Introduction to the Undergraduate Physics Laboratory. Prof. Dr. Michael Ziese Head of the Undergraduate Physics Laboratory

Transcription

1 Introduction to the Undergraduate Physics Laboratory Prof. Dr. Michael Ziese Head of the Undergraduate Physics Laboratory

2 Undergraduate Physics Laboratory Prof. Dr. Michael Ziese Linnéstr. 5, R. 410 PGP, Prager Str / 741 ziese@physik.uni-leipzig.de

3 General Information Address: Undergraduate Physics Laboratory Prager Straße Leipzig Website: Username: Password: IPSPGP1 xxxxxxx

4 Objectives - Link mathematical concepts of physical reality with experimental practice - Introduction to handling of basic instruments - Introduction to basic data analysis techniques - Introduction to the analysis of measurement uncertainties

5 Organization Experiments are made in groups of two 4 h / Experiment: typically 8:30 12:30 6 days in the lecture free time Lab reports are usually finished within the lab hours

6 Experiments ( 6 in total) Mechanics: M1e: M2e: M3e: M7e: M12e: M17e: Data Analysis Video Analysis of Accelerated Motion Ultrasound Viscosity Measurements Coupled Pendulums and Degree of Coupling Pohl s wheel (linear and nonlinear oscillations) Thermodynamics: W9e: W15e: W18e: Specific Heat Capacity of Solids and Liquids Isotherms of Real Gases Heat Capacity Ratio Important! To be able to use Origin and access the internet on our notebooks, you have to log in to the eduroam Wifi. Therefor you ll need your uni- as user and the corresponding password.

7 Laboratory Order 1. Read the Laboratory Order as well as the Notes on Safety and Laboratory Records. In the first lab session you will have to confirm with your signature that you were informed on/have familiarized yourself with laboratory order, safety precautions and evacuation procedures. 2. Time tables are published on the Undergraduate Laboratory Website and are binding. Be on time. Everybody 15 min late will be excluded. You are responsible for arranging repeat dates. This also holds for illness and exclusion because of insufficient preparation. 3. The experiments are performed in groups of two students. Every student is requested to use an A4 size bound notebook for the protocols; files with lose sheets are not accepted. In general the protocol is finished during the corresponding lab session.

8 4. It is expected that every student prepares at home for the experiment: - preparation of the protocol - preparation of the physical basics The physics basics necessary for the understanding and accomplishment of the experiment will be controlled. If the knowledge is insufficient, you will be sent home. 5. Please use instruments and equipment of the Undergraduate Physics Laboratory with care. Defects have to be reported immediately. Do not repair anything yourself.

9 6. Do not cheat. Especially, do not bring old protocols to the lab. 7. You will have to perform 6 experiments. Each experiment will be graded on a scale from 0 to 12 points. Grades are recorded on a form and are certified by the signature of the supervisor. The form will have to be returned at the end of the course. The final grade is obtained by taking the arithmetic mean of points and using the following conversion scale: 12 P = 1.0, 11 P = 1.3, 10 P = 1.7,, 4 P = 3.7, 3 P = 4.0, < 3 P: Offences against the Laboratory Order might lead to a student being suspended from the laboratory course.

10 Grading Final Grade = Average of 6 Single Grades

11 Complete safety regulations see website. Basic Rule In the laboratories, behave in such a way that you do not endanger yourself and others. Read before the 1. lab session. Fire hazards Smoking is not allowed anywhere in the building. All organic solvents must be stored at a sufficient distance from heating equipment. In any cases of fire, ring the nearest fire alarm, and leave the building immediately.

12 Electric Hazards All electrical circuits have to be checked by the demonstrator before the experiment may be started. Always give attention to safety if you are using dangerous voltages (> 40 V DC and > 60 V AC) and special attention working at high voltages (> 300 V). Compressed Gases Gas from compressed gas cylinders might displace oxygen and lead to suffocation. Ensure sufficient ventilation. If main valve is damaged, compressed gas cylinders turn into rockets. Do not tamper with the valve and the pressure regulator. Compressed gases may only be used after first consulting a demonstrator or technician. Pressure regulator

13 Laser Hazard Laser Radiation > Class 1: Never look directly into the direct or reflected laser beam. Eye protection by laser safety spectacles is necessary if there is a possibility of either direct or reflected radiation entering the eye. In case of class 4 lasers safety spectacles do not protect the eyes against direct radiation. Class Description 1 The accessible laser radiation is nonhazardous or the laser is enclosed in a casing. 2 3R 3B The accessible laser radiation is in the visible range (400 nm to 700 nm). It is nonhazardous even for the eyes in case of a short (less than 0.25 s) exposure. The accessible laser radiation is hazardous for the eyes. The accessible laser radiation is hazardous for the eyes and in some cases also for the skin. Diffusely scattered light is in general nonhazardous. 4 The accessible laser is very hazardous for the eyes and is hazardous for the skin. Even diffusely scattered radiation might be hazardous. The use of these lasers often involves fire and explosion hazards.

14 Laboratory Record Laboratory as bound A4-book contains: - Tasks - Basic Physics Preparation before the lab session! - Measurement values During the lab session. - Analysis - Measurement uncertainty - Results and discussion see Laboratory Records Measurement uncertainty on the website.

15 Measurement Uncertainties

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17 Literature W. Schenk, F. Kremer Physikalisches Grundpraktikum (in German) I. G. Hughes und T. P. A. Hase Measurements and their Uncertainties GUM: Guide to the Expression of Uncertainty in Measurement

18 Data Analysis Software: - Software Origin Campus-License (7.5 / 8.1): Origin demo (9.1) - Free Alternatives: QtiPlot ( SciDavis (

19 An Introductory Example: Incline and Brachistochrone Which track yields the largest terminal velocity?

20 Analysis of the motion on the incline x-axis along the incline Raw data of the video analysis program x y 0.5 x,y (m) Zeit t (s)

21 x-axis along the incline Position Velocity Acceleration x (m) dx/dt (m/s) d 2 x/dt 2 (m/s 2 ) Zeit t (s) Zeit t (s) Zeit t (s) v dx dt 2 dx a dt 2

22 Alternative analysis: x vs. t Equation Weight Residual Sum of Squares y = a + b*x No Weighting Adj. R-Square Value Standard Error I Intercept I Slope x (m) t 2 (s 2 )

23 Analysis of the motion on the Brachistochrone x y r( sin ) r( 1 cos ) Rolling on on a circle with constant angular velocity w: wt X 0.2 x, y (m) Y time t (s)

24 A Measurement is never exact!!! Measurement uncertainties: Systematic (Type B): - Non-ideal measurement principle: idealizations, approximations, etc. - Problems with the calibration Statistical (Type A): - Fluctuations in uncontrolled variables - Noise: Thermal, Johnson, shot, telegraph, 1/f noise - Quantum fluctuations

25 Fundamental constants (2010) (NIST) Newton s Gravitational Constant: G = x ± x m 3 kg -1 s -2 (1.2 x 10-4 ) Planck s Quantum: h = x ± x Js (4.4 x 10-8 ) Elementary Charge: e = x ± x C (2.2 x 10-8 ) Avogadro s Constant: N A = x ± x mol -1 (4.4 x 10-8 ) Boltzmann s Constant: k B = x ± x J K -1 (9.1 x 10-7 ) Electron g-factor: g e = ± (2.6 x ) [concise: g e = (53)]