SP212
Worksheet 19
Ch 28.2,3 Crossed Fields and the Hall Effect
Problem 1
A strip of copper has a free electron density of n = 8.47 × 1028 electrons/m3 , a thickness of l = 150 µm and
is 4.5 mm wide. It is placed i na B-field that is perpendicular to the strip (“pointing out of the board”) and
a current of i = 23 A is sent along it. What is the voltage drop across the width of the strip?
Problem 2
Starting from rest, an electron is accelerated through a potential difference whose magnitude is V1 = 1.2
kV. It then enters a region between two large parallel plates separated by a distance of d = 25 mm with a
potential difference across the plates of V2 = 170V . Due to the presence of a uniform magnetic field, the
electron travels in a straight line at constant velocity between the two plates.
a) What is the electron’s kinetic energy after being accelerated through V1 ? What is the electron’s speed?
b) What is the magnitude of the electrostatic force (the force due to the E-field) acting on the electron? If
the bottom plate is negatively charged and the top is positive, in which direction is this force pointing?
c) In unit vector notation, what is the magnetic field in the region between the plates?