Tasheika Richards 6AS
EXPERIMENT: 4
SKILL: Planning and Designing
TOPIC: IV characteristics/ Resistance
AIM: To determine the IV characteristics of filament lamp
HYPOTHESIS: The resistance of the filament lamp will increase as the voltage increases and as
more current flows through the lamp the temperature of the filament will also increases
APPARATUS AND MATERIALS: Filament lamp, Power supply, ammeter and voltmeter,
connecting wire or leads, variable resistor.
DIAGRAM:
Title: DIAGRAM SHOWING THE FILAMENT BULB IN PARALLEL ACROSS THE
VOLTMETER AND THE VARIABLE RESISTOR IN PARALLEL WITH THE
FILAMENT LAMP AND THE AMMETER IN SERIES WITH THE
FILAMENT LAMP
VARIABLES:
DEPENDENT VARIABLE:
The temperature of the filament lamp for different potential difference. The units for
temperature will be Kelvins
The voltage that depends on the increasing resistance
Current of the filament
INDEPENDENT VARIABLE:
Tasheika Richards 6AS
The resistance of the power supply
CONTROL:
Length of lead
Power supply
METHOD:
1. Ensure that you have your equipments properly checked before taking readings.
2. Using the apparatus above, connect the power supply or battery to the variable resistor on
the left or the right using a lead or connecting wire.
3. Connect it to the middle of the variable resistor and the filament lamp. If you add the
leads on both ends (right and left) of the variable resistor, there will not be any changes in
the resistance which will then result in no change in the current.
4. Connect the component (filament lamp) to the ammeter using three more leads then from
the ammeter to the power supply and then from the component to the voltmeter.
5. Ensure the variable resistor is adjusted so that the potential difference is zeroed before
starting to take readings.
6. Record the readings on the voltmeter and ammeter.
7. Use the variable resistor to increase the potential difference starting from 1.0V
8. Using the voltmeter and ammeter record the new readings.
9. Repeat steps 7-8, each time increasing the potential difference slightly using a 0.2
interval which would be 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, and 2.6.
10. Turn around the leads in the power supply to reverse the power supply connections and
repeat steps 6-10 but decrease the potential difference. This means that current is flowing
in the opposite direction through the circuit.
11. Ensure both the voltmeter and ammeter has negative values and both the ammeter and
voltmeter has positive values
Tasheika Richards 6AS
12. Make observation and record the potential difference and its corresponding current in the
table below.
13. Plot a graph of current against potential difference.
14. Ensure to turn off power supply when not in use to prevent harm.
EXPECTED RESULTS:
The more energy that is put into the bulb, the harder it is for the current to flow – the resistance
of the bulb increases. As the voltage increases, so does the temperature of the thin wire inside the
bulb which is the filament. The atoms will vibrate rapidly about their mean positions, thus the
movement of the electrons through the filament lamp becomes restricted, and thus the resistance
of the lamp increases.When current flows through the filament lamp , it gets hot because the electrons
in the current flowing through the components collides with the particles that makes up it up. The
current through the lamp is directly proportional to the potential difference due to the filament getting
hot which resulted in an increase resistance . The movement of the electrons throughout the filament
lamp is being restricted thus the resistance of the filament increases as a result of the atoms vibrating
rapidly. The atoms in the filament vibrate or collide more in high temperature. It is also
expected that the readings obtained in the table to plot the graph will show that the graph (which
will be a t-shaped graph) has a slight curve towards both ends of the graph, both positive and
negative end. This shows that resistances is in constant for the filament lamp and that it doesn’t
obeys ohm’s law. The graph flattens slightly at the end as a result of the potential difference
increasing across the filament lamp.
TREATMENT OF RESULTS:
Title: Table showing potential difference, V (volts) and current, I (amperes) obtained
Potential difference, V (Volts) Current, I (amperes)
1.0
2.0
3.0
4.0
Tasheika Richards 6AS
5.0
6.0
7.0
8.0
9.0
10.0
PRECAUTIONS:
Ensure while connecting the circuit the power supply are turned off at start.
Make sure that the current is not too high, which will cause the filament bulb to blow up and
that is not safe working.
LIMITATIONS:
fluctuating ammeter or voltmeter readings that could alter the results
Experimenter’s error the variables were not read properly
ASSUMPTIONS:
Resistance of the lamp increases as the voltage increases. So more current flows through the
lamp, the temperature of the filament lamp will increase.
The increased vibrations of the ions in the filament will cause the temperature to increase
making it harder for the electrons to get pass
