Electronics

1. A DC voltmeter: must be connected in parallel with the battery => compare the battery on-load voltage with the battery off-load => Difference a certain value 

2. Hydrometer the specific gravity: checks teh charhe of a battery by measuring the density 

Electric current causes a magnetic field => clockwise or anti clockwise ( Depending o the direction of the current)

- out of the cnductor ==> point symbol

- into teh conductor ==> cross symbol  

===> teh field is strongest near the conductor and becomes weaker with increasing distance from teh conductor 

To increase the strength of a magnetic fiel, it is possible to use more than one winding => result is a coil => magnetic force can be varied by the number of windings

radiate from the north pole and flow back into the south pole => inside the permanent magnet, the magnetic flow is from the south pole to the north pole

vgl. Bild ==> By AC voltage must be positioned corresponding to the present current direction

electrical field

the electrical force per unit charge (moving electrical charges) => the area between the capacitor plates if the capacitor is charged

produced by electric currents

a cil is wounded around a iron core => the result: field strength increases

Iron have a very low magnetic resistance => can guide magnetic field lines extremely well => elementary magnets in the iron are alined when a voltage is supplied to the coil ===> About 5000 time stronger than one without an iron

Moving conductor in a Magentic Field => electrons inside the conductor become displaced to one side => the amount of the voltage depends on the speed of movement and strength of the magnetic field => move almost 90 degrees to the direction of the field

an induced voltage of zero

Is the change of magnetic flux over time => The induced voltage increases with the speed of the conductor => Must be an energy input to the conductor (mechanical movement) => the induced voltage occurs only while the conductor is moving

to oppose the change in magnetic flux which caused the current => When DC voltage is switched on or off, there is a rapid change of the magnetic flux in the coil=> Fehlstrom => works against itself

initially blocks the supply voltage after being being switched on. The resulting current is therefore zero => After a fraction of a second the self induced voltage becomes zero

a) the length of teh coil

b) teh number of windings => more windings a coil has, teh higher the inductivity

c) an increasing are also increases the inductivity 

continues change of the magnetic flux => the current is constantly delayed => a higher frequency yields a higher change of magnetic flux with time

===> In a coil supplied with an AC sinusoidal voltage there is a phase shift of 90 degrees between the current and zhe voltage 

a voltage is induced in a conductor that is subjected to a changing magnetic field

=> When a coil with an iron core is supplied with altering current, the iron core s also influenced by the change of the magnetic flux

=> flow im a plane perpendicular to the magentic field lines

=> unwanted because it consumes power and producex heat in the device 

20 V 

the electrical circuits of the coil are totally separated from the circuits of the armature control contacts ==> possible to switch high power with small currents for the relays coil

it is necessary to monitoring )voltage, current, RPM etc.) by instruments => moving coil meter to indicate these parameters => uses the electromagnetic effect of a current => As a result, the coil starts to turn

when the coil is connected to a voltage source, the current produces a magnetic field that magnetism the armature => two magnetic poles exist in the gap between the iron core and the armature = the two contacts change their position and switching occurs

The moving coil meter can also function as a ammeter => Resistors for measuring range extension must be connected in parallel to the instrument coil

a moving coil meter can also be used to measure => the instrument must be connected parallel to the load whose voltage has to be measured => the resistance of the voltmeter must be as high as possible

two electrically separated coils wounded around a common iron coil => primary coil: the coil connected to the supply voltage (AC) => Produce a changing magnetic field => This affects the secondary coil, where a voltage is induced

The transformed AC voltage is connected to a rectifier => Changes AC voltage in DC

transforms DC in AC => The polarity of the current changed approximately 800 times per second => This leads to a changing magnetic field

Gerät AC => DC = Transformer Reftifier 

Gerät DC => AC = Inverter 

refers to detect the presence of nearby object without any physical contact => uses an AC current to generate a small, electromagnetic signal emitted from the end face of the sensing head ==> The interaction between the altering electromagnetic field and the metallic conductors in front of the sensing head!

=> Wenn z.B. die Türen zugehen, stört this  bzw. reduction of the field => Diese Störung wird erkannt und das Signal wird weitergeben, dass die Türen zu sind 

When a conductor passes through a magnetic fiel an electrical current is generated

the field lines depend on the direction of current

When a conductor moves perpendicularly to a magnetic field, a voltage is induced in the conductor => This voltage occurs because the electrons inside the conductor become displaced to one => Amount of voltage: depends on speed of movement and strength of teh magnetic field

the change of the magnetic flux over time and the number of windings