Carbon Resistor Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. If the colors of the four bands are orange, orange, orange, and silver, respectively, then what will be the resistance value of the carbon resistor?

1. 33 x 10³ ± 10% Ω
2. 23 x 10³ ± 10% Ω
3. 33 x 10³ ± 20% Ω
4. 33 x 10⁴ ± 10% Ω

Ans. The correct answer is a. 33 x 10³ ± 10% Ω

Explanation: The color and its respective codes are mentioned below

• Organe: 3 (1st digit)
• Organe: 3 (2nd digit)
• Organe: 10³ (Multiplier)
• Silver: 10% (Tolerance)

Hence, the effective resistance is

R = 33 x 10³ ± 10% Ω

Ques. A carbon resistor of resistance 47 x 10³ ± 10% Ω is to be marked with rings of different colors for its identification. The color code sequence will be

1. Yellow, Violet, Orange, and Silver
2. Yellow, Green, Orange, and Silver
3. Green, Violet, Red, and Silver
4. Green, Violet, Red, and Gold

Ans. The correct answer is a. Yellow, Violet, Orange, and Silver

Explanation: The significant digits of resistance and its color code are given as

• 4: Yellow (1st digit)
• 7: Violet (2nd digit)
• 10³: Orange (Multiplier)
• 10%: Silver (Tolerance)

Hence the color code sequence will be

Yellow, Violet, Orange, and Silver.

Ques. Which among the following resistors is the most commonly used variety of commercial resistors?

1. Bio amplification resistor
2. Aluminum resistor
3. Ultrasonic resistor
4. Wire-wound resistor

Ans. The correct answer is d. Wire-wound resistor

Explanation: Wire-wound resistor is a passive electrical component made by winding the wires of an insulating base. They are used to resistor the current to a specific amount. Wire-wound resistors are commonly used commercial resistors.

Ques. Which among the following materials has a resistivity greater than 1014 Ω-m?

1. Aluminium
2. Bakelite
3. Silicon
4. Copper

Ans. The correct answer is b. Bakelite

Explanation: Bakelite is a polymer made up of the monomers phenol and formaldehyde. The resistivity of bakelite is about 1014 Ω-m to 1016 Ω-m.

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Short Answers Questions [2 Marks Questions]

Ques. What is a carbon resistor?

Ans. A carbon resistor, also known as a carbon composition resistor is a fixed resistor that opposes the flow of electric current. They are made from a solid cylindrical resistor element with embedded wire leads or metal end caps. They come in different sizes with power dissipation limits from 1 watt down to 1/8 watt.

Ques. What are the different parts of the carbon resistor?

Ans. The different parts of the carbon resistor are

• Ceramic Core
• Carbon Film
• Nickel Cap
• Lead
• Protective Lacquer

Ques. A carbon resistor of resistance 34 x 10³ ± 5% Ω is to be marked with rings of different colors for its identification. What will be the color code sequence?

Ans. The significant digits of resistance and its color code are given as

• 3: Orange (1st digit)
• 4: Yellow (2nd digit)
• 10³: Orange (Multiplier)
• 5%: Gold (Tolerance)

Hence the color code sequence will be

Orange, yellow, Orange, and Gold.

Ques. What are the applications of carbon resistors?

Ans. The applications of carbon resistors are

• Carbon resistors are capable of withstanding high-energy pulses.
• It is used in surge and discharge protection of electrical circuits.
• It is used in high-frequency applications.
• It is used in the current limiting circuit.
• It is used in power control circuits.

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Long Answers Questions [3 Marks Questions]

Ques. What are the factors affecting the resistance of carbon resistors?

Ans. The following are the factors affecting the resistance of carbon resistors

• The resistance of a carbon resistor depends on the length of a solid cylindrical rod. 
• Resistance of carbon composition resistors is inversely proportional to the amount of carbon added.
• Resistance of carbon composition resistors is inversely proportional to the cross-sectional area of the cylindrical rod.

Ques. A voltage of 5 V is applied across a color-coded carbon resistor with first, second, and third rings of brown, black, and red color. What is the current flowing through the resistor?

Ans. The color and its respective codes are mentioned below

• Brown: 1 (1st digit)
• Black: 0 (2nd digit)
• Red: 10² (Multiplier)

Hence, effective resistance is

R = 10 x 10² = 1000 Ω

According to Ohm’s law

The current flowing through the resistor is given by

I = V/R = 5/1000 = 5 x 10^-3 A = 5 mA

Ques. What are the advantages of carbon resistors?

Ans. The following are the advantages of carbon resistors

• It has the ability to withstand high-energy pulses.
• Carbon resistors are cheaper than wire wound resistors.
• It is available in a long range of resistance values making flexibility in designing circuits.
• It is capable of handling high-power dissipation.
• Color coding of carbon resistors makes it easier to identify the specific values of resistance.

Ques. What are the disadvantages of carbon resistors?

Ans. The following are the disadvantages of carbon resistors

• The noise generated by carbon resistors is more than any other type of resistor due to the mixture of different materials.
• They have a large negative coefficient of resistance that causes the resistance to change rapidly when the temperature changes.
• They are highly sensitive to humidity.
• Accuracy is low
• Poor stability

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the differences between carbon resistors and wire-wound resistors?

Ans. The differences between carbon resistors and wire-wound resistors are

Ques. What are thermistors? Write its applications.

Ans. Thermistors are highly temperature depended resistors usually made up of the oxides of various metals like copper, iron, nickel, cobalt, and also of semiconductor materials.

A thermistor has a very high-temperature coefficient of resistivity.

Some applications of thermistors are

• They are used in electronic circuits for checking and controlling the variation in voltage.
• They are used in the protective circuit of electrical equipment like transformers, motors, and generators.
• They are used in industries in temperature control units.

Ques. Suppose the color band sequence of a resistor is green, brown, yellow, and gold. What is the effective resistance of the resistor?

Ans. The color and its respective codes are mentioned below

• Green: 5 (1st digit)
• Brown: 1 (2nd digit)
• Yellow: 10⁴ (Multiplier)
• Gold: ± 5% (Tolerance)

Hence, effective resistance is

R = 51 x 10⁴ ± 5%

⇒ R = 51 x 10⁴ ± [51 x 10⁴ x 5/100]

⇒ R = 51 x 10⁴ ± (2.55 x 10⁴)

⇒ R = (51 ± 2.55) x 10⁴ Ω

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