T.C.
MARMARA UNIVERSITY
FACULTY OF ARTS AND SCIENCES
PHYSICS DEPARTMENT
PHYSICS LABORATORY - II
DEPARTMENT:
NAME:
SURNAME:
NUMBER:
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T.C.MARMARA UNIVERSITY PHYSICS DEPARTMENT
PHYSICS LABORATORY –I I MANUAL
EXPERIMENT NO:
EXPERIMENT NAME:
THE DATE:
GROUP NO:
NAME:
NUMBER:
DELIVERY TIME:
REPORT NOTE:
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EXPERIMENT.3
NON-OHMIC DEVICES IN A CIRCUIT-1
Goal:1.) Investigation of current-voltage characteristic of non-ohmic devices in a circuit
Theory: Resistance of non-ohmic devices is not constant and it changes with as a function of
current. For example, in one of the non-ohmic devices, filament bulbs, if we rise current, it
emit more light and wire in the bulb gets hot. If we draw current-voltage graphic of these
devices, we observe a non-linear character.
Similarly, dynamic resistance value of this filament
is represented by dV/dI. Current-voltage
characteristic of another non-ohmic devices,
diode, is shown right side and its dynamic
resistance is:
rd 
VD
I D
Static resistance is obtained from specific current
that correspond specific DC voltage for static
resistance. It is a dynamic resistance that observed
around forward voltage point.
Current passes in organic diodes and LED’s only
one way. They may show high or low resistance
depending on polarity of applied voltage. LED’s
are conductor for forward voltage and they can
conduct very small current(~mA) for reverse
voltage. –This small current is known as
‘leakage current’.- LED’s emit light with only
forward voltage.
Filament bulb is getting hot while current is passing on it so it must be observed that
resistance is how depends on temperature. Resistance of bulb is changing with temperature
as formula given below. α is temperature coefficient for tungsten.
R=Rroom[1+α(T-Troom)]
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Experimental Setup:
Apparatus:
1.)Board
2.)Filament bulb
3.)DC voltage source
4.)Digital multimeter
5.)Connectors
EXPERIMENTAL SETUP AND MEASUREMENTS:
1.) Build the circuit shown figure above.
2.) Connect a small resistance on the branch that connected to bulb. This prevent heating and
burning of the bulb.
3.) Apply max. 6 V DC from power source to circuit and increase the voltage step by step.
4.) Write the values that you read amperemeter and voltmeter that connected to resistance
and bulb to the table.
Voltage(VR)
Voltage(VB)
Current(A)
5.) Draw I-V graphics for voltage and current values you read on resistance and bulb.
Calculate static resistance via slope of the graphic you get.
6.) Calculate resistance of bulb for maximum voltage.
7.) Calculate power of bulb for the maximum voltage.(P=V2/R)
8.) Calculate resistance of bulb at room temperature using the graphic you drew for
bulb.(Find resistance from the point that intersect graphic minimum voltage and current
scala.)
9.) Record the temperature of your laboratory.
10.) Calculate temperature coefficient for tungsten wire using resistance value you found for
maximum voltage. You can use resistance-temperature formula.
Note: Temperature coefficient for tungsten is 4.5 10-3 K-1 .
11.) Calculate your percentage error for temperature coefficient you found.
12.) Interpret your conclusions.
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EXPERIMENT.3 NON-OHMIC DEVICES IN A CIRCUIT-1-NOTES:
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