Download L3 Ohms_law

TITLE:
OBJECTIVE:
Ohm’s law
To verify Ohm’s law
EQUIPMENT:
Variable voltage d.c. power supply, switch, resistors, circuit board.
THEORY:
Ohm's Law states that the potential difference (e.m.f), V across a resistance, R is directly
proportional to the current, I flowing through the resistance at constant temperature. This
is mathematically expressed V = R.I Volts.
PROCEDURE:
Figure 1 Voltage and current measurement
A
Ammeter
Variable voltage
d.c. supply
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Voltmeter
V
R
Connect the circuit as shown in Figure 1.
Identify the Resistor provided using the resistor colour code and ohmmeter.
Set the d.c. supply voltage initially to zero volts.
Adjust the supply voltage so that the resistance draws a current of 1 mA.
Read the potential difference across the resistance R with a voltmeter.
Adjust the supply voltage so that the current increases in steps of 1mA up to 10mA and read
the p.d. for each current setting. Draw up a table of results In EXCEL as shown.
Plot voltage against current to verify voltage is directly proportional to current i.e a linear
graph.
From the graph determine the resistance R which is equal to the slope of the line.
Compare the measured result with the marked value and determine if the resistor is within
its ± 5% tolerance.
Repeat the experiment using a different resistor. Plot your results on the same graph.