# Class 12 Physics MCQ – Current Electricity – Resistivity of Various Materials

This set of Class 12 Physics Chapter 3 Multiple Choice Questions & Answers (MCQs) focuses on “Current Electricity – Resistivity of Various Materials”.

1. Identify the type of materials which have resistivities in the range of 10-8 Ωm to 10-6 Ωm.
a) Semiconductors
b) Insulators
c) Conductors
d) Thyristors

Explanation: Conductors have low resistivities in the range of 10-8 Ωm to 10-6 Ωm. Metals are good conductors. Conductors are objects or types of material that allows the flow of charge in one or more directions, and a result, the resistance offered against the flow of charge will be less.

2. Which of the following is a widely used variety of commercial resistor?
a) Bio amplification resistor
b) Wire-bound resistor
c) Ultrasonic resistor
d) Copper resistor

Explanation: A wire bound resistor is an electrical passive component that limits current. Wire-bound resistors are made by winding the wires of an alloy like manganin on an insulating base. They are relatively insensitive to temperature.

3. Identify the material whose resistivity is more than 1014 Ωm.
a) Bakelite
b) Copper
c) Aluminum
d) Silicon

Explanation: Insulators are materials which do not conduct electric current, and thereby, offer high resistance to the flow of charges. Insulators like bakelite and hard rubber have very high resistivities in the range of 1014 to 1016 Ωm.

4. Identify the wrong statement describing the color code for carbon resistors.
a) The first band indicates the first significant figure
b) The second band indicates the second significant figure
c) The third band indicates the third significant figure
d) The fourth band indicates the possible variation in the percent of the indicated value

Explanation: The third band indicates the power of ten with which the first and second significant figures must be multiplied to get the resistance value in ohms. All the other statements are valid.

5. Find the resistance value of the carbon resistor if the colors of the four bands are red, red, red and silver respectively.
a) 33 × 102Ω ± 20%
b) 22 × 102Ω ± 5%
c) 22 × 102Ω ± 10%
d) 33 × 103Ω ± 10%

Explanation: A color code is used to indicate the resistance value of a carbon resistor and its percentage accuracy. The corresponding value of resistance for the given color code is 22 × 102 Ω ± 10% (Red-2; Red-2; Red-2; Silver-10%).

6. If the fourth band of the carbon resistor is absent, it implies there is no tolerance.
a) True
b) False

Explanation: The fourth band indicates the tolerance or possible variation in the percent of the indicated value. If the fourth band is absent, it implies the tolerance of the resistor is ±20%.

7. ‘X’ is a type of commercial resistor made from a mixture of clay, carbon black, and resin binder which are pressed and then molded into cylindrical rods by heating. Identify X.
a) Wire-bound resistors
b) Carbon resistors
c) Metal film resistors
d) Surface-mount resistors

Explanation: Carbon resistors are made from a mixture of carbon black, clay and resin binder which are pressed and then molded into cylindrical rods by heating. The rods are enclosed in a ceramic or plastic jacket. They are used in circuits of radio receivers, amplifiers, etc.

8. Find the resistance value of the carbon resistor if the colors of the four bands are yellow, violet, brown and gold respectively.
a) 47 × 101Ω ± 5%
b) 47 × 100Ω ± 5%
c) 47 × 106Ω ± 5%
d) 47 × 102Ω ± 5%

Explanation: A color code is used to indicate the resistance value of a carbon resistor and its percentage accuracy. The corresponding value of resistance for the given color code is 47 × 101Ω ± 5% (Yellow-4; Violet-7; Brown-1; Gold-5%).

9. Find the resistance value of the carbon resistor if the colors of bands are green, violet, and red respectively.
a) 57 × 102Ω ± 5%
b) 57 × 102Ω ± 10%
c) 57 × 102Ω ± 20%
d) 57 × 102Ω

Explanation: A color code is used to indicate the resistance value of a carbon resistor and its percentage accuracy. The corresponding value of resistance for the given color code is 57 × 102Ω ± 20% (Green-5; Violet-7; Red-2; No fourth band-20%).

10. Identify the material whose resistivity lie between 10-6 Ωm and 104 Ωm.
a) Silver
b) Mica
c) Copper
d) Silicon

Explanation: The resistivities of semiconductors lie between 10-6 Ωm and 104 Ωm. A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic aluminum, and an insulator, such as wood. Silicon and germanium are typical semiconductors.

Sanfoundry Global Education & Learning Series – Physics – Class 12.

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