Its task is to oppose the movement of charges. It limits the current in a circuit by converting electricity into heat, essentially wasting energy. Without a resistor, current flows in the conductor like water from a fully open tap, whereas a high resistance acts as a partially open tap. A closed tap would be an infinite resistance.
European (IEC)
American (US)
$ P[W] = V ⋅ I = \dfrac{ \; V^2}{R} = I^2 ⋅ R $
It is important to consider the maximum power of a resistor when building a circuit. In general, the maximum power of a resistor is between 200-600 [mW], but there are higher power resistors, called wirewound resistors.
Resistors are characterized by both nominal value and tolerance. This is a percentage value that indicates the limits within which the manufacturer guarantees the resistance. In many cases even a 5% difference is not a problem, in other cases it is essential to use a component with an accuracy of 0.1%.
Yes, it is used, for example, when two traces would cross on a printed circuit board (PCB) and therefore a bridge, a jumper is needed. In addition, in case of repair, such a resistor can be soldered out to break the circuit and its solder points can be used for measurements. Otherwise it might be used as a fuse.
Its job is to store energy. It can be considered a tiny battery with very low internal resistance. For this reason, both charging and discharging can happen very quickly, unlike with ordinary batteries.
Non-polarized
Polarized
Symbol: C
Unit: Farad [F]
A higher capacity capacitor with a given current takes longer to charge, but it also takes longer to discharge, lasts longer. Even the highest capacity supercapacitors do not currently compare with lithium and sodium batteries in terms of energy density, so they will not be replaced in the near future.
As the voltage of a battery increases continuously during charging, so does the voltage of a capacitor, and the voltage to which the capacitor charges is equal to the ratio of the charge flowed through it to the capacitance. A current-limiting resistor is used in the circuit. The capacitor's operation can be modelled as a membrane that collects the charges in the wire. The discharge process is the same but in reverse.
$ V_C = \dfrac{1}{C} ⋅ \displaystyle\int_{0}^{t} I_C \, \,dt $
$ I_C = C⋅ \dfrac{dV_C}{dt} $
$ \tau = R ⋅ C $
If the time of charging is considered instantaneous, a capacitor behaves as an open circuit in the case of DC, in other words as an infinite resistance. Its current is zero as it terminates the charge flow.
By their nature, capacitors respond to voltage changes with a proportional change in current. In comparison, a coil responds to a change in current with voltage. If the current is constant, there is no voltage drop across the coil. However, if there is a change (for example, a switch-off or switch-on), the voltage of the coil will jump and this can even cause damage. Many devices are made up of coils, such as transformers, motors or relays.
Symbol: L
Unit: Henry [H]
The current flowing through the coil creates a magnetic field around the coil. The field strength gradually increases and then stops increasing at a certain point. A coil with a higher inductance can be made if the number of turns is larger. The inductance can be further increased by using an iron core.
Simply, its operation is the reverse of that of a capacitor. Instead of the coil's voltage, the current increases exponentially after switching on, with a sudden jump in voltage followed by a gradual decrease. Its behaviour can be modelled as a water mill whose rotation slowly adapts to the flow of water. At first there is a pressure difference between the two sides, which gradually decreases.
$ I_L = \dfrac{1}{L} ⋅ \displaystyle\int_{0}^{t} V_L \, \,dt $
$ V_L = L ⋅ \dfrac{dI_L}{dt} $
$ \tau = \dfrac{L}{R} $
If the time of charging is considered instantaneous, the coil behaves as a short-circuit, in other words a zero resistance in the circuit. Its voltage is zero, since there is no change in current. However, this is only an ideal case, in reality its resistance is not zero, but a specific value given in the data sheet.