Isra University
Practical # 01
Subject: Basic Electronics
Department: Electrical Engineering
Semester: 2nd
Batch: Fall 2012
Student’s Name:
ID: 1210-BE (EE)-
Date: 13-08-2013
Grade & Sig:
Title: Diode and its terminal identification.
Objective: Objective of this practical is to learn about diode and identify its terminals.
Required Apparatus:- Few diodes, breadboard, multimeter, connecting wire etc.
Theory:- Diode is a two terminal semiconductor device with ability to conduct current only
in one direction after a certain amount of voltage called barrier potential is applied to it in a
proper way. Diode is one of great invention which is used in many applications such as
rectifier circuits, voltage limiter circuits, voltage clamper circuits, voltage multiplier circuits
etc.
Procedure:- In this practical three methods are discussed below to identify diode terminals.
 Method 01: Physical shape
Diode is marked with a color band on one of its two sides and that colored side identifies
negative terminal (cathode) of a diode. For some other models, physical shape of a diode also
represents its terminals as shown in figure 01. Where K represents cathode or negative
terminal of a diode and A represents anode or positive terminal of diode
 Method 02: Using multimeter (Ohm meter)
When diode is connected with ohm meter and (i) if internal resistance of diode is in the range
of kilo ohms, then the terminal of diode which is connected with the positive of ohm meter is
called anode and other terminal will be called cathode. (ii) if internal resistance of diode is in
the range of mega ohms, then the terminal of diode which is connected with the positive of
ohm meter is called cathode and other terminal will be called anode.
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Figure 01: Different diode models are their terminal identification with the help of their
physical shape
 Method 03: Using diode option on multimeter
For checking a diode, most of the present day multimeters have diode option. After selecting
diode option on multimeter and attaching multimeter leads with diode; diode can be checked
as follows:
(i) if multimeter shows 0.7 volt (around barrier potential of diode) as shown in figure 02(a),
then the terminal of diode which is connected with positive of multimeter is called anode and
other terminal will be called cathode.
(ii) if multimeter shows 2.6 volt (around battery voltage of multimeter) as shown in figure
02(b), then the terminal of diode which is connected with positive of multimeter is called
cathode and other terminal will be called anode.
Figure 02: Checking diode terminals with the help of multimeter diode option
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Observation:- It is observed that when positive of diode is connected with positive of
multimeter, then multimeter showed 148.3 K ohm and when negative of diode is connected
with positive of multimeter, then multimeter showed 3.1 M ohm.
Answer the following questions:Question 01: What is a diode?
Question 02: How to identify different terminals of a diode using ohm meter?
Question 02: How to identify different terminals of a diode using diode option on
multimeter?
Question 03: What is the internal resistance of a diode when positive terminal of a diode is
connected with positive of ohm meter?
Question 04: What is the internal resistance of a diode when positive terminal of a diode is
connected with negative of ohm meter?
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD