Passage V

The current in an electric circuit produces a magnetic field that will exert a measurable force on a nearby magnet.

Students performed experiments using the apparatus shown in Figure 1.

The apparatus included an electric circuit. A horizontal segment of the circuit, Segment AB, lay between the poles of a horseshoe magnet, as shown in Figure 2.

When current flowed through the circuit, only the magnetic field associated with Segment AB exerted a measurable force on the horseshoe magnet.

The horseshoe magnet, which weighed approximately 1.5 newtons (N), rested on a scale. Before the first experiment and after each of the following scale readings, the scale was adjusted with the horseshoe magnet in place so that when no current was flowing through the circuit the scale reading was 2.00000 N.

Experiment 1

The students passed various amounts of current through the circuit and recorded the scale reading for each amount, as shown in Table 1.

Experiment 2

The students reversed the connections to the power supply so that the current flowed in the direction opposite to that in Experiment 1. They repeated the procedure used in Experiment 1. Their results are shown in Table 2.

Experiment 3

Using a current of 2.50 amp flowing in the same direction as in Experiment 1, the students varied the length of Segment AB. Their results are shown in Table 3.

Figures and tables adapted from Instruction Manual and Experiment Guide for the PASCO scientific Model SF-8607 and SF-8608Basic Current Balance and Current Balance Accessory. @1989 byPASCO scientific.