Experiment 31: Magnetism
To study the relationship between magnetic force and the magnitude of the current, length of the wire, strength of the magnetic field, and the angle between the field and the wire.
SF-8607 Basic Current Balance (Main Unit, 6 Current loop PC boards, Magnet Assembly with 6 magnets), DC power supply, DC ammeter, Balance, Lab Stand, hook-up wires with banana plug connectors
A current-carrying wire generates a magnetic field surrounding the wire. When this wire is placed in an external magnetic field, it experiences a force due to the poles of the two magnetic fields interacting. The magnitude and direction of this ...view middle of the document...
With current flowing, the reading will be higher or lower than before. The difference in weight (FI - F0) is proportional to the force exerted on the magnetic field (and thereby the magnets) by the current-carrying wire. To investigate the relationship between current and force, vary the current and measure the weight at each value.
1. Check that the equipment is connected as shown in Figures 1 and 2. Make a table on your raw data sheet to record the current, I, in amps, the mass, m, in grams, and the mass equivalent to the magnetic force, FM, in grams. (See Table 1 below.)
2. Select a current loop, and plug it into the ends of the arms of the Main Unit, with the foil extending down as shown in Figure 1.
3. Place the Magnet Assembly on the balance. Position the lab stand so the horizontal portion of the conductive foil on the current loop passes through the pole region of the magnets. Make sure the current loop doesn't touch the magnets.
4. Measure the weight of the Magnet Assembly with no current flowing (F0).
5. Set the current to 0.5 Amp. Determine the new "mass" of the magnet assembly. Record this value under "Mass" in your data table. Subtract the mass value with the current flowing from the value with no current flowing. Record this difference as the "Force."
6. Increase the current in 0.5 Amp increments to a maximum of 5.0 Amp, each time recording the current, “Mass” and calculating the “Force”.
Table 1 Data
|Current |“Mass” |“Force” |
|(amps) |(grams) |(grams) |
|0.0 | | |
|0.5 | | |
|1.0 | | |
|... | | |
| | | |
| | | |
Procedure Part II. Force versus Length of Wire
You can vary the wire length by using one of the six different current loops. The lengths for each current loop are given in the following table:
|Current Loop |Length |
|SF 40 |1.2 cm |
|SF 37 |2.2 cm |
|SF 39 |3.2 cm |
|SF 38 |4.2 cm |
|SF 41 |6.4 cm |
|SF 42 |8.4 cm |
Changing Current Loops:
1. Copy Table 2 onto your data sheet. Swing the arm of the Main Unit up, to raise the present current loop out of the magnetic field gap. Pull the current loop gently from the arms of the base unit. Replace it with a new current loop.
2. Determine the length of the conductive foil on the current loop by referring to the table above. Record this value under "length" in Table 2.1.
3. With no current flowing, determine the...