Passage V

When an electrical current flows through a metal strip in a magnetic field, a magnetic force is exerted on some electrons in the strip. These electrons are pushed to an edge of the strip, making that edge negatively charged (see Figure 1).

The opposite edge of the strip, which develops a shortage of electrons, becomes positively charged, and so a voltage, V_H ,develops between these 2 edges of the strip.

A physics class conducted 3 studies of this phenomenon, called the Hall effect.

In each trial of the studies, an aluminum strip having a thickness d was clamped to a ring stand. The 2 ends of the strip were connected to an electrical circuit containing a DC power supply, and the 2 edges of the strip were connected to a voltmeter (see Figure 2).

The strip was also positioned horizontally between the poles of an electromagnet (see Figure 3).

The students adjusted the power supply output as needed so that the desired current, I, flowed through the strip. Finally the students adjusted the electromagnet as needed to produce the desired magnetic field strength, B, and recorded he resulting V_H.

Study 1

With d equal to 15 mm and B equal to 0.6 tesla (T) the students found V_H, in nanovolts (nV; I nV= 10^-9 V) for various I, in amperes (A) (see Table 1).

Study 2

With d equal to 15 mm and I equal to 25 A, the students found V_H for various B (see Table 2).

Study 3

With B equal to 0.6 T and I equal to 25 A, the students found V_H for various d (see table 3).