• 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...


Neil Fraser        Science        Mr Fox

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


Resistance is the confrontation of electrons flowing through an electrical component. The resistance slows down the flow through the component, due to the friction created. The current in a circuit gets smaller the bigger the resistance is.

To work out resistance you can use this formula:

  Ohm’s Law – R= V           (Resistance = Voltage/ Current)


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 a light bulb in a series circuit and hence the voltage of the circuit you would need to use a voltmeter, which would be connected in 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.)

To find the resistance of the circuit, you would then divide the voltage by the current.

For this experiment I will be using a series circuit rather than a parallel circuit.

...read more.


The diagram below shows inside a piece of wire showing the free electrons-the flow- and the metal ions. If the temperature is increased then the free electrons in the diagram will hit the metal ions more creating more resistance. If the thickness of the wire was changed i.e. when the metal is thinner the free electrons will have a smaller area to pass through and will hit the metal ions more and so there is greater resistance, than in a thicker wire where there is a greater area for the electrons to pass through. Therefore it will be easier for the free electrons to move through a thicker wire and the resistance is therefore lower.

I believe that if the Voltage and/or the current are increased then the light bulb filament will get brighter and the resistance will go up because the temperature changes. This breaks ohms law as the temperature changes so therefore the resistance will change. You can tell that the temperature rises because of the colour of the light bulb filament. If the light bulb filament is an orange colour at around 2 volts

...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.

...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. Using an LDR to detect the intensity of plane polarised light allowed through a ...

    Since I have a result for crossed polaroids, which is supposed to equal zero, the light that has gotten to the LDR must be through ambient light. Hence, we require a reading for 7.30V, which is equal to approximately 9.5 lux.

  2. An Investigation To Show How the Voltage Affects the Current In a Light bulb.

    The leads are metal conductors; increased vibrations means that it will be harder for current to flow as the electrons will collide with the vibrating atoms more. The collisions will slow the electrons down; this is resistance. The resistance of a filament lamp increases as the temperature of the filament lamps increases.

  1. Investigating Ohms law

    12.10 5 14.50 5 13.60 6 17.20 6 14.90 6 17.70 6 16.63 8 23.80 8 20.80 8 24.20 8 22.93 10 39.00 10 34.10 10 39.60 10 37.57 12 67.50 12 65.80 12 69.80 12 67.70 Light bulb Repeat 1 Repeat 2 Voltage (V)

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

    � (0.11 � 10-3)2/4 = 9.5�10-9m2 As explained in my plan, if the resistivity of a material is known, the resistance of a given length and cross-sectional area can be calculated. Resistance = constant (resistivity) �length Area of cross-section ~Analysing Evidence and Drawing Conclusions~ GRAPH No1: Graph of first and second readings...

  1. Investigation into the resistance of a filament lamp.

    which causes the amount of current drawn by the lamp to stabilise and the lamp to emit a stable light output. Depending on the size of the filament, the in-rush period can be from tens of milliseconds to hundreds of milliseconds.

  2. Does a light bulb obey Ohms law.

    I will record the results shown on the ammeter. This is the circuit I will be using to perform my experiment: Fair Testing: To ensure my experiment is a fair test I will use all of the same equipment for the whole experiment.

  1. resistivity if a nichrome wire

    = gradient x area (See graph paper) The graph shows a steady increase in the resistivity of the wire, hence, positive correlation. This suggests that there were no anomalous results in my readings as all the points in the graph were flowing.

  2. How the resistance of a filament bulb varies its current flowing through it

    Than it from the point onward from 4 volts it is bright till 8 volts then there was too much pressure and the bulb burst. Over here the result for the resistance is totally out of range. Analysis- as I observed the result I saw very different pattern.

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