EXPERIMENT 2 Laboratory Components (Resistors)

Transcription

1 Đzmir University of Economics ETE 00 Introduction to Electronics and Communications Engineering EXPERIMENT 2 Laboratory Components (Resistors) A. Background Different resistor structures has been developed to meet different system specifications. For different power dissipation ranges, resistors of differerent materials are producedd as shown in Fig When an application requires a resistor of 1 Watt power rating, possibly a wire wound resistor is chosen (Fig. 1.1a). Fig. 1.1(b) shows 1W metal film resistor. In Fig.1.1(c) and (d), carbon composition resistors of ½ W and ¼ W are shown. For low power applications on the printed circuit boards, surface mount resistors may be used during production as shown in Fig.1.1(e). When a circuit requires resistor of equal resistances, single-in-line package (SIP) resistors of Fig.1.1(f) may be used as shown in. (a) W Wire Wound Resitor (b) 1W Metal Film Resistor (c) ½ W Carbon Composition Resistor (d) ¼ W Carbon Composition Resistor Surface Mount (e) Surface Mount Resistors (f) Single-in-Linee Package (SIP) Resistors Fig Resistors of Different Type The value of a resistor is usually indicated by 4 color band over the resistor as shown in Fig. 1.2(a). 1-1

2 Tolerance Multiplier 2nd Digit 1stDigit Gold (5%) Silver (%) No color (a) (b) Fig Resistor Color Codes (4 band) (c) The first band indicates 1st digit, second band is for 2nd digit and the third band indicates the multiplier. The numerical values corresponding to the color bands are listed in Fig.1.2(b). Since the first color band is brown (1) and the second band is black (0), the first two digits of the are. The multiplier color band being red (2) means the number of zeros added will be 2. So the value of the resistor given in Fig. 1.2(a) is determined as: 1 st Digit Color Brown Value 1 2 nd Digit Multiplier Code Black Resistance 1 Hence above resistor has a value of 1. The above resistorr has a tolerance color of gold; which means error (tolerance) in the resistance value is ±5%. If the tolerance band color is silver, than it means the tolerance in the resistance value is ±%. No color means ±20% tolerance. (a) Tolerance Multiplier 3 rd Digit 2 nd Digit 1 st Digit (b) Fig Resistor Color Codes (5 band) Gold (5%) Silver (%) No color (c) 1-2

3 The color band scheme for 5-color bands is given in Fig For the resistor given in Fig. 1.3.(a), first color band is brown (1), the second band is black (0), and the third band is black (0), so the first three digits are 0. The multiplier color band being red (2) means the number of zeros added will be 2. So the value of the resistor given in Fig. 1.2(a) is determined as: 1 st Digit 2 nd Digit Multiplier Code Resistance Color Brown Black Black 2 Value The above resistance has a tolerance color of gold; which means tolerance is ±5%. The resistance values for each tolerance band is fixed. The nominal values for the first two digits used in each tolerance band are listed in Table Table A.1. Nominal Resistance Values ±5% ±% ±20% Therefore a resistance of value of 1.1 can be found in 5% tolerance range. If such a resistor is required and if ±% resistors are available, the suitable choices may be 1 or 1.2 resistances

4 B. Practical Work 1. Find the resistancee values of the resistors given in Fig.1.4 Resistance Value Tolerance Fig Resistors 2. Color the resistance color bands of the resistors given in Fig.1.5. (a) 120 Ω (± ±%) (b) 4.3 Ω (±5%) (c) 68 (± ±20%) (d) 1.2 MΩΩ (±%) Fig Resistors 3. Color the resistance color bands of the resistors given in Fig.1.6. (e) 120 Ω (± ±%) (f) 4.3 Ω (±5%) (g) 68 (± ±20%) (h) 1.2 MΩΩ (±%) Fig Resistors 1-4

5 4. Calculate the equivalent resistances of the resistor combinations given in Fig (a) (b) = = (c) (d) = = Fig Series and Paraller Conected Resistors 1-5

6 C. Experimental Work C. 1. Determine and measure the values of R1-R2-R3-R4 resistors and write them to Table C.1. given below. Table C.1 Resistor Color Code Multimeter Reading R1 R2 R3 Difference Error (%) R4 C. 2. Explain the differences between the color codes and the measured values. Are they consistent the tolerance specifications of the resistors? C. 3. Build the given circuit onto the boards. Req I1 VS 12 V R1= K I2 R2 K R3 K R4 K R5 K I4 Fig Series and Paraller Conected Resistors 1-6

7 C. 4. Do the following measurements. (Express with the units) Table C.2 Currents Multimeter Reading I 1 I 2 I 4 C. 5. How can you determine the equivalent resistor Req? C. 6. Measure the voltages over each resistor. Determine also the power dissipated ower each resistor. Table C.3 Resistor Voltage Current Power Dissipation R 1 R 2 R 3 R 4 R 5 C. 7. Calculate the power delivered to the circuit using V S =.., I 1 = and P S = V S I 1 =. C. 8. Can you verify the power conservation principle Total Power delivered = Total Power Consumed 1-7