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प्रश्न
Why alloys like constantan and manganin are used for making standard resistors?
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उत्तर
Alloys like constantan and manganin are used for making standard resistors because
(a) they have high value of resistivity
(b) temperature cofficient of resistance is less
संबंधित प्रश्न
Derive an expression for drift velocity of free electrons.
What is its relation with relaxation time?
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?
Metals are good conductor of heat than insulator because
The drift velocity of a free electron inside a conductor is ______
- 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?
- 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
The potential difference applied across a given conductor is doubled. How will this affect (i) the mobility of electrons and (ii) the current density in the conductor? Justify your answers.
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.
Which expression gives the drift velocity in terms of electric field \[E\], relaxation time \[\tau\], electronic charge \[e\], and electron mass \[m\]?
Why can current be established almost instantly even when drift speed is only a few millimetres per second?
