EEE 201 CIRCUIT THEORY I EXPERIMENT 3

Transcription

1 EEE 0 CIRCUIT THEORY I OLTAGE DIIDER 3. Objectives: oltage Divider in No-load Operation: Measurement of the voltage ratios on a voltage divider in no-load operation. oltage divider Formula. oltage Divider Under Load: Measurement of voltage ratios on a voltage divider under load.. 3. Equipment and Materials The list of equipment and materials used in this experiment is shown in Table 3.. Please record any damage, if exists any while performing the experiment, and its way of occurrence in the allocated space of this table in detail. You can also write the difficulties you are confronted with when using the equipment, and your suggestions and critics related with the equipment you used. Table 3. Equipment and material list used in Experiment 3. No: Equipment Model Serial No: Office Stock No: Plug in Board, DIN A4 47 Ω Resistor (W), (5%) 3 00 Ω Resistor (W), (5%) 4 50 Ω Resistor (W), (5%) 5 kω Resistor (W), (5%) 6 Potentiometer 00 Ω, (3W) 7 Multimeters GMBH 8 Stabilized mains power supply unit 0 to +/- 5 9 Connecting Probes and Cables Record of damage or other comments: 3.3 Preliminary Work

2 EEE 0 CIRCUIT THEORY I 3.4 Experimental Procedure and Records 3.4. oltage Divider in No-load Operation i) Assemble the circuit as shown in Fig. 3. R =50 Ω, R =47 Ω.Make sure that the polarities of the voltage source and the measurement instruments are correct, and that the correct measurement ranges have been selected. ii) Set the input voltage E to 0. Measure the component voltages and and record these in Table 3.. iii) Repeat the measurements with R =00 Ω and R =00 Ω. iv) Repeat the measurements with R =47 Ω and R =50 Ω. v) Now assemble the circuit as in Fig. 3.. Measure the component voltages and for 7 different potentiometer settings and record these in Table 3.3. Figure 3. Measurement of the component voltages on a voltage divider. Table 3. Data for Experiment 3.4. R (Ω) R (Ω) (Ω) (Ω) R / R /

3 EEE 0 CIRCUIT THEORY I Figure 3. Measurement of component voltages on a voltage divider consisting of a potentiometer. Potentiometer alues (Settings) a (0) b () c () d (3) e (4) f (5) g (6) Table 3.3 ( ) ( ) vi) Plot the measured results listed in Table 3. on Figure 3.3. vii) Plot the measured results listed in Table 3.3 on Figure

4 EEE 0 CIRCUIT THEORY I Figure 3.3 oltage / resistance graph of a divider consisting of two resistors for various resistance combinations. Figure 3.4 oltage / resistance graph of a voltage divider consisting of a potentiometer, for various potentiometer settings oltage Divider Under Load i) Assemble circuit as shown in Figure 3.5. But, without load resistor R L Take care that the polarity of the power supply and multimeters is correct, and that the correct measurement range has been selected. ii) Set the input voltage E to 0. Measure the component voltages and for 7 different potentiometer settings and record these measurements in Table 3.4. Each time adjust the input voltage to 0. iii) Repeat the measurements with a load resistor R L = kω. iv) Repeat the measurements with a load resistor R L =50 Ω. v) Repeat the measurements with a load resistor R L =47 Ω.. vi) Plot the relationship between the voltage as measured at the potentiometer and the potentiometer setting P for the constant load resistor R L to Figure

5 EEE 0 CIRCUIT THEORY I Figure 3.5 Measurement of component voltage ratios on a voltage divider under load. Table 3.4 Data for the Experiment 3.4. R L = R L = kω () () () () a (0) a (0) b () b () c () c () d (3) d (3) e (4) e (4) f (5) f (5) g (6) g (6) R L = 50 Ω R L = 47 Ω () () () () a (0) a (0) b () b () c () c () d (3) d (3) e (4) e (4) f (5) f (5) g (6) g (6) 5

6 EEE 0 CIRCUIT THEORY I Figure 3.6 Setting characteristics of a voltage divider under load at various load resistance values vii) A potentiometer consists of a fixed resistor, on which any intermediate value may be chosen using a sliding contact. In Fig. 3.7, A and B represents its fixed terminals, C represents the sliding contact terminal. Set the potentiometer as follows: Resistance between A and B : 00 Ω Resistance between A and C : 0 Ω Resistance between C and B : 80 Ω These are nominal values, experimentally choose the values near to these. Then place a load resistor of 47 Ω between C and B, creating the resistor combination shown in Figure

7 EEE 0 CIRCUIT THEORY I viii) How high is the voltage between C and B if a voltage of 0 is applied between A and B? =... BA Figure 3.7 Example for calculating oltage Divider Under Load 3.5 Results and Discussions ) Answer the following questions by using the data of Experiment i) Add voltages and and enter the result in Table 3.. ii) What is the relationship between the total voltage E and the component voltages and? iii) Determine the quotients R R and and enter them in Table 3.. iv) How do the resistance values relate to the corresponding voltages? 7

8 EEE 0 CIRCUIT THEORY I Deduction of the voltage divider formula: R E = + and = using these formulas together with the input voltage E and R = R R + the known resistance ratio, it is possible to calculate the resulting voltage as follows; E (This so-called voltage divider formula is only valid for voltage dividers in no-load operation.) Deductions: = + () E R = () R Thus it follows from () that: = E (3) Applying (3) in () results in: R E E E = = = R Solutions for results in: R + R E = = R R E + R = E R R + 8