Fakultat fur Physik und GeowissenschaftenPhysikalisches Grundpraktikum

E01e “Basic Electric Circuits”

Tasks

1. Set up a series circuit consisting of three resistances with different ratings. Apply an appropriatevoltage. Measure voltages and currents. Compare with your predictions.

2. Set up a parallel circuit consisting of three resistances with different ratings. Apply an appropriatevoltage. Measure voltages and currents. Compare with your predictions.

3. Set up a resistance cube consisting of twelve resistances with identical ratings. Determine the totalresistance along a cube edge, a face diagonal or a cube diagonal. Compare with the calculatedvalues for these resistances.

4. Set up a voltage divider and measure the voltage across the second resistance under load. Com-pare with your predictions.

5. Set up a Wheatstone bridge. Apply an appropriate voltage. Measure the bridge voltage as afunction of the resistance value in one of the arms. Compare with your predictions.

Literature

Any physics book on dc circuits should be ok, e.g.Physics for Scientists and Engineers, P. A. Tipler, 3rd Edition, Vol. 2, Chapter 23Physikalisches Praktikum, 14. Auflage, Hrsg. W. Schenk, F. Kremer, Elektrizitatslehre, 1.0.1, 1.0.2, 1.1,1.2, 1.4

Accessories

Voltage supply, circuit board, resistors (100, 200, 1k, 2k, 5.1k, 10k, 20kΩ), resistor decade, two multi-meters

Keywords for preparation

• Kirchhoff’s rules, series and parallel circuits of resistances

• Voltage divider, voltage divider under load

• Wheatstone bridge

• Internal resistance

• Voltage- and current-correct measurements

1

Digital multimeter

1. Front panel

2. Measuring range selector (grey: resistance,blue: DCV direct voltage and ACV ac volta-ge, red: DCA direct current and ACA alter-nating current, yellow: capacitance, frequen-cy, ...)

3. Terminals (COM: common terminal, V /Ωvoltage/resistance against COM, mA: currentfor small current values up to 200 mA, 20A:current for measurements up to 20 A)

The multimeters available in the E01 lab might lookdifferent in design, but will have the same socketlayout and functionality.

Typical accuracy:

DC-Volt 200 mV, 2, 20, 200 V ±(0, 3% + 1 Digit)1000 V ±(0, 5% + 1 Digit)

AC-Volt 200 mV, 2, 20, 200 V ±(2, 5% + 5 Digit)750 V ±(1, 5% + 5 Digit)

DC-Ampere 2 mA ±(0, 5% + 1 Digit)200 mA ±(1, 2% + 1 Digit)20 A ±(2, 0% + 5 Digit)

AC-Ampere 2 mA ±(1, 0% + 3 Digit)200 mA ±(1, 8% + 5 Digit)20 A ±(3, 0% + 5 Digit)

Ohm 200 Ohm, 2, 20, 200 kOhm, 2 MOhm ±(0, 5% + 3 Digit)20 MOhm ±(1, 0% + 2 Digit)

Please put resistors back into the correct compartments of the resistor box !!!

2

Task 1

Circuit

Task 2

Circuit

Please put resistors back into the correct compartments of the resistor box !!!

3

Task 3

During your preparation:

• Devise a way to map a three-dimensional cube consisting of twelve identical resistances R onto atwo-dimensional circuit board.

• Calculate the total resistance of this circuit, when the voltage is applied along a cube edge, a facediagonal or a cube diagonal.

Task 4

Circuit

During your preparation:Calculate the load voltage as a function of load resistance with R1 and R2 treated as fixed parameters.In the experiment, fix the values of R1 < R2 in an appropriate way to obtain the desired voltage

UL in the limit of an unloaded voltage divider (RL → ∞). Then measure UL as a function of RL withRL ≥ (R1 ‖ R2), where (R1 ‖ R2) denotes the resistance of a R1–R2 parallel circuit. Plot U/UL versus1/RL and determine R1 and the ratio R1/R2 from the plot.

Please put resistors back into the correct compartments of the resistor box !!!

4

Task 5

Circuit

During your preparation:Calculate the bridge voltage UB as a a function of the applied voltage U and the resistances R1, R2,

R3 and R4. Consider the case R1 = R3 and R2 = R4. What can this setup be used for?In the experiment, choose resistances R1 = R3 and use a variable resistor in place of R4. Measure

the bridge voltage UB as a function of R4. Plot UB versus R4 and determine R2.

Please put resistors back into the correct compartments of the resistor box !!!

5