Material:
- Bulb (6V, 0.05A)
- Power supply
- Voltmeter
- Ammeter
- Wires
- Clamps
Variables:
Dependant variables: current
Independent variables: voltage
Controlled variables: Bulb, ammeter, voltmeter, power supply, wires.
Method:
- A wire was connected from power supply to the (mA) outlet of ammeter.
- A second wire was connected from the (com) outlet of ammeter to the bulb.
- A third wire was connected from power supply to bulb.
- Two wires connected from bulb to voltmeter in parallel. One wire to the (v) outlet of the voltmeter and one to the (com) outlet.
- The power supply was then turned on and the current in the ammeter was read at different voltage values which were set by adjusting the knob on the power supply equipment.
- Values were noted down right until the bulb was destroyed.
Result:
Calculation 1: R = V/I
- R = 0.0736
- R = 0.0990
- R = 0.120
- R = 0.135
- R = 0.148
- R = 0.161
- R = 0.172
- R = 0.183
- R = 0.199
Experiment 2: Aim: To test a resistor for ohmic or non-ohmic behavior.
Hypothesis: It is presumed that the resistor will show an ohmic behavior i.e. the voltage across the resistor is presumed to be proportional to the current through it.
Material:
- Resistor (Brown, black, black, brown, gold): 1000 Ω ± 5%
- Power supply
- Voltmeter
- Ammeter
- Wires
- Clamps
Variables:
Dependent variables: current
Independent variables: voltage
Controlled variables: Resistor, ammeter, voltmeter, power supply, wires
Method:
- A wire was connected from power supply to (mA) outlet of the ammeter.
- A second wire was connected from (com) outlet of ammeter to the resistor via a clamp.
- A third wire was connected from power supply to the resistor with the help of another clamp.
- Two wires were connected from resistor to voltmeter in parallel. One to (V) outlet and another to (com) outlet.
- The power supply was then turned on and the current in the ammeter was read at different voltage values which were set by adjusting the knob on the power supply equipment.
- Six different values were noted down.
Result:
Calculation 2: R = V/I
- R = 1
- R = 1
- R = 1
- R = 1.00
- R = 1.00
- 6. R = 1
Discussion: From calculation 1, it is evident that the resistance increases as the current in the circuit increases leading to increase in temperature. On the other hand, fig 1.1 shows a non-linear relationship between voltage and current, which is evidently a non-ohmic behavior.
As for the second experiment, calculation 2 shows that the resistance has remained constant throughout the experiment. Similarly, fig 1.2 shows a linear relationship between voltage and current, which is an ohmic behaviour.
Limitation: Temperature change in both bulb and the resistor could not be measured during the experiment, as temperature plays an important role for ohmic or non ohmic behaviors as stated above under “Ohm’s law”.
Improvement: In this experiment, the ohmic or non-ohmic behavior was tested using only one bulb and one resistor. For a better conclusion it might be reasonable to test ohm’s law with more than one bulb and resistor.
Conclusion: Experiment one: From the discussion and introduction, it could be concluded that the bulb shows a non-ohmic behavior since with increasing current, the temperature inside it increases and so does the resistance. The hypothesis is in agreement with the result, except for the fact that in this case, the bulb does not show any ohmic behavior initially either.
Experiment two: As mentioned earlier in the discussion, the resistor shows an ohmic behavior since increasing current does not lead to a significant increase in temperature in this case, and hence the resistance remains constant throughout the experiment. The hypothesis holds true with respect to the result gained from the experiment.
