NORTHALLERTON COLLEGE

 

AS-LEVEL PHYSICS

 

 

Module PH3AS

 

 

ASSESSMENT:  RESISTIVITY OF PENCIL LEADS

 

 

 

Pencil leads are made from a mixture of graphite and clay.  Devise an experiment to measure the resistivity of a pencil lead (choosing just one from a range of hardnesses).

 

You should aim to plot a suitable graph; for example, to find the resistance and hence, the resistivity.

 

 

Useful equations:

 

V = IR    and R = V/I

 

r = RA/l    where                    R = resistance (W)

                                                V = potential difference (V)

                                                I = current (A)

                                                r = resistivity (Wm)

                                                A = cross-sectional area (m2)

                                                l = length (m)

 

 

 

 

 

 

 

AK Feb 08