Q}} = \varphi_1 - \varphi_2 = U_{1,2}}
\end{align*}
voltage $U_{1,2}$ is the energy $W_{1,2}$ per charge $Q$ between two points $1$ and $2$.
1V8
and 5V0
or in general as VCC
or VDD
)
A charge $Q=2.0~{\rm mC}$ moves through a potential difference of $5.0~{\rm V}$. Energy transferred:
$W=U \cdot Q=5.0~{\rm V} \cdot 2.0~{\rm mC}=10.0~{\rm mJ}$.
Potential Energy
Potential energy is always related to a reference level (reference height). The energy required to move $m$ from $h_1$ to $h_2$ is independent of the reference level.
$\Delta W_{1,2} = W_1 - W_2 = m \cdot g \cdot h_1 - m \cdot g \cdot h_2 = m \cdot g \cdot (h_1 - h_2)$
Potential
The potential $\varphi$ is always specified relative to a reference point.
Common used are:
To shift the charge, the potential difference must be overcome. The potential difference is independent of the reference potential. $\boxed{\Delta W_{1,2} = W_1 - W_2 = Q \cdot \varphi_1 - Q \cdot \varphi_2 = Q \cdot (\varphi_1 - \varphi_2)}$
A balloon has a charge of $Q=7~{\rm nC}$ on its surface.
How many additional electrons are on the balloon?
To get a different metal coating onto a surface, often Electroplating is used. In this process, the surface is located in a liquid, which contains metal ions of the coating.
In the following, a copper coating (e.g. for corrosion resistance) shall be looked on.
The charge of one copper ion is around $1.6022 \cdot 10^{-19}~{\rm C}$, what is the charge on the surface if there are $8 \cdot 10^{22}~{\rm ions}$ added?
\begin{align*} 8 * 10^{22} \cdot 1.6022 *10^{-19}~{\rm C} = 12'817.6~{\rm C} \end{align*}
Explain whether the voltages $U_{\rm Batt}$, $U_{12}$ and $U_{21}$ in Abbildung 5 are positive or negative according to the voltage definition.
+
is the higher potential. Terminal 1 has the higher potential. $\varphi_1 > \varphi_2$
A flashlight bulb is supplied with $I=0.25~\rm A$. How many electrons pass through the filament in one second?
How many electrons pass through a control cross-section of a metallic conductor when the current of $40~{\rm mA}$ flows for $4.5~{\rm s}$?
\begin{align*} Q &= I \cdot t \\ &= 0.04~{\rm A} \cdot 4.5~{\rm s} \\ &= 0.18~{\rm As} \\ &= 0.18~{\rm C} \\ &={0.18~{\rm C}}\cdot {1\over{1.6022*10^{-19}{\rm C/electron}}} = 1.1 \cdot10^{18}~{\rm electrons} \end{align*}
Two objects experience a charge increase per time. In the Abbildung 6 one can see these increases in the charge per time.
1. Determine the currents $I_1$ and $I_2$ for the two objects from the $Q$-$t$-diagram Abbildung 6 and plot the currents into a new diagram.
2. How can the current be determined, when the charge increase on an object changes non-linearly?
Charge in Matter
What is Electric Charge and How Electricity Works
Electric - Hydraulic Analogy: Charge, Voltage, and Current