OHM’S LAW
Electronics and
Instrumentations for Electro
neurophysiology
1.1
2.2
Objectives
3.
2.1
1.
2.2
Verification of Ohm's
law
Determination of the
equivalent resistance of
two resistors
Determine the equivalent
resistance in Series
Determine the equivalent
resistance in Parallel
Theory
OHM’S LAW
if a conductor is kept at a
constant temperature, then the
current passing through it is
directly proportional to the
potential difference between its
ends
OHM’S LAW
V = the potential difference across
the conductor, measured in
volts (V)
I = The current passing through the
conductor, measured in
amperes (A)
R = The proportionality constant,
called the resistance of the
conductor, and measured in
ohms (Ω).
5
Resistance in Series
When two resistances are connected as shown in Fig(1). they are said to
be connected in series.
In this case the
V= V1+ V2 = І R1+ І R 2
Or V= І R
Where
is called the equivalent resistance
Resistance in Parallel
When two resistors are connected as shown in Fig.(2) they are said to be
connected in parallel.
In this case the
And
So
V= І1 R1 = І2 R2
І = І1 + І2 = v/R1 + v/R2
І = v/R
Where
is called the equivalent resistance
Apparatus
Apparatus
Multi-meter (AVO meter)
Multi range voltmeter
Various resistances (conductors)
Ohmmeter
Power supply
Switch key (ON/OFF).
General
Procedure
1-Connect the circuit as shown in Figure .
2- Start with the minimum value of the input voltage, then record
the reading of both voltmeter and ammeter.
3- Change the voltage value, then record the new readings of the
ammeter.
4- Tabulate your results in the table.
5- Use a graph paper to plot a graph of V on y-axis versus I on x-axis.
6- Find the slope of the obtained line
7- Compare between Theoretical and experimental value of Requ.
Experimental
Data
Table 1
R1=
Ω
V (…….)
R2=
I (…….)
V (…….)
0.5
0.5
1
1
1.5
1.5
2
2
2.5
2.5
V (Volts)
Slope = 𝑹𝟏
Slope = 𝑹𝟐
I (mA.)
Ω
I (…….)
Table 2
Series
Parallel
R1=………(……)
R1=……….. (………),
R2=……..(……..)
R2=……….. (………)
V (…….)
I (…….)
V (…….)
0.5
0.5
1
1
1.5
1.5
2
2
2.5
2.5
V (volts)
Slope =R1+R2
I(mA)
I (…….)
Results
Calculation
Slope1 of (V/V) Vs (I/mA) graph1 = ...........…………………………………………………………………………………………
Comp - Requ. Th = ............................………………………………………………….Ω
Comp - Requ exp = ........................................................................................................... Ω
Percentage error % =……………………………………….%
THANKS
Do you have any questions?