• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Investigating The Resistance Of A Light Bulb As The Voltage Is Increased.

Extracts from this document...


Investigating The Resistance Of A Light Bulb As The Voltage Is Increased.

Resistance is the resist of electrons flowing through an electrical component. The resistance slows down flow meaning that the components will heat up due to friction. The current in a circuit gets smaller the bigger the resistance is. To work out resistance you can use this formula Resistance = Volts/Current, R=V/I

To measure the resistance in a circuit you would need to find out what the voltage and the current is in the circuit. To find the voltage of an light bulb in a series circuit and hence the voltage of the circuit you would need to use a voltmeter which would be connect parallel with the light bulb to find the voltage across the bulb (see diagram below). Then you would need to find the current in the series circuit by placing an ammeter in the circuit which would give you the current of the circuit as well as the bulb current (see diagram below) Now you would then divide the volts by the amperes to find the resistance.  

Voltmeter and Ammeter in a circuit diagram


...read more.


Below are the results from the preliminary work and a line graph on the next page shows the results in a line graph.

Voltage (V)

Current (I)

Resistance (Ω)







































Current results 1 in Amperes

Current results 2 in Amperes

Current results 3 in Amperes

...read more.


These results show that if the resistance on the resistance graph is too high it will then be lower on the current graph.

I think that some results are wrong due to the rheostat being unreliable.  One reason for this could have been that the rheostat could have had a loose connection.  Also the coiling of the wire in the rheostat could have become pulled apart with use and this could make the rheostat inaccurate.   I tried to avoid this by checking if any rheostats worked better but they did not work as well. To have solved this the school could have had some new rheostats.

My results were good enough to support the prediction and for this reason I think my investigation was worth carrying out.

Further work to this experiment could have been done with a new reliable rheostat which would give me more accurate results. Also I could have changed the make of the light bulb to see if a different make of light bulb would have given similar results and verified the prediction.  Using a different light bulb may give different results as the metal filament may be different but the general pattern should be the same.

Patrick Pitts

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. To Investigate How the Resistance of the Light Dependent Resistor Depends On the Current ...

    In my prediction, I stated that: If the light bulb becomes brighter, the resistance of the LDR decrease. From my graph on the previous page, it shows that I am right. I can see that the resistance of the LDR is in strongly correlation to the current of the light bulb after 25MA.

  2. Investigation into the resistance of a filament lamp.

    I will find the percentage error of my result to show how accurate my results are. Method: i. Get the apparatus that are listed above ii. Connect the connecting wires to the DC power supply iii. Set the power supply to 12V iv.

  1. resistivity if a nichrome wire

    I then got the following results: Maximum gradient: 9.3 ? / 0.575 = 16.2 ? m-1 Minimum gradient: 9 ? / 0.626m = 14.4 ? m-1 I will now work out the percentage error for the gradient of the graph resistance against gradient.

  2. Relationship between the current and voltage.

    and current. This graph was also a straight-line graph, with a positive gradient, which means that the resistance was a constant. This means that ohms law is applicable, as it should be, as the temperature of the circuit was kept constant, was high voltages were not used.

  1. Investigating Ohms law

    2.00 146.4 2.00 146.6 2.20 154.1 2.20 153.7 2.20 153.6 2.20 153.8 2.40 160.7 2.40 160.8 2.40 160.8 2.40 160.8 2.60 167.5 2.60 167.3 2.60 167.4 2.60 167.4 2.80 174.0 2.80 173.8 2.80 173.7 2.80 173.8 3.00 180.0 3.00 180.2 3.00 180.0 3.00 180.0 3.20 186.1 3.20 186.0 3.20 186.1

  2. Free essay

    Resistance of a wire

    To get the most accurate readings from our ammeter and voltmeter we used digital models to get results to the 2nd decimal point. Temperature surroundings have to be taken into consideration as they are almost impossible to maintain perfectly. Sunlight frequently shone through the windows and this could have easily caused slight but important differences in the wire resistivity.

  1. Investigating how temperature affects the resistance in a wire

    Instructions: 1. Set up the apparatus according to the diagram as above. 2. Fill the kettle with tap water and turn it on, making sure that throughout the experiment it is on and full of hot water. 3. Wrap the steel wire around one of the wooden splints leaving two ends on the same side.

  2. Investigating the effect of 'length' on the resistance of a wire

    two screws will be screwed into the wooden plank at either ends of the ruler, the screws will also be touching the ruler. The wire chosen for the experiment will be tied around the screws more than once, to ensure that the wire is taut and has no kinks to give better accuracy in the results.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work