हिंदी
कर्नाटक बोर्ड पी.यू.सी.पीयूसी विज्ञान कक्षा ११

Consider the Following Statements. (A) Free-electron Density is Different in Different Metals. (B) Free-electron Density in a Metal Depends on Temperature. Seebeck Effect is Caused - Physics

Advertisements
Advertisements

प्रश्न

Consider the following statements.
(A) Free-electron density is different in different metals.
(B) Free-electron density in a metal depends on temperature.
Seebeck Effect is caused _____________ .

विकल्प

  • due to both A and B

  • due to A but not due to B

  • due to B but not due to A

  • neither due to A nor due to B

MCQ
रिक्त स्थान भरें
Advertisements

उत्तर

due to both A and B

 

In Seebeck Effect, a temperature difference between two dissimilar electrical conductors produces a potential difference across the junctions of the two different metals. The cause of this potential difference is the diffusion of free electrons from a high electron-density region to a low electron-density region. The free electron-density of the electrons is different in different metals and changes with change in temperature. Hence, both the statements are the causes of Seebeck Effect.

shaalaa.com
  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
अध्याय 11: Thermal and Chemical Effects of Current - MCQ [पृष्ठ २१८]

APPEARS IN

एचसी वर्मा Concepts of Physics Vol. 2 [English] Class 11 and 12
अध्याय 11 Thermal and Chemical Effects of Current
MCQ | Q 5 | पृष्ठ २१८

संबंधित प्रश्न

What is its relation with relaxation time?


Write its (‘mobility’ of charge carriers) S.I. unit


How does drift velocity of electrons in a metallic conductor vary with increase in temperature? Explain.


On the basis of electron drift, derive an expression for resistivity of a conductor in terms of number density of free electrons and relaxation time. On what factors does resistivity of a conductor depend?


When electrons drift in a metal from lower to higher potential, does it mean that all the free electrons of the metal are moving in the same direction?


Derive an expression for drift velocity of free electrons in a conductor in terms of relaxation time.


When a current is established in a wire, the free electrons drift in the direction opposite to the current. Does the number of free electrons in the wire continuously decrease?


A current of 1.0 A exists in a copper wire of cross-section 1.0 mm2. Assuming one free electron per atom, calculate the drift speed of the free electrons in the wire. The density of copper is 9000 kg m–3.


Consider a wire of length 4 m and cross-sectional area 1 mm2 carrying a  current of 2 A. If each cubic metre of the material contains 1029 free electrons, find the average time taken by an electron to cross the length of the wire.


Consider the following statements.
(A) Free-electron density is different in different metals.
(B) Free-electron density in a metal depends on temperature.

Thomson Effect is caused _______________ .


When a current I is set up in a wire of radius r, the drift velocity is vd· If the same current is set up through a wire of radius 2 r, the drift velocity will be:


Metals are good conductor of heat than insulator because


The identical conductors maintained at same temperature are given potential difference in the ratio 1 : 2. Then the ratio of their drift velocities is ______.


The relaxation time τ is nearly independent of applied E field whereas it changes significantly with temperature T. First fact is (in part) responsible for Ohm’s law whereas the second fact leads to variation of ρ with temperature. Elaborate why?


  1. Consider circuit in figure. How much energy is absorbed by electrons from the initial state of no current (ignore thermal motion) to the state of drift velocity?
  2. Electrons give up energy at the rate of RI2 per second to the thermal energy. What time scale would one associate with energy in problem (a)? n = no of electron/volume = 1029/m3, length of circuit = 10 cm, cross-section = A = (1mm)2


A potential difference (V) is applied across a conductor of length 'L' and cross-sectional area 'A'.

How will the drift velocity of electrons and the current density be affected if another identical conductor of the same material were connected in series with the first conductor? Justify your answers.


The drift velocity of electrons in a conductor connected to a battery is given by vd = `(−"eE" τ)/"m"`. Here, e is the charge of the electron, E is the electric field, τ is the average time between collisions and m is the mass of the electron.

Based on this, answer the following:

  1. How does the drift velocity change with a change in the potential difference across the conductor?
  2. A copper wire of length 'l' is connected to a source. If the copper wire is replaced by another copper wire of the same area of cross-section but of length '4l', how will the drift velocity change? Explain your answer.

Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×