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

An experiment to find the Resistivity of Pencil leads in different degree of hardness

Extracts from this document...

Introduction

An experiment to find the Resistivity of Pencil leads in different degree of hardness

Introduction:

A lead pencil, is not really made of lead, instead, it is made from graphite, which is a form of carbon. Carbon is one of a class of substances that will conduct electricity, like a conductor, but will also block some current.

(the parameter in about why under what circumstances it does not conduct)

Aim:

The aim of this experiment is to find out the resistivity with different hardness of graphite (pencil leads, which relates to quantity of carbon in the lead). To measure the resistance of the lead, the ohm’s law equation will be used R= V/I (despite heat having been produced)

  , then

Using the equation: A (Cross-sectional area) R (resistance)/ L (Length) =ρ (Resistivity)

ρ=    A R     image00.png

        L

Preliminary Work:

In order to find out the range of voltage to be used, the following data shows the result from the experiment of HB pencil lead.

Power Supply Unit (volts)

Current (amp)

Voltage (volts)

1

0

0.1

2

0.01

0.8

3

0.05

1.62

4

0.08

2.49

5

0.11

3.39

6

0.14

4.33

7

0.18

5.24

8

0.22

6.15

9

0.26

7.06

10

0.30

7.79

From the table above, it shows there is a significant dropped in the amount of voltage after the

...read more.

Middle

image28.pngimage22.png

image02.png

image03.png

image01.pngimage04.png

Clay that is a good insulator of electricity so I think this may affect the resistance characteristic but if the graph were to look like this it is because carbon is a semi conductor. This is due to that there is a distinct possibility that the pencil lead may have the characteristics of a semi conductor, as carbon is a semi conductor. From the graph above, to find the gradient I would use the results from the point (0,0) up until the line starts to curve.

  • Pure graphite is classed as a semi-metal and has a typical electrical resistivity of 3x10-5 ohm-m. Most pencil cores are a mixture of graphite and clay. (Predict the proportion of clay to graphite from your results?)
  • The Higher the resistance of a pencil lead, the lower the resistivity it has

Variables:

Independent variables:

  • Different types of pencil??

When conducting this experiment I will alter only one variable at a time and keep the other variable constant at a fixed measurement. This will enable me to draw conclusions from my results. When changing the hardness of the pencil, HB, 4B and 8B, I will keep the length of the pencil the same as possible.

...read more.

Conclusion

.jpg" style="width:301.27px;height:226px;margin-left:0px;margin-top:0px;" alt="image31.jpg" />image07.pngimage10.pngimage09.pngimage08.png

3.

image32.jpgimage14.pngimage13.pngimage12.png

image33.jpgimage15.png

4

.

Set HB pencil in a parallel circuit(with voltmeter and ammeter)

image35.jpgimage24.pngimage19.pngimage18.pngimage17.pngimage16.pngimage34.jpgimage20.pngimage21.pngimage23.png

5

Change the unit on the power supply from 2-6

image36.jpgimage25.pngimage26.png

6

Record both readings on voltmeter and ammeter

image37.jpgimage38.jpg

7

Repeat the same steps for 4B, and 8B.

8

Repeat the same methods order again for each pencil for second trial.

9

Repeat the same methods and order again for each pencil for final trial.

Safety

To maintain safety in the lab, current passing through the graphite should be checked out that it must not be over 1 amp, this is because the current will make the electrons flowing flow at a faster rate creating friction through the graphite which could make it burn, which means that we should not use a range of 10v or above with the power supply. Also the experiment will be well away from any taps, and liquid. This is precautions, to prevent injury. But the risks from this experiment are not that great.

...read more.

This student written piece of work is one of many that can be found in our International Baccalaureate 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 International Baccalaureate Physics essays

  1. Marked by a teacher

    Experiment to calculate the diameter of a piece of nichrome wire from its electrical ...

    3 star(s)

    Average trendline of Length vs. Resistance: Graph 2. Maximum and Minimum trendline of Length vs. Resistance: [KD4] More sample calculations: Sample calculation 4. Calculating the percent uncertainty of the average gradient: Sample calculation 5. Calculating the diameter Conclusion: From the graphs 1 and 2 above, it is evident that the

  2. To test the ohmic and non-ohmic behavior in a resistor and a bulb

    R = 1 3. R = 1 4. R = 1.00 5. R = 1.00 6. 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.

  1. Resistance Lab. Aim - To investigate the effective resistance (total resistance) of ...

    ==> Conclusion - Thus from the above experiment we can conclude that the effective resistance of the 3 resistors connected in series, using both ways, was approximately 40 ohms. This can clearly be seen from both values of the average effective resistances, calculated separately.

  2. RESISTIVITY OF A MATERIAL

    It is equals to1.46�10-7m2 . The average resistance is 0.268?. So use the formula, is variable, so is equals to1.3�10-8?m. The criteria value of the resistivity is, so our experiment error is 23.5%. Skills: Manipulative skill: When we change the wire to do the experiment, we must turn off the power first.

  1. Conservation of Momentum Experiment.

    the cue puck had no y components to it, but in reality, this is not true, it would be nearly impossible for the manually controlled puck to have travelled perfectly in a straight line, this flaw can be found on the data paper (dots made by the pucks), as the

  2. Investigating Wires

    If the resistance becomes too low, there is an excessive flow of current which causes the wire to melt from the excess heat. Therefore time affects the resistance per unit length, and so it was kept constant.

  1. How does the sinkage depth of a tyre affect its rolling resistance ?

    The degradation in the force is caused by the increased rolling resistance due to the sinkage depth . (bedenbender , 2012) As the tire roates under the weight of the vehicle , the tire experiences continuous cycles of deformation and recovery .

  2. HL Physics Revision Notes

    Explain the operation of a basic alternating current (ac) generator The coil if wire rotates in the magnetic field due to an external force. As it rotates the flux linkage of the coil changes with time and induced an e.m.f. Discuss what is meant by the root mean squared (rms)

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