A LABORATORY MANUAL OF PHYSICS AND APPLIED ELECTRICITY
CONTENTS COMMONLY USED LABARATORY EQUIPMENTES INTRODUCTION DIGITAL MULTI METER (DMM) FUNCTION GENERATOR (SIGNAL GENERATOR) OSCILLOSCOPE POWER SUPPLY BREADBOARD REFERENCE FOR FURTHER STUDY RESISTORS TOLERANCE OF RESISTORS PROCEDURE MEASUREMENT OF LOW RESISTANCES MEASUREMENT OF VERY LOW RESISTANCES SERIES AND PARALLEL CONNECTION OF RESISTORS OHM’S LAW POTENTIOMETER LIGHT DEPENDENT RESISTOR (LDR) THERMISTOR OBSERVING THE CURRENT WAVEFORM DIGITAL MULTI METER INTERNAL RESISTANCE OF DMM IN VOLTAGE MEASUREMENT MODE INTERNAL RESISTANCE OF DMM IN CURRENT MEASUREMENT MODE TEST CURRENT OF DMM IN RESISTANCE MEASUREMENT MODE DC COMPONENT (AVERAGE VALUE) MEASUREMENT WITH DMM RMS MEASUREMENT WITH DMM TRUE RMS DMM’S FREQUENCY RESPONSE OF THE AC VOLTMETER AND AC AMMETER CIRCUIT THEOREMS VOLTAGE DIVISION, CURRENT DIVISION AND KCL NODAL ANALYSIS MESH ANALYSIS THEVENIN THEOREM MAXIMUM POWER TRANSFER REFERENCES FOR FURTHER STUDY FIRST ORDER AND SECOND ORDER CIRCUITS OUTPUT RESISTANCE OF FUNCTION GENERATOR STEP RESPONSE OF RC CIRCUIT STEP RESPONSE OF RL CIRCUIT STEP RESPONSE OF SERIES RLC CIRCUIT STEP RESPONSE OF PARALLEL RLC CIRCUIT STEADY STATE DC AND AC ANALYSIS AND FILTERS STEADY STATE DC ANALYSIS STEADY STATE AC (SINUSOIDAL) ANALYSIS SERIES AND PARALLEL RESONANCE LOW-PASS FILTER HIGH-PASS FILTER MAGNETIC COUPLING AND TRANSFORMERS DOT CONVENTION IN TRANSFORMERS TURN RATIO OF TRANSFORMER COUPLING COEF?CIENT OF MUTUALLY COUPLED INDUCTORS DIGITAL MULTI METER (DMM) DIGITAL MULTIMETERS ARE MEASURING INSTRUMENTS THAT CAN MEASURE QUANTITIES SUCH AS VOLTAGE, CURRENT, AND RESISTANCE MEASURED VALUES ARE SHOWN ON A DIGITAL DISPLAY, ALLOWING THEM TO BE READ EASILY AND DIRECTLY, EVEN BY ?RST-TIME USERS STUDY THE USER MANUAL OF THE DMM THAT YOU WILL USE IN THE EXPERIMENTS ENSURE THAT YOU ARE ABLE TO DO THE FOLLOWINGS: (A) MEASUREMENT OF RESISTANCE (B) MEASUREMENT OF AC/DC VOLTAGES (C) MEASUREMENT OF AC/DC CURRENTS IN THE RANGE OF AMPS (D) MEASUREMENT OF AC/DC CURRENTS IN THE RANGE OF MILLI/MICRO AMPS ASK YOUR LABORATORY INSTRUCTOR TO MAKE AN EXPLANATION TO YOU IF YOU ARE NOT ABLE TO DO ONE OR MORE OF THE ABOVE TASKS FIG 1 2 SIMPLE MODEL FOR SIGNAL GENERATOR STUDY THE USER MANUAL OF THE FUNCTION GENERATOR THAT YOU WILL USE IN THE EXPERIMENTS ENSURE THAT YOU ARE ABLE TO DO THE FOLLOWINGS: (A) GENERATION OF A SINUSOIDAL SIGNAL WITH AMPLITUDE OF 5 V AND FREQUENCY OF 50 HZ, I E , V(T) = 5 × SIN(2? × 50 × T)V (B) GENERATION OF A SINUSOIDAL SIGNAL WITH AMPLITUDE OF 5 V, FREQUENCY OF 50 HZ AND AVERAGE VALUE OF 3 V, I E , V(T) = 3 + 5 × SIN(2? × 50 × T)V (C) GENERATION OF A SINUSOIDAL SIGNAL WITH PEAK VALUE OF 50 MV, I E , V(T) = 0 05 × SIN(2? × 50 × T)V (D) GENERATION OF A TRIANGULAR WAVE WITH FREQUENCY OF 50 HZ AND PEAK VALUE OF 5 V (FIG 1 3) FIG 1 3 SAMPLE TRIANGULAR WAVE (E) GENERATION OF A PULSE WITH FREQUENCY OF 50 HZ AND DUTY CYCLE OF 25% (FIG 1 4) ASK YOUR LABORATORY INSTRUCTOR TO MAKE AN EXPLANATION TO YOU IF YOU ARE NOT ABLE TO DO ONE OR MORE OF THE ABOVE TASKS BREADBOARD A BREADBOARD IS USED TO BUILD AND TEST CIRCUITS QUICKLY THE BREADBOARD HAS MANY HOLES INTO WHICH CIRCUIT COMPONENTS LIKE ICS AND RESISTORS CAN BE INSERTED A TYPICAL BREADBOARD IS SHOWN IN FIG 1 6 FIG 1 7 CONNECTIONS OF BREADBOARD FIG 1 8 INSIDE OF A BREADBOARD LET’S STUDY AN EXAMPLE ASSUME THAT WANT TO MAKE THE CIRCUIT SHOWN IN FIG 1 9 ON BREADBOARD PUT THE RESISTOR R2 (FIG 1 11) FIG 1 11 RESISTOR R2 IS ADDED PUT THE CAPACITOR C1 (FIG 1 12) FIG 1 13 RESISTOR R3 IS ADDED CONNECT THE RESISTOR R1 TO THE POSITIVE VOLTAGE RAIL AND R2 AND R3 TO THE NEGATIVE VOLTAGE RAIL (FIG 1 14) MEASUREMENT WITH CELL PHONE YOU CAN CONVERT YOUR CELL PHONE, TABLET OR EVEN YOUR SMART WATCH INTO A DIGITAL MULTIMETER, DIGITAL STORAGE OSCILLOSCOPE (DSO) OR A LOGGER WITH THE AID OF POKIT METER (FIGS 1 16 AND 1 17) OR POKIT PRO (FIG 1 18) MORE INFORMATION CAN BE FOUND ON HTTPS://WWW POKITINNO VATIONS COM/ FIG 1 16 POKIT METER FIG 1 17 POKIT METER COMMONLY USED LABARATORY EQUIPMENTES FIG 1 18 POKIT PRO REFERENCE FOR FURTHER STUDY 1 ASADI F , EGUCHI K , ELECTRONIC MEASUREMENT: A PRACTICAL APPROACH, SPRINGER, INTRODUCTION ANY COMPONENT USED IN A CIRCUIT HAS A TOLERANCE THE TOLERANCE OF A COMPONENT IS A MEASURE OF ACCURACY AND INDICATES HOW MUCH THE MEASURED ACTUAL VALUE IS DIFFERENT FROM ITS NOMINAL EXPECTED VALUE FOR INSTANCE, A RESISTOR WITH NOMINAL VALUE OF 1 K AND TOLERANCE OF 5% MAY HAVE ANY VALUE BETWEEN 1 K×0 95 = 0 95 K AND 1 K×1 05 = 1 05 K IN THIS EXPERIMENT WE WILL STUDY THE TOLERANCE OF RESISTORS LET’S SEE HOW VALUE OF A RESISTOR IS READ IN BIG BULKY RESISTORS THERE IS ENOUGH SPACE TO WRITE THE NOMINAL VALUE AND TOLERANCE CODE USING NUMBERS AND ALPHABET LETTERS FOR INSTANCE, THE RESISTOR SHOWN IN FIG 2 1 HAS NOMINAL VALUE OF 0 47 AND IS CAPABLE TO DISSIPATE 5 W OF HEAT THEREFORE, MAXIMUM VALUE OF 3 26 A CAN PASS THROUGH THE RESISTOR ACCORDING TO TABLE 2 1, LETTER J SHOWS THAT THIS RESISTOR HAS TOLERANCE OF 5% THEREFORE, ACTUAL VALUE OF THE RESISTOR MAY BE BETWEEN 0 95×0 47 = 0 45 AND 1 05×0 47 = 0 49 TABLE 2 2 DIGITS ASSOCIATED WITH COLORS COLOR DIGIT ASSOCIATED WITH THE COLOR BLACK BROWN RED ORANGE YELLOW GREEN BLUE VIOLET GREY WHITE IN RESISTORS WITH 4 COLOR BANDS, ?RST AND SECOND COLOR BANDS SHOW THE ?RST AND SECOND DIGITS AND THIRD COLOR BAND SHOWS THE MULTIPLIER FOURTH COLOR BAND SHOWS THE TOLERANCE AND USUALLY TAKES THE COLORS SHOWN IN TABLE 2 3 FOR INSTANCE, ASSUME THAT THIRD BAND IS GREEN IN THIS CASE ?RST TWO DIGITS MUST BE MULTIPLIED WITH 105 = 100000 NOTE THAT WHEN THIRD COLOR IS GOLD, THE ?RST TWO DIGITS MUST BE DIVIDED BY 10 TABLE 2 3 TOLERANCE ASSOCIATED WITH COLORS COLOR TOLERANCE ASSOCIATED WITH THE COLOR GOLDEN 5% SILVER 10% FOR INSTANCE, A RESISTOR WITH BROWN–GREEN–RED–GOLD COLOR BANDS SHOWS A 15×100 = 1500 = 1 5 K RESISTOR WITH TOLERANCE OF 5% ACTUAL VALUE OF SUCH A RESISTOR CHANGES FROM 1 5 K×0 95 = 1 43 K TO 1 5 K×1 05 = 1 58 K TABLE 2 4 SHOWS COLOR BANDS OF DIFFERENT RESISTORS IN THIS TABLE, FOR INSTANCE, 5R6 SHOWS 5 6 , 8K2 SHOWS 8 2 K, 330 K SHOWS 330 K, 12 M SHOWS 12 M AND 3M9 SHOWS 3 9 M RESISTORS TABLE 2 4 COLOR BANDS FOR DIFFERENT RESISTORS BAND BAND 82M IN RESISTORS WITH 5 COLOR BANDS, ?RST, SECOND AND THIRD COLOR BANDS SHOW THE ?RST, SECOND AND THIRDS DIGITS AND FOURTH COLOR BAND SHOWS THE MULTIPLIER FIFTH COLOR BAND SHOWS THE TOLERANCE AND USUALLY TAKES THE COLORS SHOWN IN TABLE 2 5 NOTE THAT WHEN FOURTH COLOR IS GOLD, THE ?RST THREE DIGITS MUST BE DIVIDED BY 10 FOR INSTANCE, GREEN–BROWN–BLACK–RED– BROWN (FIG 2 3) SHOWS 51 K WITH TOLERANCE OF 1% FIG 2 3 RESISTOR WITH 5 COLOR BANDS TABLE 2 5 TOLERANCE ASSOCIATED WITH COLORS COLOR TOLERANCE ASSOCIATED WITH THE COLOR (%) BROWN GOLDEN SILVER PROCEDURE PREPARE 100 , 1 K, 10 K AND 100 K RESISTORS WRITE THE COLOR BANDS IN TABLE 2 7 RESISTORS TABLE 2 7 COLOR BANDS OF RESISTORS UNDER TEST NOMINAL VALUE COLOR OF ?RST BAND COLOR OF SECOND BAND COLOR OF THIRD BAND COLOR OF FOURTH BAND (TOLERANCE BAND) 1 K 10 K 100 K FILL THE TABLE 2 8 BASED ON THE TOLERANCE BAND OF THE RESISTORS TABLE 2 8 MAXIMUM AND MINIMUM VALUES OF RESISTORS UNDER TEST NOMINAL VALUE MINIMUM VALUE MAXIMUM VALUE 1 K 10 K 100 K USE A DMM TO MEASURE THE VALUES OF RESISTORS AND WRITE THEM IN THE TABLE 2 9 TABLE 2 9 MEASURED VALUES FOR RESISTORS UNDER TEST NOMINAL VALUE VALUE MEASURED WITH DMM 1 K 10 K 100 K ENSURE THAT MEASURED VALUES LIES BETWEEN THE MINIMUM AND MAXIMUM VALUES OF TABLE 2 8 NOW KEEP A HOT SOLDERING IRON BEHIND THE RESISTORS FOR 30 S AND MEASURE THE RESIS- TANCES AGAIN WRITE THE MEASURED VALUES IN TABLE 2 10 COMPARE THE TABLE 2 10 WITH VALUES MEASURED IN ROOM TEMPERATURE WHAT IS THE EFFECT OF TEMPERATURE INCREASE ON THE RESISTANCE? TABLE 2 10 MEASURED VALUES FOR HEATED RESISTORS NOMINAL VALUE VALUE MEASURED WITH DMM PROCEDURE PREPARE A LOW VALUE RESISTOR FOR INSTANCE, A 2 2 OR 3 3 RESISTOR IS GOOD USE THE TOLERANCE BAND TO CALCULATE THE MINIMUM AND MAXIMUM VALUES OF THE RESISTOR UNDER TEST AND CALL THEM RMIN AND RMAX, RESPECTIVELY NOW CONNECT THE DMM LEADS TO THE RESISTOR UNDER TEST AND MEASURE ITS VALUE (FIG 2 4) CALL THE MEASURED VALUE R1 FIG 2 4 RESISTOR IS CONNECTED TO THE DMM INTRODUCTION YOU CAN USE SERIES AND PARALLEL CONNECTION OF RESISTORS IN ORDER TO MAKE A RESISTOR WHICH IS NOT AVAILABLE IN THE TABLE OF STANDARD RESISTORS SERIES AND PARALLEL CONNECTION OF TWO R1+R2 IF YOU HAVE ACCESS TO RLC METER YOU CAN VERIFY THE FORMULAS FOR SERIES/PARALLEL INDUCTOR/CAPACITORS AS WELL FIG 2 17 MEASUREMENT OF CURRENT AND VOLTAGE OF A RESISTOR CHANGE THE VALUE OF VARIABLE VOLTAGE SOURCE V1 IN FIG 2 17 IN ORDER TO PRODUCE THE CURRENTS SHOWN IN TABLE 2 11 THEN WRITE THE CORRESPONDING VOLTAGE READINGS FOR EACH CURRENT AND CALCULATE THE RESISTANCE USING THE OHM’S LAW FOR EACH ROW THE CALCULATED RESISTANCE IS ALMOST CONSTANT TABLE 2 11 I–V DATA FOR RESISTOR UNDER TEST VALUE READ BY MILLI AMPERE METER (I) VALUE READ BY VOLTMETER (V) R = V I 1 MA 3 MA 5 MA 7 MA 9 MA 11 MA 13 MA 15 MA WHEN CURRENT THROUGH THE RESISTOR IS 15 MA TOUCH THE RESISTOR BODY WITH YOUR ?NGERS THE HEAT THAT YOU SENSE IS THE P = RI 2 ?1K × (15M)2 = 225 MW POWER DISSIPATED IN THE RESISTOR NOW REPLACE THE RESISTOR R1 IN FIG 2 17 WITH A SMALL 12 V CAR LAMP (FIG 2 18) AN AMMETER IS USED TO MEASURE THE CIRCUIT CURRENT (NOTE THAT MILLI AMMETER IS NOT USED) FILL THE TABLE 2 12 IS THE LAMP OBEYING THE OHM’S LAW? IS IT AN OHMIC CONDUCTOR? RESISTORS FIG 2 18 MEASUREMENT OF CURRENT AND VOLTAGE OF A SMALL CAR LAMP TABLE 2 12 I–V DATA FOR LAMP UNDER TEST VALUE READ BY AMPERE METER (I) VALUE READ BY VOLTMETER (V) R = V I FIG 2 19 A REAL POTENTIOMETER AND ITS STRUCTURE FIG 2 20 VOLTAGE DIVIDER MADE WITH POTENTIOMETER YOU CAN MAKE A VARIABLE RESISTOR WITH THE AID OF CONNECTIONS SHOWN IN FIGS 2 21 AND 2 22 FIG 2 21 FIRST METHOD TO MAKE A VARIABLE RESISTOR PROCEDURE PREPARE A 10 K POTENTIOMETER (FIG 2 24) CONNECT THE TERMINAL 1 AND 3 (FIG 2 24) TO A DMM (FIG 2 25) AND WRITE THE SHOWN RESISTANCE COMPARE THIS MEASURED VALUE WITH THE NOMINAL VALUE PRINTED ON THE POTENTIOMETER ROTATE THE POTENTIOMETER SHAFT AND OBSERVE THAT RESISTANCE SHOWN BY THE DMM DOESN’T CHANGE FIG 2 24 LABELS 1–3 ARE GIVEN TO POTENTIOMETER TERMINALS FIG 2 25 MEASUREMENT OF NOMINAL VALUE OF THE POTENTIOMETER CONNECT THE DMM TO PIN 2 AND 3 (FIG 2 26) THEN ROTATE THE POTENTIOMETER SHAFT WRITE THE MAXIMUM AND MINIMUM RESISTANCE VALUES THAT DMM SHOWS FIG 2 26 MEASUREMENT OF RESISTANCE BETWEEN CENTER TERMINAL (WIPER) AND SIDE TERMINAL RESISTORS NOW PREPARE THE CIRCUIT SHOWN IN FIG 2 27 ROTATE THE POTENTIOMETER AND PAY ATTENTION TO VOLTAGE THAT VOLTMETER SHOWS WRITE THE MAXIMUM AND MINIMUM VOLTAGE THAT VOLTMETER SHOWS THE MAXIMUM VOLTAGE IS OBTAINED WHEN THE RESISTANCE BETWEEN TERMINAL 2 AND IS MAXIMUM THE MINIMUM VOLTAGE IS OBTAINED WHEN THE RESISTANCE BETWEEN TERMINAL PROCEDURE CONNECT THE LDR TO THE MULTIMETER IN ORDER TO MEASURE ITS RESISTANCE (FIG 2 30) COVER THE LDR WINDOW WITH YOUR HANDS THIS DECREASES THE AMOUNT OF LIGHT WHICH REACHES TO THE LDR WRITE THE VALUE WHICH IS SHOWN BY THE MULTIMETER NOW USE A ?ASHLIGHT TO SHED LIGHT ONTO THE LDR WINDOW WRITE THE VALUE WHICH IS SHOWN BY THE MULTIMETER AND COMPARE IT WITH THE DARK CASE FIG 2 30 MEASUREMENT OF LDR RESISTANCE IN FIG 2 30 WE USED A DIGITAL MULTIMETER TO MEASURE THE RESISTANCE OF THE LDR NOW WE WILL USE AN INDIRECT METHOD TO MEASURE THE RESISTANCE OF THE LDR MAKE THE CIRCUIT SHOWN IN FIG 2 31 POTENTIAL OF POINT B CHANGES WITH RESPECT TO THE AMOUNT OF LIGHT REACHES TO THE LDR COVER THE LDR WINDOW WITH YOUR HANDS AND MEASURE THE VOLTAGE OF POINT B USE THE RLDR R1+RLDR × V1 = VB ?RLDR = VB V1?VB R1 FORMULA TO CALCULATE THE RESISTANCE OF THE LDR THEN SHED LIGHT ONTO THE LDR WINDOW USING A ?ASHLIGHT AND MEASURE THE VOLTAGE OF POINT B AGAIN CALCULATE THE RESISTANCE OF THE LDR FOR THIS CASE AND COMPARE IT WITH THE PREVIOUS DARK CASE THERE ARE TWO TYPES OF THERMISTORS: NEGATIVE TEMPERATURE COEF?CIENT (NTC) AND POSITIVE TEMPERATURE COEF?CIENT (PTC) WITH AN NTC THERMISTOR, WHEN THE TEMPERA- TURE INCREASES, RESISTANCE DECREASES CONVERSELY, WHEN TEMPERATURE DECREASES, RESISTANCE INCREASES (FIG 2 33) THIS TYPE OF THERMISTOR IS USED THE MOST A PTC THERMISTOR WORKS A LITTLE DIFFERENTLY WHEN TEMPERATURE INCREASES, THE RESISTANCE INCREASES, AND WHEN TEMPERATURE DECREASES, RESISTANCE DECREASES (FIG 2 34) THIS TYPE OF THERMISTOR IS GENERALLY USED AS A FUSE FIG 2 33 BEHAVIOR OF NTC TYPE THERMISTORS FIG 2 34 BEHAVIOR OF PTC TYPE THERMISTORS INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC) AND ANSI SYMBOL FOR PTC AND NTC ARE SHOWN IN FIGS 2 35 AND 2 36, RESPECTIVELY FIG 2 37 CURRENT I IS DRAW BY THE FAN ONE WAY TO CONVERT THE CURRENT SIGNAL INTO VOLTAGE SIGNAL IS TO PUT A SMALL RESISTOR IN SERIES WITH THE LOAD (FIG 2 38) WHEN THE CURRENT PASS THROUGH THE SENSE RESISTOR, IT MAKES THE VOLTAGE DROP VSENSE = RSENSE × I(T) WHICH IS PROPORTIONAL WITH CURRENT PASS THROUGH IT WATTAGE OF THE RSENSE MUST BE BIG ENOUGH TO WITHSTAND THE CURRENT PASS THROUGH IT RSENSE MUST BE SMALL ENOUGH TO AVOID A CONSIDERABLE VOLTAGE DROP ACROSS IT AS WELL THIS CONDITION HELPS US TO ENSURE THAT NEARLY ALL THE INPUT VOLTAGE REACHES THE LOAD ITSELF FIG 2 38 RSENSE ACT AS A CURRENT TO VOLTAGE CONVERTER CONVERSION OF CURRENT SIGNAL INTO VOLTAGE SIGNAL WITH THE AID OF SENSE RESISTOR IS STUDIED IN THIS EXPERIMENT RESISTORS 2 10 2 PROCEDURE MAKE THE CIRCUIT SHOWN IN FIG 2 39 SET THE OSCILLOSCOPE TO SEE THE VOLTAGE WAVEFORM ACROSS THE RSENSE USE OHM’S LAW TO MEASURE THE MAXIMUM CURRENT PASS THROUGH THE FAN FIG 2 39 OBSERVED VOLTAGE IS PROPORTIONAL TO THE CIRCUIT CURRENT NOTE: IF YOU DON’T HAVE ACCESS TO A COMPUTER FAN, YOU CAN USE THE SETUP SHOWN IN FIG 2 40 SIGNAL GENERATOR V1 GENERATES A SINUSOIDAL SIGNAL WITH AMPLITUDE VALUE OF 5 V AND FREQUENCY OF 1 KHZ RO SHOWS THE OUTPUT RESISTANCE OF THE SIGNAL GENERATOR V1 VOLTAGE OBSERVED ON THE OSCILLOSCOPE SCREEN MUST BE DIVIDED BY 4 7 IN ORDER TO OBTAIN THE EQUIVALENT CURRENT FOR EACH INSTANT OF TIME REFERENCE FOR FURTHER STUDY