Fill ups
The ……………., a property of materials C, Si and Ge, depends upon the energy gap between their conduction and valence bonds.

Energy of the photon of sodium light of wavelength 5,890 overset @A equals the energy gap between valence and conduction band of a semiconductor. Find the minimum energy E required to create a hole-electron pair.

The question given below consist of an assertion (A) and a reason ( R). Use the following key to choose the appropriate answer to these questions from the codes (a), (b), ( c) and (d) given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is NOT the correct explanation of A. (c) A is true but R is false. (d) A is false and R is also false. Assertion:The resistivity of a material depends upon the shape and size of the conductor. Reason:The resistance of a conductor is directly proportional to its length.

The question given below consist of an assertion (A) and a reason ( R). Use the following key to choose the appropriate answer to these questions from the codes (a), (b), ( c) and (d) given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is NOT the correct explanation of A. (c) A is true but R is false. (d) A is false and R is also false. Assertion: The energy gap between the valence band and conduction band is greater in silicon than germanium. Reason: Thermal energy produces fewer minority carries in silicon than in germanium.

Fill ups If there is a large energy gap between the filled valence band and empty conduction band, the subtance acts as …………….. .

A parallel plate capacitor consists of two thin conducting plates each of area A held parallel to each other at a suitable distance d. insulating medium is generally filled between the plates. On introducing a non-conducting or insulating slab between the plates, the capacitance of the capacitor? a) decreases b) increases c) becomes zero d) nothing

In an intrinsic semiconductor the energy gap E_g is 1.2eV . Its hole mobility is much smaller than electron mobility and independent of temperature. What is the ratio between conductivity at 600K and that at 300K? Assume that the temperature dependence of intrinsic carrier concentration ni is given by n_i= n_0 exp((E_g)/(2k_BT)) where n_0 is constant.

According to collision theory of chemical reactions, rate of a reaction depends upon collision frequency and fraction of effective collisions. The rate of a reaction generally increases with rise in temperature mainly because of increase in number of effective collisions. Arrhenius proposed a quantitative relation between rate constant and temperature as k= Ae^(-E_a//Rt) where E_a is activation energy. It is equal to the difference between threshold energy and average kinetic energy of reacting molecules. Which of the following plot will be linear ?

A parallel plate capacitor consists of two thin conducting plates each of area A held parallel to each other at a suitable distance d. insulating medium is generally filled between the plates. If a dielectric constant k is introduced between the plates of the capacitor, the capacitance of the capacitor becomes a) kε/A b) kε/d c) kεA/d d)∞

The question given below consist of an assertion (A) and a reason ( R). Use the following key to choose the appropriate answer to these questions from the codes (a), (b), ( c) and (d) given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is NOT the correct explanation of A. (c) A is true but R is false. (d) A is false and R is also false. Assertion: Kinetic energy of photo electrons emitted by a photosensitive surface depends upon the intensity of incident photon. Reason: The ejection of electrons from metallic surface is possible with frequency of incident photon below the threshold frequency.