help gt mockssss!!!!! - PHYSICS

[Naruto123]

can any1 help me understand wat transistors diodes relay switches? do plzzzzzzzzzzzzzzzzz
urgent!!!!!!!!

[@d!_†oX!©]

hmmm...kk...

Diodes
A diode is a semiconductor device which allows current to flow through it in only one direction. Although a transistor is also a semiconductor device, it does not operate the way a diode does. A diode is specifically made to allow current to flow through it in only one direction.
Some ways in which the diode can be used are listed here.
 A diode can be used as a rectifier that converts AC (Alternating Current) to DC (Direct Current) for a power supply device.
 Diodes can be used to separate the signal from radio frequencies.
 Diodes can be used as an on/off switch that controls current.
This symbol (attached) is used to indicate a diode in a circuit diagram.

Relay Switches
A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and they are double throw (changeover) switches.

Relays allow one circuit to switch a second circuit which can be completely separate from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits, the link is magnetic and mechanical.
see the animated pic attached

Transistors
Transistors amplify current, for example they can be used to amplify the small output current from a logic IC so that it can operate a lamp, relay or other high current device. In many circuits a resistor is used to convert the changing current to a changing voltage, so the transistor is being used to amplify voltage.

A transistor may be used as a switch (either fully on with maximum current, or fully off with no current) and as an amplifier (always partly on).

The amount of current amplification is called the current gain, symbol h_FE.

If you need more info on the above try the ink below...
http://www.kpsec.freeuk.com/components/relay.htm    (just click on the links at the top oof the page to navigate to these topics)
and if u need more help or specific notes...tell me and i will be very happy to help ya...

[@d!_†oX!©]

hey By the way i haven't really explained the working cuz u just asked what do they do and not how they work....tell me if u want to know that too

[Ghost Of Highbury]

https://studentforums.biz/index.php/topic,4723.60.html

check the last post

cooldude has explained transistors beautifully!!

[Naruto123]

hey  thx a lot
i am gettin it nw  bt can u xplain hw transistor can be used as a switch i keep reading about a small circuit used to switch on another circuit  and one lamp gets on and de oder duznt hw r we suppose to knw wich1 duz ??
http://www.kpsec.freeuk.com/images/trtest2.gif
in this diagram wats ov ?
To test a PNP transistor use the same circuit but reverse the LED and the supply voltage.
wat duz this line above  mean ?