Tomsk Polytechnic University. PHYSICS II Reports on Laboratory Experiments

Transcription

1 Tomsk Polytechnic University PHYSIS II eports on Laboratory Experiments Tomsk 00

2 UD 53 (076) PHYSIS II. Electricity and Magnetism. Electromagnetic Oscillations and Waves. eports on Laboratory Experiments. Tomsk: TPU Press, 00, 3pp. These instructions have been approved by the Department of Theoretical and Experimental Physics and the Department of General Physics of TPU Authors: V. M. Antonov V.A. Dolgikh V. F. Pichugin eviewed by: V.Ya. Epp, Professor of Department Physics and Mathematics, TSPU, D.Sc.

3 All the laboratory experiments must be performed in the TPU Physics Laboratory. The estimation of students laboratory activity is based on their ability to perform the laboratory experiment and to present the results in conventional format. The report must be carefully prepared. It must include all the measurements and calculations. List of laboratory experiments. Studying of an Electric Field. Determination of the Ionic harge of Hydrogen 3. Measurement of apacitance and Permittivity by Bridge Method 4. Determination of High Value esistance and apacitance with the Help of elaxed Oscillations 5. Study of Semiconductor esistance-temperature Dependence. Determination of Activation Energy. 6. Measurement of a Solenoid Magnetic Field Strength. 3

4 eport on Laboratory Experiment No Electric Field esearch The student: Group _ First name Last name is allowed to do the laboratory work. Date Purpose of Work Determine disposition and potentials of electric field equipotential surfaces produced by plane and cylindrical electrodes. Graphically plot electric field strengths on the basis of the measurements. Devices and Instruments Galvanometer, measuring circuit, electric bath, electrodes of the plane and cylindrical forms, plotting paper. Theoretical ontents. Summary Electric field is Field strength is Electric field potential is Equipotential surface is 4

5 Electric field strength and potential relation - Method of electric field research - Principle of determination of the equipotential surfaces - Electric Scheme 4 - D -_ Table of symbols E - E 6 - E G - U - - Tr. - _ Scheme of the Electrode's Allocation in the Electrolytic Bath. A - Table of symbols U - _ B - _ alculation Formulas. Potential of the equipotential surfaces produced by plate electrodes 5

6 = where U l x. Potential of the equipotential surfaces produced by cylindrical electrodes = where U d x a Measurement esults Necessary data for calculation of potential are determined from graphics of equipotential surfaces. esults of measurements and calculations are recorded in tables.. Plate electrodes. Order of equipotential surfaces x Distances U (Volt) Table (Volt). ylindrical electrodes Order of equipotential surfaces x Distances d U (Volt) Table (Volt) 6

7 Measured by the student: Verified by the teacher: Note: Graphics of field lines are enclosed with this report. esume Name Test Questions. Give a definition of the term: an electric field.. Give a definition of the term: field strength. 3. Give a definition of the term: potential of electric field. 4. How are the field strength and potential at a given point of field mathematically connected? 5. Prove that field lines and equipotential surfaces are mutually perpendicular. 6. What surface is called equipotential? 7. What electric field is called potential? 8. How do electrode forms influence the electric field? 9. What electric field is called uniform? Answers 7

8 Executed by the student: Group First name_ Last name_ Approved by the teacher: Date 8

9 eport on Laboratory Experiment No Determination of the harge of Hydrogen Ion The student: Group _ First name Last name is allowed to do the laboratory work. Date Purpose of Work Determine the charge of hydrogen ion and compare it with the elementary charge. Devices and Instruments Hoffman s voltmeter, rheostat, source of direct current, milliammeter, switch, connecting wires. Theoretical ontents. Summary Electrolysis is the phenomenon The ions of hydrogen are produced as a result of electrolysis of aqueous solution of sulphuric acid H SO 4. According to the reaction Molecules of oxygen appear near the anode as a result of the following process harge of ion can be determined where Q - _ n - alculation Formulas (with explanation of values which are used) TIt q, N P 0 H V V I _ t N 0 T _ 9

10 P P gh ap, H aт t gh P t _ a _ Experimental Assembly where K, K k _ ma V Measurement esults exp I [A] T [sec] T [ 0 K] V [m 3 ] P at [kpa] Average value h [m] P h [kpa] P t [kpa] P H [kpa] q + [] Measured by the student: Verified by the teacher: Name Analysis Let s introduce experimental results into the formulas and calculate the charge of hydrogen on: q q q Let s compare the calculated results with the value of elementary charge: 0

11 esume Absolute and ratio errors of the value of q for the experiment are: q q T T I I t t P P H H V V Basis of errors: T SM 0,95 T ; where T =, since value of T is measured with accuracy _ k I 0, 95 I _, where I I max 00% ( k grade of accuracy of device, I limiting value of the device scale) max k, I t SM 0,95 t _, where t, since value of t is measured with accuracy max ; P H ( P at) ( gh) (0,9P T ) P at 0,95 _, where, P at since value of P at is measured with accuracy h 0,95 h, where h, since value of h is measured with accuracy P T 0,95 _, where, P t is defined in the following way: 0 at temperature ( t ) value of P (from Table) at temperature 0 ( t ) value of P t t Pt Pt P t V 0,95 V, where V, since value of V is measured with accuracy q q q P t P at

12 Final esult q q with probability 0,95. Test Questions. What is the value of elementary charge?. What is the effect of electrolytic dissociation? 3. Formulate the first Faraday law. 4. What charge type has the ion of hydrogen? 5. Where would be larger the volume of evolved gases, near cathode or anode? Why? 6. You mix the acid and water. The order of mixture: the first component is acid and water is the second. Why is such order used? 7. What influences the value of the electrolyte conductivity? Answers Executed by the student: Group First name_ Last name_ Approved by the teacher: Date

13 eport on Laboratory Experiment No 3 Measurement of apacitance and Permittivity by the Bridge Method The student: Group _ First name Last name is allowed to do the laboratory work. Date Purpose of work: capacitance measurement of two capacitors, capacitance of capacitors in series and parallel connection and permittivity of a substance. Devices and instruments: sound-frequency generator, oscillograph, two standard capacitors, two capacitors to be investigated, plane air capacitor, dielectric plates, variable resistor, trammel, ruler. Theoretical ontents. Summary apacitance is Permittivity of a substance is 3

14 A bridge method of capacitance measurement means In the capacity of the null-voltage indicator is being used. For the reason will get, where The electric scheme of a capacity bridge is shown: Table of symbols: С С SG О To measure the permittivity of a substance is used. 4

15 Table of symbols: d 0 d d The permittivity is calculated by using the capacitance bridge method where - d - 0 S - d - esults of the Measurements and alculations of apacitances Investigated capacitance (Ohm) (Ohm) (Ohm) Table. Value of capacitance (microfarad) x x xp (in parallel) xs (in series) Measurement esults of the Permittivity of a Substance Dielectric d 0 (mm) d (mm) d (mm) S (m ) (picofarad) Table. alculations of the apacitances 5

16 x x xp xs Let's compare the results of measurements basis of the measured x and x. Measurements xp and xs with the calculations on the alculations alculations of the Permittivities of Substances omparison with the Table esults Table data Glass 57 Viniplast,5 Data you've got Analysis of Measurements Let's calculate precision of measurements by using the estimation method of indirect measurements. Formula construction for the uncertainty of measurement Evaluation of inaccuracy of measurements Measurement's results: x with the probability 0, 95 x x 6

17 atio error of measurements: esume Test Questions. Why is the capacitance of a capacitor larger than the capacitance of an electric conductor?. Which parameters influence the permittivity of a substance? 3. What preferences do you get using the bridge method for the measurements of capacitance and permittivity? 4. How can you get minor geometric dimensions of the capacitors and a large capacitance simultaneously? 5. Why do we need to use capacitors in electric circuits? 6. What purposes are series and parallel connection of the capacitors applied? Answers Executed by the student: Group _ First name 7

18 Last name Approved by the teacher: Date 8

19 eport on Laboratory Experiment No 4 Determination of High Value esistance and apacitance with the Help of elaxed Oscillations The student: Group _ First name Last name is allowed to do the laboratory work. Date Purpose of Work capacitance measurement of two capacitors, capacitance of capacitors in series and parallel connection. Do measurement for the resistance of two resistors analogous way. Theoretical ontents. Summary elaxed oscillations are The capacitor voltage-time dependence is shown in Fig.. The table of symbols: t t _ U U q The principle of operation of the relaxed oscillation generator is consist in Fig.. According to the second Kirchhoft law U 0 I U c, where U 0 - ig 9

20 I -, -, U c - alculation Formulas T T ( const ), where T T T T ( const ), where T T Electric Scheme G. D. T U - 0 Measurements results Table. Electric circuit parameters The order of experiment The numbers of flashes, n t [sec] T [sec] T [sec] Unknown quantity X X; X ; X XP XP ; XS 0

21 XS ; Electric circuit parameters The order of experiment The numbers of flashes, n t [sec] T [sec] T [sec] Table. Unknown quantity X X; X ; X XP XP ; XS ; XS Measured by the student: Verified by the teacher: Name Analysis of Measurements alculate ratio and absolute errors of only one series of measurement on teacher s option. Formula for the error calculation: X X

22 X X Note: Values of and are defined with the ratio equaling error 0%. Measurement's result: X X X esume Test Questions 7. an you explain the principle of operation of the relaxed oscillation s generator? U 0 U ig 8. Get formula T ln. U 0 U q 9. What oscillations are called relaxed? 0. Formulate the second Kirchhoff s law.. Write down the differential equation of changing capacitor s charge. Answers Executed by the student: Group First name Last name

23 Approved by the teacher: Date eport on Laboratory Experiment No 5 Study of Semiconductor esistance-temperature Dependence. Determination of Activation Energy The student: Group _ First name Last name is allowed to do the laboratory work. Date Purpose of work Get the voltage-current characteristic and temperature-resistance dependence of a semiconductor. Define the activation energy for the given semiconductor. Devices and Instruments Semiconductor resistor (theristor), vessel with water, potentiometer, direct current sources, voltmeter, microammeter, switch and wires. Theoretical contents. Summary An activation energy of a semiconductor is Two type of semiconductors exist in nature: n-type and p-type. These are schematically shown in Fig.. 3

24 Fig.. The role of impurity in semiconductor of n-type is The role of impurity in semiconductor of p-type is On the empirical diagram: E c E E V a Table of symbols _ E d _ E E a E d The resistance of semiconductor decreases with the increasing of its temperature: where, 0 E _ k T The n - dependence looks like T From this dependence it is possible to determine the value of alculation Formulas U I E k tg Where, U I k tg E Electric Scheme 4

25 where, P V T A Sw esults U (Volt ) I (Ampere) Table. t O T O K, K T I (Ampere) U (Volt ) (Ohm) Table. n Measured by the student: Verified by the teacher: Name Analysis. Let's plot the graph of voltage-current characteristic using the data from Table at the room temperature. I f (U) I (A) 5

26 onclusions. Let's plot the graph of temperature-resistance dependence using the data from Table. f (T) onclusion: T 0 K 3. Let's plot the graph n f ( ) using the data from Table. T n onclusion: 6

27 tg is found from the graph: tg eference data: 3 k,380 Joule oulomb ; ev,6 0 9 Joule ; Е k tg ; E esume Test Questions. What properties subdivide solids into dielectrics, conductors and semiconductors?. What value is called the activation energy of conductivity? 3. How does the resistance of semiconductor change with temperature? Why? 4. What semiconductor is called a semiconductor of p-type? 5. What semiconductor is called a semiconductor of n-type? Answers Executed by the student: 7

28 Group First name_ Last name_ Approved by the teacher: Date eport on Laboratory Experiment No 6 Measurement of Magnetic Field of a Solenoid The student: Group _ First name Last name is allowed to do the laboratory work. Date Purpose of Work Determination of the magnetic induction and magnetic field strength inside a solenoid at the given points along it's axis. Determination of the magnetic induction dependence on the current, passing through the turns of the solenoid. Devices and Instruments Solenoid, millivoltmeter, measuring coil, rheostat and connecting wires. Theoretical ontents. Summary A solenoid is The magnetic induction is The magnetic field strength is 8

29 Method of magnetic induction measurement consists in _ Electric ircuit of the Experimental Plant Table of symbols: А - _ L - _ S - _ Sw - - _ b - alculation Formulas 3. The magnetic induction: B where, S N 4. Magnetic field strength: H where, 0 esults of Measurements and alculations I (Ampere) (Volt ) B (tesla ) H ( Ampere / m) Table.,5,5 3 3,5 4 9

30 I (Ampere) I (ampere) Table. x (cm) (Volt ) B (tesla ) H ( Ampere / m) x (cm) (volt) B (tesla ) H ( ampere / m) Measured by the student: Verified by the teacher: Name Analysis of Measurements. Plot the graphical dependence using the data from Table. а) B f (I) ; 30

31 . Plot the graphical dependence using the data from Table. b) B f (x) 3. alculate B using the data of measurements and Biot-Savart-Laplace law at three points on the solenoid's axis (the current strength is given by the teacher). At the center point On the end side of solenoid B B 3

32 Outside of solenoid B 4. ompare experimental data of B и H with the results of calculation at equal strengths of current. 5. Estimate the accuracy of measurements using an accuracy grade of devices. I ( accuracy. grade) 0 I N ( accuracy. grade) 0 U N esume Test Questions. What is the difference between the magnetic induction and magnetic field strength?. How does an induction depend on the magnetic strength? 3. What magnetic field is called uniform? 4. How does an induction in the central point change if the length of a solenoid is decreased? 5. What phenomenon is called an electromagnetic induction? How is it used in this laboratory work? Answers 3

33 Executed by the student: Group First name Last name Approved by the teacher: Date 33