To identify a diode, an LED, a transistor, an IC, a resistor and a capacitor from a mixed collection of such items
Physics Lab Manual NCERT Solutions Class 12 Physics Sample Papers
Aim
To identify a diode, an LED, a transistor, an IC, a resistor and a capacitor from a mixed collection of such items.
Apparatus and material
Apparatus:
Multimeter.
Material:
Above mixed collection of items.
Theory
For identification, appearance and working of each item will have to be considered.
- A diode is a two terminal device. It conducts when forward biased and does not conduct when reverse biased. It does not emit light while conducting. Hence, it does not glow.
- A LED (light emitting diode) is also a two terminal device. It also conducts when forward biased and does not conduct when reverse biased. It emits light while conducting. Hence, it glow.
- A transistor is a three terminal device. The terminals represent emitter (E), base (B) and collector (C).
- An IC (integrated circuit) is a multi-terminal device in form of a chip. [See figure (UM 3482 IC Tone Generator)]
- A resistor is a two terminal device. It conducts when either forward biased or reverse biased. (Infact there is no forward or reverse bias for a resistor). It conducts even when operated with A.C. voltage.
-
A capacitor is also a two terminal device. It does not conduct when either forward biased or reverse biased. When a capacitor is connected to a D.C. source, then multimeter shows full scale current initially but it decay to zero quickly. It is because that initially a capacitor draw a charge.
The components to be identified are shown in figure.
Procedure
- If the item has four or more terminals and has form of a chip, it is an IC (integrated circuit).
- If the item has three terminals, it is a transistor.
-
If the item has two terminals, it may be diode, a LED, a resistor or a capacitor.
To differentiate proceed as ahead. - Put the selector on resistance R of multimeter for checking the continuity. The probe metal ends are inserted in terminal marked on the multimeter as common and P (or + ve).
If such that the black one is in common and red probe is in P (or + ve). On touching the two ends of the device to the two other metal ends of probes.
- If pointer moves when voltage is applied in one way and does not move when reversed and there is no light emission, the item is a diode.
- If pointer moves when voltage is applied in one way and does not move when re-versed and there is light emission, the item is a LED.
- If pointer moves when voltage is applied in one way and also when reversed, the item is a resistor.
- If pointer does not move when voltage is applied in one way and also when reversed, the item is a capacitor.
Observations
Physics Lab Manual NCERT Solutions Class 12 Physics Sample Papers
