Rev. Notes > IGCSE > Electric Circuits Previous Topic Electric Circuits Next Topic Topics
 Electric circuit Circuit symbols Circuit diagrams Diode Diode as forward biased and reversed biased Diode as a rectifier Diode as half wave rectifier Diod as full wave rectifier Transistors Series circuits Parallel circuits Effective or equivalent resistance in series circuits Effectice or equivalent resistance in parallel circuits Advantages of connecting lamps in parallel in lighting circuits Potential divider or Potentiometer Thermistors Light dependent resistor - (L.D.R.) Input transducers Capacitors Capacitance of the capacitor One Farad Different types of capacitors Time delay circuits Relay Rectifier circuits Transistor as switch Light sensitive switch Temperature operated alarms

## Diode as forward biased and reversed biased

Diode as forward biased: The semiconductor diode (PN-junction diode) has the tendency to allow the current to flow in one direction only from P-side to N-side (+ to -) through the PN-junction. When a battery is connectetd accross the PN-junction diode as shown in the figure below, with positive terminal of the battery connected to the P-type and negative terminal to the N-type of the diode. The diode is said to be forward biased a shown below..

The positive terminal of the battery repells holes accross the junction and attracts electrons crossing the junction. The negative terminal repells the electrons accross the junction and attracts holes crossing the junction. Thus giving rise to a large current which can be recorded using an ammeter in a circuit.

Diode as forward biased: If the polarity of the battery is reversed as shown in the figure below, holes and electrons do not cross the junction. Thus no current or a very little current flows through the circuit and the diode is said to be reverse biased.

-----------------------

-----------------------

 O,sidds Said : THERE SHOULD HAVE BEEN MORE DIAGRAMS!!! but the explanations are good. 12/01/15 10:30 PM

 skyler Said : you are missing diagrams! but helpful website! 02/05/13 03:18 AM

 Bareera Khizar Said : gr8!!! useful 4 last min revision nd especially 4 lazy lumps!! 14/04/13 09:13 PM

 Bareera Khizar Said : gr8!!! useful 4 last min revision nd especially 4 lazy lumps!! 14/04/13 09:13 PM

 PRIOCCUPIED Said : THANKS :) 14/10/12 06:53 PM

 Lakshey Said : Best site in all of those i founded on internet. 29/08/12 08:07 AM

 Thiago Said : This site is great, like the other comments say, its straight forward and to the point! Thx 12/06/12 03:02 AM

 Aubrey Graham Said : This website was really useful, it really did help me prepare for my physics IGCSE exam. Thank you so much, your website is structured in short, straight to the point information. One word brilliant.------------------------------------------------------------------------------------- Admin Replied: We are glad it helped you :) keep visiting and thanks for your feedback 22/05/12 03:23 PM

 Ghost Said : Thnak you sir, really helpful but some of the diagrams are missing, if u could post those too, it would be helpful... Safwan :) 16/05/12 02:24 PM

 Irshad Said : I found this website very useful for revision.------------------------------------------------------------------------------------- Admin Replied: Thank you :) 17/04/12 10:37 AM

 Princess Zoya Said : Wow this is great !! Thnx alot !! BTW i need explanation in detail for Hydroelectric powerstation !!------------------------------------------------------------------------------------- Admin Replied: Thank you :) We will make sure we provide further explaination regarding the topic u've mentioned. 10/04/12 03:36 PM

 Coop Cooper Said : This Is Great------------------------------------------------------------------------------------- Admin Replied: Thank you :) 28/03/12 10:04 PM