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Question-1. what is importance of colours coding resistor?
Answer-1: The electronic color code is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables
Question-2. why we use Resistance?
Answer-2: To protect circuit from high value of current.
Question-3. If voltage & current given then how we calculate the value of resistance?
Answer-3: R = V/I
Question-4. what is common between inductor & resistor?
Answer-4: inductor is a passive device & resistor is a passive device.
Question-5. what is resistor?
Answer-5: A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current through it in accordance with Ohm's law: V = IR
Question-6. How parallel connection is done in resistor?
Answer-6: To find their total equivalent resistance (Req):
1/Req = 1/R1 + 1/R2 + 1/R3 + .... + 1/Rn
Question-7. how resistor connected in series?
Answer-7: To find their total resistance (Req):
Req = R1 + R2 + R3 + ...... + Rn
Question-8. Write the equation for power dissipation in resistor?
Answer-8: The power dissipated by a resistor (or the equivalent resistance of a resistor network) is P = I2R = IV = V2/R
Question-9. what are features of carbon composition resistor?
Answer-9: This type is also popular. It?s made from a mixture of carbon powder and glue like binder. To increase the resistance, less carbon is added. These resistors show predictable performance, low inductance, and low capacitance. Power ratings range from about 1/4 to 2 W. Resistances range from 1 Ohm to about 100 MOhm, with tolerances around +/- 5 percent.
Question-10. what are features of foil resistor?
Answer-10: Foil resistors are similar in characteristics to metal film resistors. Their main advantages are better stability and lower temperature coefficient of resistance (TCR). They have excellent frequency response, low TCR, good stability, and are very accurate. They are manufactured by rolling the same wire materials as used in precision wire wound resistors to make thin strips of foil.
This foil is then bonded to a ceramic substrate and etched to produce the value required. They can be trimmed further by abrasive processes, chemical machining, or heat treating to achieve the desired tolerance. Their main disadvantage is that the maximum value is less than metal film resistors. The accuracy is about the same as metal film resistors, the TCR and stability approaches precision wire wounds but are somewhat less because the rolling and packaging processes produce stresses in the foil. The resistive materials used in precision wire wound resistors are very sensitive to stress, which result in instability and higher TCS. Any stresses on these materials will result in a change in the resistance value and TCR, the greater the stresses, the larger the change. This type can be used as strain gauges, strain being measured as a change in the resistance. When used as a strain gauge, the foil is bonded to a flexible substrate that can be mounted on a part where the stress is to be measured.
Question-11. What are wiring codes?
Answer-11: Wires may be color-coded to identify their function, voltage class, polarity, and phase or to identify the circuit in which they are used. The insulation of the wire may be solidly colored, or where more combinations are needed, one or two tracer stripes may be added. Some wiring color codes are set by national regulations, but often a color code is specific to a manufacturer or industry.
Question-12. Explain color coding with example?
Answer-12: For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ?5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms. Resistors manufactured for military use may also include a fifth band which indicates component failure rate reliability.
Question-13. What are transformer codes?
Answer-13: Power transformers used in North American vacuum-tube equipment often were color-coded to identify the leads. Black was the primary connection, red secondary for the B+ (plate voltage), red with a yellow tracer was the center tap for the B+ full-wave rectifier winding, green or brown was the heater voltage for all tubes, yellow was the filament voltage for the rectifier tube (often a different voltage than other tube heaters). Two wires of each color were provided for each circuit, and phasing was not identified by the color code.
Question-14. what does the color bands signify?
Answer-14: It is sometimes not obvious whether a color coded component is a resistor, capacitor, or inductor, and this may be deduced by knowledge of its circuit function, physical shape or by measurement. Resistor values are always coded in ohms (symbol O), capacitors in Pico farads (pF), and inductors in micro henries (?H). To distinguish left from right there is a gap between the C and D bands.
Band A is first significant figure of component value (left side)
Band B is the second significant figure
Band C is the decimal multiplier
Band D if present, indicates tolerance of value in percent (no color means 20%)
Question-15. what is the basic of measuring resistance by multimeter?
Answer-15: The basic idea is that the multimeter places a voltage at the two probes and this will cause a current to flow in the item for which the resistance is being measured. By measuring the resistance it is possible to determine the resistance between the two probes of the multimeter or other item of test equipment.
Question-16. How resistance is measured with help of multimeter?
Answer-16: Measuring resistance with a digital multimeter is easier and faster than making a resistance measurement with an analogue multimeter as there is no need to zero the meter. As the digital multimeter gives a direct reading of the resistance measurement, there is also no equivalent of the reverse reading found on the analogue multimeters.There are a few simple steps required to make a resistance measurement with a digital multimeter:
Select the item to be measured: This may be anything where the resistance needs to be measured and estimate what the resistance may be.
1. Insert the probes into the required sockets often a digital multimeter will have several sockets for the test probes. Insert these or check they are already in the correct sockets. Typically these might be labeled COM for common and the other where the ohms sign is visible. This is normally combined with the voltage measurement socket.
2. Turn on the multimeter
3. Select the required range The digital multimeter needs on and the required range selected. The range selected should be such that the best reading can be obtained. Normally the multimeter function switch will be labeled with the maximum resistance reading. Choose the one where the estimated value of resistance will be under but close to the maximum of the range. In this way the most accurate resistance measurement can be made.
4. Make the measurement with the multimeter ready to make the measurement the probes can be applied to the item that needs to be measured. The range can be adjusted if necessary.
5. Turn off the multimeter once the resistance measurement has been made, the multimeter can be turned off to preserve the batteries. It is also wise to turn the function switch to a high voltage range. In this way if the multimeter is used to again for another type of reading then no damage will be caused if it is inadvertently used without selecting the correct range and function. Digital multimeters are ideal pieces of test equipment for measuring resistance. They are relatively cheap and they offer a high level of accuracy and general performance.
Question-17. Find the value of resistance black, red, green, gold?
Answer-17: 3 x 107 ohms
Question-18. How we can remember the sequence of color?
Answer-18: B.B.ROY of Great Britain has Very Good Wife.
Question-19. what method is used for finding resistance?
Answer-19: By Ohm?s law, .color coding and with multimeter.
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