To Identify A Diode, Led, A Transistor, An IC, Resistor And Capacitor From Collection Of Such Items - Practice Questions & MCQ

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 a mixed collection of items.

Theory-

For identification, the appearance and working of each item will have to be considered.
1. 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.
2. 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 glows.
3. A transistor is a three-terminal device. The terminals represent emitter (E), base (B) and collector (C).

4. An IC (integrated circuit) is a multi-terminal device in the form of a chip.  
5. A resistor is a two-terminal device. It conducts when either forward biased or reverse biased. (In fact there is no forward or reverse bias for a resistor). It conducts even when operated with A.C. voltage.
6. 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 decays to zero quickly. It is because initially a capacitor draw a charge.

Procedure-
1. If the item has four or more terminals and has the form of a chip, it is an IC (integrated circuit).
2. If the item has three terminals, it is a transistor.
3. If the item has two terminals, it may be a diode, an LED, a resistor or a capacitor.
To differentiate proceed as ahead.
4. 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.

1. If the 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.
2. If the pointer moves when voltage is applied in one way and does not move when reversed and there is light emission, the item is an LED.
3. If pointer moves when voltage is applied in one way and also when reversed, the item is a resistor.
4. If the pointer does not move when voltage is applied in one way and also when reversed, the item is a capacitor.

Result:

A diode, an LED, IC, resistor or capacitor can be identified.