Impedance spectroscopy of KBr

Team members

Laphas Precmcharoen, Song Runlin, Gao Jia

Idea

This project aims to determine the gravitational constant using the gravitational torsion balance based on the Cavendish Experiment

Materials

1. Thin, Lightweight Rod (~ 1 m in length)

2. Small Lead or Steel Spheres (~ 1 to 5 cm in diameters)

3. Large Lead or Steel Spheres (~ 20 cm in diameters)

4. Copper Wire (~0.05 mm in diameter ~ 30cm in length)

5. Small Mirror

6. Laser

7. Ruler or Photodiode array to measure the angle

8. Stable, Vibration-Free Mount

Procedure

1. Set Up the Torsion Balance:

  - Attach the smaller spheres to each end of the rod.
  - Suspend the rod horizontally from its center using the torsion wire. The wire should be attached securely to a stable mount.
  - Attach the mirror to the wire just below the mount.

2. Prepare the Large Spheres:

  - Position the larger spheres near the smaller ones.

3. Set Up the Laser and Photodiode Array:

  - Position the laser so that it shines on the mirror.
  - Set up the photodiode array at an appropriate distance so that it can detect the laser light reflected from the mirror.

4. Calibrate the Photodiode Array:

  - Shine the laser on each photodiode in the array and record the output. This will give you a calibration curve that you can use to convert photodiode signals into angles of rotation.

5. Perform the Experiment:

  - Carefully move the larger spheres closer to the smaller ones. The gravitational attraction will cause the rod to twist, turning the mirror and shifting the laser spot on the photodiode array.
  - Record the photodiode output at regular intervals.

6. Data Analysis:

  - Use your calibration curve to convert the photodiode signals into angles of rotation.
  - Calculate the gravitational constant using the observed rotation, the known mass of the spheres, and the properties of the torsion wire.