Experiment no. 8

Maharashtra Institute of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Verification of Ohm’s Law.
EXPERIMENT NO.8 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1
FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electrical Engineering Location Part I Page 37
Aim: Verification of Ohm’s Law.
Apparatus:
1. 4 varied value of resistors 2.Power supply 3. Connecting wires 4.Multimeter
Theory :
The most basic quantities of electricity are voltage, current and resistance. Ohm's law shows a simple
relationship between these three quantities, hence this law can be considered as the most basic law of
electrical engineering. This simple, easiest to remember, three character law of electrical engineering
helps to calculate and analyse electrical quantities related to power, efficiency and impedance.
The statement of Ohm’s law is simple, and it says that whenever a potential difference or
voltage is applied across a resistor of a closed circuit, current starts flowing through it. This current is
directly proportional to the voltage applied if temperature and all other factors remain constant. Thus
we can mathematically express it as:
V ∝I
Now putting the constant of proportionality we get,
V=IR
This particular equation essentially presents the statement of this law where I is the current through
the resistor, measured in Ampere (Ampere, or amps), when the electric potential difference V is
applied across the resistor in unit of volt, and ohm(Ω) is the unit of measure for the resistance of the
resistor R.It’s important to note that the resistance R is the property of the conductor and theoretically
has no dependence on the voltage applied, or on the flow of current. The value of R changes only if the
conditions (like temperature, diameter length etc.) of the material are changed by any means.
Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable

Aurangabad
LABORATORY MANUAL
The applications of ohm’s law are that it helps us in determining either voltage, current or resistance
of a linear circuit when the other two quantities are known to us.
Apart from that, it makes power calculation a lot simpler, like when we know the value of the
resistance for a particular circuit, we need not know both the current and the voltage to calculate the
power dissipation since P = VI. Rather we can use Ohm’s Law
V=IR
I=
V
R
To replace either the voltage or current in the above expression to produce the result
P=VI=
V
2
R
=I
2
R
These are the applications of Ohm’s law as we can see from the results, that the rate of energy loss
varies with the square of the voltage or current. When we double the voltage applied to a circuit,
obeying Ohm’s law , the rate at which energy is supplied (or power) gets four times bigger. This
phenomena occurs because increasing the voltage also makes the current rise by the same amount as
it has been explained above.
Limitation of Ohm’s Law
The limitations of Ohm’s law are explained as follows:
1) This law cannot be applied to unilateral networks.
A unilateral network has unilateral elements like diode, transistors, etc., which do not have same
voltage current relation for both directions of current.

Aurangabad
LABORATORY MANUAL
2) Ohm’s law is also not applicable for non – linear elements.
Non – linear elements are those which do not give current through it, is not exactly proportional to
the voltage applied, that means the resistance value of those elements changes for different values of
voltage and current. Examples of non – linear elements are thyristor, electric arc, etc.
Procedure:
The experiment setup consists of a simple circuit with a variable resistance and simple power source,
which are 3 batteries (1.5 Volt each). The diagram beside shows the single circuit that we will use for
this experiment: Choose a Voltage range and then vary the value of the resistance over the range. As
expected from Ohm’s law, it will be seen the voltage range and value of the resistance chosen will be
linear and the value of resistance will be perpendicular to the current.
1. Set up the apparatus to be the circuit as shown in diagram of hypothesis.
2. Set the value of electromotive force into 3 V.
3. Put the 12-ohm resistor and see the value of current in the Multimeter.

Aurangabad
LABORATORY MANUAL
4. Change the 12-ohm resistor with 82 and 470-ohm resistor varied and repeat step 3.
5. Change the value of electromotive force into 6 V.
6. Repeat steps 3 and 4 (use 56-ohm resistor instead of 12-ohm resistor, because the value of 12-ohm
resistor is too small for 6V of electromotive force).
Observation Table:
Experiment In Calculation
Current Resistance Voltage V = IR
3 V
3 V
3 V
6 V
6 V
6 V
Conclusion: Write your own conclusion. From this experiment, we can see that the values of
voltages depend on how big are the values of resistors. The bigger the values of resistors, the bigger
the values of electromotive force will be resulted. This shows that the voltage range and resistor value
is linear to each other, while perpendicular with the value of current. For more clear details, see the
table of the experiment data above.

Experiment no. 8

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