Lab 5

Frank Hertz Experiment

 

 

 

 

 

 

Bill Chun Wai Hung

Nimish Kumar

 

 

Friday Section

 

13 May 2004


Data:

Valley

Voltage (eV)

Voltage Difference (eV)

1

8.597

N/A

2

13.092

4.495

3

17.823

4.731

4

22.923

5.100

 

Calculation:

The average voltage difference is eV

The percentage difference is

Conclusion by Bill Chun Wai Hung:

1. Principles and Results

The voltage value of the valleys of the graph is measured to by 4.495eV, 4.731eV, and 5.100eV. The average voltage difference is 4.775eV. The percentage difference is 2.54%.

 

  By using the Franck-Hertz Apparatus, the electrons are shot from one end and if the electrons have enough energy, then they will pass the repulsion force generated by the potential difference from the battery. By measuring the amount of electron passing through the potential barrier, the energy level from the emission of light from mercury can be measured.

 

  From the computer-generated graph, there are peaks and valleys representing the current passing through the circuit. The different amount of current passing through the circuit is depended on the amount of electron that successfully reached the target plate. In other words, by calculating the difference of the valleys, the difference of energy level of the ”°higher energy electrons”± can be determined.

 

The target value of the mercury energy level is 4.9eV, and the experimental mercury energy level is .4.775eV.

 

2. Error Analysis

The electronmeter are so sensitive, so the electrical equipments surrounding the electronmeter can actually interfere with the measurement of the result. This is because when a wire is moved, the current in the wire generates a magnetic field, and the magnetic field interferes with the reading of the electronmeter. However, in the case of this experiment, the equipments and wires are not moved, so the reading of the electronmeter is not affected too much.

There was an intrinsic error during the time the experiment was performed. Dr. Jordan and his students could not find out the problem exactly, but the reading of the voltage continued to go up for the earlier readings. The reading obtained by this report is a more accurate reading from the laboratory.