Resistance & Ohm's Law

1 Mark Questions

1.Plot a graph showing variation of current versus voltage for the material GaAs. [Delhi 2014] Ans.

Variation of current versus voltage for the material GaAs.

Negative Non-line (resistance) region region Current (mA) Voltage (V)

1. Show variation of resistivity of copper as a function of temperature in graph. [Delhi 2014; All India 2014]

Ans. Graph of resistivity of copper as a function of temperature is given below (resistivity of metals increases with increase in temperature)

Resistivity <math>\rho(10^{-8} \, \Omega</math>-m) 0.4 0.2

0 50 100 150 Temperature <math>T(K) \longrightarrow</math>

3. Define the term drift velocity of charge carriers in a conductor and write its relationship with the current flowing through it. [Delhi 2014]

Ans. The term drift velocity of charge carriers in a conductor is defined as the average velocity acquired by the free electrons along the length of a metallic conductor under a potential difference applied across the conductor. Its relationship is expressed as <math>v_d = \frac{1}{neA}</math>

where, I is current flowing through the conductor,n is concentration of free electrons e is electron i.e.charge A is cross-sectional area

4.Define the term electrical conductivity of a metallic wire. Write its SI unit. [Delhi 2014] Ans.

The electrical conductivity (<math>\sigma</math>) of a metallic wire is defined as the ratio of the current density to the electric field it creates. Its SI unit is mho per metre.

1. Show variation of resistivity of Si with temperature in graph. [Delhi 2014] Ans.

0 The resistivity of a semiconductor decreases exponentially with temperature.

The variation of resistivity with temperature for semiconductor is shown in figure below.

Resistivity a ₹ semiconductor Temperature T - (1) 6.Define the term mobility of charge carriers in a conductor. Write its SI unit. [Delhi 2014] Ans.