Measuring properties of some material An experiment was carried out to determine
ID: 1459541 • Letter: M
Question
Measuring properties of some material
An experiment was carried out to determine the electrical properties of a new conducting material. A bar was made out of the material, L = 18 cm long with a rectangular cross section h = 2 cm high and w = 0.7 cm deep. The bar was part of a circuit and carried a steady current (the diagram shows only part of the circuit). A uniform magnetic field of 1.7 tesla was applied perpendicular to the bar, coming out of the page (using some coils that are not shown). Two voltmeters were connected along and across the bar as shown. The reading on Voltmeter 1 is V1 = +0.45 volt. The reading on Voltmeter 2 is V2 =+0.00027 volt. The connections across the bar for Voltmeter 2 were carefully placed directly across from each other to eliminate false readings corresponding to the much larger voltage along the bar. There is only one kind of mobile charge in this material.
Remember that a voltmeter gives a positive reading if the positive lead is connected to a higher potential location than the negative lead.
Explanation / Answer
length of the bar L=18cm
height of the bar h=2cm
width of the bar w=0.7cm
magnetic field B=1.7T
reading on voltmeter1 v1=0.45v
reading on voltmeter2 v2=0.27mv
b)
drift veleocity vd=v2/B*w
=0.27*10^-3/(1.7*0.7*10^-2)
=0.0227 m/sec
c)
mobility u=vd/E
u=vd/(v2/w)
=0.0227/(0.27*10^-3)/(0.7*10^-2)
=1.2*10^4 m^2/V.sec
d)
let,
current i=0.9 A
no of charges n=i*B/(q*V2*w)
n=(0.9*1.3)/(1.6*10^-19*0.27*10^-3*0.7*10^-2)
n=3.87*10^24 no of chrages per m^3
e)
v1=i*R
0.45=0.9*R
===> R=0.5 ohms
resistnace R=0.5 ohms