scientific
4
012-04046C
Current Balance and Accessory
carefully lower the arm to reposition the Current
Loop in the magnetic field. Six Current Loops are
supplied with the SF-8607 Basic Current Balance
Kit. The lengths are:
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
The lengths above were measured at the maximum
length of the current-carrying wire foil. The effective
length may be somewhat shorter, as much as 0.2 cm for
single lengths and 0.4 cm for doubled lengths (doubled
lengths refer to Current Loops in which the current
passes between the magnet poles twice, once on each
side of the PC board).
Lab Stand
0.01 gram
Balance
SF-8608
Accessory
Unit
Magnet
Assembly
Figure 8 Setup for the SF-8608 Current Balance
Accessory.
Main Unit
0
2 0
4 0
6 0
8 0
1 0 0
-1.36e-20
1.00e-1
2.00e-1
3.00e-1
4.00e-1
5.00e-1
6.00e-1
Length, mm
g
Force vs Length for SF-8607
0
1
2
3
4
5
6
7
0.00
0.05
0.10
0.15
No. Magnets
,g
Force vs No. of Magnets for SF-8607
Two different lengths of loop
Figure 6 Typical Data for Force versus Wire Length
Measurements
Figure 7 Typical Data for Force versus Wire Length
Measurements
Varying the Magnetic Field
The magnetic field is varied by changing the number of
magnets that are mounted on the Magnet Assembly. (We
recommend you mark the north pole of each magnet, to
help students during setup.) The magnetic field strength
may not be exactly proportional to the number of mag-
nets, but it is reasonably close, as seen by the data in
Figure 7.
SF-8608 Current Balance Accessory
Using the SF-8608 Current Balance Accessory, you can
determine how the angle between the current-carrying
wire and the magnetic field affects the force between
them. The basic experimental setup is shown in Figure 8.
➧
Note: The SF-8608 Current Balance Accessory
can also be used to experiment with the relationship
between current and force by holding the angle
steady and varying the current.
➧
Warning: The current through the SF-8608
Current Balance Accessory should never exceed
2.0 amps.
➀
Set the dial on the unit to 0
o
.
➁
Align the Magnet Assembly so that the magnetic field
is approximately parallel with the wires of the coil.
➂
With the current turned off, measure the weight of the
Magnet Assembly, or if you are using an electronic
balance, tare the balance.
Set the current to a value of 2.0 amps. Take a new
reading and record this in your data table. Rotate the
dial clockwise in 5
o
increments, taking new readings
each at each setting. Then rotate the dial counter-
clockwise in 5
o
increments. The resulting graph of
Force vs Angle should be a sine curve.
➃
