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Conductivity

📆 October 10, 2024

Conductivity

Total Questions: 26

1. The substance which has a large number of free electrons and offer a low resistance is called: [Uttarakhand P.C.S. (Pre) 2021]

Correct Answer: (c) Conductor
Solution:A conductor, or electrical conductor, is a substance or material that allows electricity to flow through it. In conductive materials, the outer electrons in each atom can easily come or go and are called free electrons. They move easily from atom to atom when voltage is applied. Conductors have a large number of free electrons with low resistance and high thermal conductivity.

2. Which elements is the best conductor of electricity? [Chhattisgarh P.C.S. (Pre) 2011 M.P.P.C.S. (Pre) 1990]

Correct Answer: (a) Silver
Solution:Electrical conductivity is a measure of the amount of electric current which a material can carry. The most electrically conductive element is silver followed by copper, aluminium and iron.

3. Which one of the following is the best conductor of electricity? [U.P.P.C.S. (Mains) 2015]

Correct Answer: (d) Silver
Solution:Electrical conductivity is a measure of the amount of electric current which a material can carry. The most electrically conductive element is silver followed by copper, aluminium and iron.

4. Which of the following is the best conductor of electricity? [U.P.P.C.S. (Mains) 2012 R.A.S/R.T.S.(Pre) 2012]

Correct Answer: (c) Silver
Solution:Electrical conductivity is a measure of the amount of electric current which a material can carry. The most electrically conductive element is silver followed by copper, aluminium and iron.

5. Which of the following liquids is a bad conductor of electricity? [69th B.P.S.C. (PRE) 2023]

Correct Answer: (d) None of the above
Solution:A salt water is completely ionized in water. Hence, it is a good conductor of electricity, Orange and Lemon juice contain various salts and acids and are therefore good conductors of electricity. Thus, option (d) is the correct answer.

6. Assertion (A): Copper rods are generally preferred to iron rods for making lightning conductors. [U.P.R.O/A.R.O. (Mains) 2013]

Reason (R) : Copper is better conductor of electricity than iron and is not easily oxidized under atmospheric conditions.

Code:

 

Correct Answer: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).
Solution:Copper rods are preferred for making lightning conductor because:

(1) Copper is a better conductor of electricity than iron.

(ii) Copper is not easily oxidized in the presence of oxygen and water molecules while iron gets rusted.

(iii) Loss of energy is much less with a copper rod than with iron rod, as copper is a bad conductor of heat than iron.

7. Due to temperature variation along a conductor, potential variation occurs along it. This phenomenon is known as : [67th B.P.S.C. (Pre) (Re. Exam) 2022]

Correct Answer: (a) Thomson effect
Solution:Due to the temperature difference between the two points of the same conductor, there is a difference in the electron density. The electron density is higher at low temperatures than at higher temperatures. Thus, there will be a potential difference between two points of the same conductor .Therefore, when a current (charge) flows in the conductor, work is done against or along the direction of potential difference due to the flow of current. As a result of this heat is absorbed or evolved. This effect is called the Thomson effect.

8. Given below are two statements, in which one is labelled as : [U.P. R.O/A.R.O. (Pre) 2023]

Assertion (A) and the other as Reason (R).

Assertion (A): A person travelling in a car with closed glass windows and doors is safe from the lightening strike.

Reason (R): Actually a closed car behaves like a hollow conductor, so charges cannot enter inside the car. Select the correct answer using the code given below-

Code:

 

Correct Answer: (b) Both (A) and (R) are true and (R) is correct explanation of (A).
Solution:A person travelling in a car with closed glass windows and doors is safe from the lightening strike, because closed car behaves like a closed hollow conductor (as a Faraday cage) and electric field or charge inside a closed conductor is always zero and hence, charges cannot enter inside the car.

9. Which of the following diode is used in ultra-high speed switching electronic circuits? [M.P. P.C.S. (Pre) 2022]

Correct Answer: (c) Tunnel diode
Solution:Tunnel diode is used in ultra-high speed switching electronic circuits. A tunnel diode is a type of semiconductor diode that possesses a high-speed operation capability due to quantum tunneling, making it ideal for ultra-high speed switching circuits. It has effectively 'negative resistance' due to the quantum mechanical effect called tunneling.

10. The characteristic of superconductor is - [39th B.P.S.C. (Pre) 1994]

Correct Answer: (c) Zero permeability.
Solution:In electromagnetism, permeability is a property of a material that describes the ability of a material to support the formation of a magnetic field within itself or we can say that it is the degree of magnetization that a material obtains in response to an applied magnetic field. It is represented by Greek letter μ (Mu). The permeability and electrical resistance of the superconductor is zero.

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