Activities

ACTIVITY 1
AIM: To identify aiode, an LED, a resistor and a capacitor from a mixed
collection ofsuch 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.
1 A diode is atwo-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.
ALED (ight emitting diode) is alsoa two-terminal device. It also conducts when
biased and does not conduct when reverse biased. It emits light while conducting.forward
Hence,
it glows.
3 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.
4 Acapacitor 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 identifed are shown in figure.
123 4

Wire 1000 uF
6V
0.47 uF
-Rings Paper
Electrolytic
(a) Carbon resistor
Mica
(b) Capacitors

LED

(c) Diodes
Fig. Some of the commonly available circuit elements.
204
Activities 205
PROCEDURE

1 Ifthe item has two terminals, it may be diode, a LED, a resistor or a capaitoL
In order to differentiate proceed as ahead:
Connect the battery eliminator, reversing key, the items to be identiled and the multimeter.
Switch on the circuit and carefully observe the movement of the pointer of the
multimeter.
lf 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 reversed
and
there is light emission, the item is a LED.
( ) lf pointer moves when voltage is applied in one way and also when
reversed, the item is a
resistor.
(iv) 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 ofdevice No. of Possible current Name of device
Obs. Obs. flow
1 Two Capacitor, Diode,
Unidirectional, Diode
LED or resistor emits no light
3 Unidirectional, LED
emits light
Both directions Resistor
(steady)
5 Initially high but Capacitor
decays to zero