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™ Activity
1
qoidentify a diode, anLED, a regi,
ais:
Apparatus. Multimeter,
Material, Above mixed collection of items,
qHEORY
For identification, 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. ALED (light. emitting diode) is also atwo-terminal device, Ttalso conducts ‘when forward
biased and does not conduct when reverse biased. It emits light while conducting. Hence,
it glows,
3. Aresistor is a two-terminal device. It conducts when either forward biased or Teverse
biased. (Infact there is no forward Or reverse bias for a resistor). It conducts even when,
operated with A.C. voltage,
: .
1000 uF
“eV
—
Paper Electrolytic
(b) Capacitors
(c) Diodes ee
ircuit elements.
Fig. Some of the commonly available circuit e
181
b> , ™
- Camprehensire Matical Pliysee yy
PROCEDURE
If the item has two terminals, it may be diode, a LED, a resistor or a capacitor,
In order to differentiate proceed as ahead:
Connect the battery eliminator, reversing key, the items to be Identified and the nuttiinetey
Switch on the circuit and carefully observe the movement of the pointer of the multinetey
If pointer moves when voltage is applied in one way and does not move when reversed arf
isa diode,
there is no light emission, the ite
If pointer moves when voltage is applied in one way and does not move when reversed 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 Hom ina
resistor.
If pointer does not move when voltage is applied in one way and also when reversed, the
item is a capacitor.
OBSERVATIONS
No. of | Number oflegs Name of device Possible current | Name ofdevice |
Obs. | flow
1 Two " Capacitor, Diode, Unidirectional, a
| jue or resistor emits no light
| | 3. | Unidirectional, LED
| | emits light |
| Both directions Resistor |
(steady)
5. Initially high but Capacitor |
decays to zero
To use a multimeter to (a) identify base of a multimeter (b) distinguish between non and pop type transistors (c) see the unidirectional flow of current in case of a diode and an LED (d) check whether a given electronic component (ex- diode, transistor, or IC) is in working order
