What are relaxation time and mobility?

Important Questions on Current Electricity

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 17

Define relaxation time of the free electrons drifting in a conductor. How is it related to the drift velocity of free electrons? Use this relation to deduce the expression for the electrical resistivity of the material.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 18

Define the terms current density of a metallic conductor. Deduce the relation connecting current density $\left(\mathrm{J}\right)$ and conductivity $\left(\mathrm{\sigma }\right)$ of the conductor when an electric field $\mathrm{E}$ is applied it.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 19

Derive the relation between current density $\mathrm{J}$ and potential difference $\mathrm{V}$ across a current-carrying conductor of length $\mathrm{l},$ area of cross-section $\mathrm{A}$ and the number density $\mathrm{n}$ of free electron density.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 20

 Use Kirchhoff's rule to obtain the balance condition in a Wheatstone bridge.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 20

 Draw a circuit diagram for determining the unknown resistance $R$ using metre bridge. Explain briefly its working, giving the necessary formula used. 

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 21

Write the underlying principle of potentiometer. Draw the current diagram of the experimental set-up used for determining the internal resistance of a cell by potentiometer. Write the necessary formula used.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 22

 State, with the help of a circuit diagram, the working principle of a metre bridge. Obtain the expression used for determining the unknown resistance.

EASY

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 22

 What happens if the galvanometer and cell are interchanged at the balance point of the bridge?