AIM: To identify a diode, an LED, a resistor and a capacitor from a
mixed
collection of such items.
APPARATUS AND MATERIAL REQUIRED: A multimeter, a mixed
collection of diode, LED, resistor and capacitor.
THEORY:
DIODE. A two terminal device which conducts current when forward biased
and not when reverse biased. It does not emit light during its conduction.
LED. A light emitting diode is a two terminal device which conducts current
when forward biased and not when reverse biased. It emits light during its
conduction.
RESISTOR. A two terminal device which conducts equally in both directions.
CAPACITOR. A two terminal device which offers infinite resistance to dc but
has a finite reactance for ac. When connected across a dc source, a multimeter
shows a large current initially (for C>µF) which decreases to zero quickly. This is
because the capacitor initially draws a charge.
PROCEDURE:
1. Look for the color bands on the given components. If a component has a set
of three color bands followed by a silver or gold band, then the component is a
resistor.
2. Insert the black and red leads (or probes) into common and position
terminals of the multimeter. Turn its selector switch to resistance mode –
highest range (0-MΩ).
3. Touch the two probes to the two ends of each component one by one. Note
the direction of deflection in the multimeter. Interchange the position of two
probes for each component and again note the direction of deflection.
4. If the multimeter shows an equal deflection in both directions, then the
component is a resistor.
5. If the multimeter shows deflection in one direction without any emission of
light from the component and no deflection in the opposite direction, the
component is a diode.
6. If the multimeter shows deflection in direction along with the emission of
light from the component and no deflection in the opposite direction, then the
component is an LED.
7. If the multimeter does not shows any deflection on connecting its probes
either way to a component, then the component is a capacitor. But if the
capacitance of the capacitance is large deflection initially which gradually
decreases to zero.
8. Record all your observation in a tabular
RESULT:
From the mixed grouping of components, the components marked A,B,C and D
have been identified as resistor, diode, LED and capacitor respectively.
PRECAUTIONS:
1. While checking the conduction state of any component, clean its leads
properly.
2. Use the selector switch of the multimeter in resistance mode with highest
range option.
3. While testing any component, avoid touching the metal end of either of
multimeter probe.
OBSERVATIONS:
Table B1: State of conduction of each component
Item State of conduction of a component Identified component
code
A Conducts equally in both directions
Conducts in one direction without emission
B
of light
C Conducts in one direction with emission of
light
D
Does not conduct, gives an initial deflection
which decays to zero
