Q9 of 31 Page 18

Temperature dependence of resistivity ρ(T) of semiconductors, insulators and metals is significantly based on the following factors:

The resistivity of a material (ρ) is given by:


Where n is the number of charge carriers per unit volume, m is the mass of the carriers, e is the charge and

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7

Kirchhoff ’s junction rule is a reflection of

 8

Consider a simple circuit shown in Fig 3.2. variable resistance R’. R’ can vary from R0 to infinity. r is internal resistance of the battery (r<<R<<R0).

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 10

The measurement of an unknown resistance R is to be carried out using Wheat stones bridge (see Fig. 3.25 of NCERT Book). Two students perform an experiment in two ways. The first students take R2 = 10Ω and R1 = 5 Ω. The other student takes R2 = 1000 Ω and R1 = 500 Ω. In the standard arm, both take R3 = 5 Ω. Both find within errors.

 11

In a meter bridge the point D is a neutral point (Fig 3.3).


A. The meter bridge can have no other neutral point for this set of resistances.


B. When the jockey contacts a point on meter wire left of D, current flows to B from the wire.


C. When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer.


D. When R is increased, the neutral point shifts to left.