Stable emulsions can be produced by using emulsifying agents. These agents reduce the interfacial tension between the two phases and then separate the globules by creating a barrier at the interface. Surfactants are mainly used as emulsifying agents. The emulsifying agent’s solubility determines the kind of emulsion to be prepared. If using hydrophilic emulsifying agents
Emulsion Formulation by HLB Method Read More »
S.No. n-type semiconductor p-type semiconductor 1. N-type semiconductor is obtained by doping an intrinsic semiconductor with pentavalent impurity. P-type semiconductor is obtained by doing an intrinsic semiconductor with a trivalent impurity. 2. Here electrons are majority carriers and holes are minority carriers. Here holes are majority carriers and electrons are minority carriers. 3. It has
Difference Between N & P Type Semiconductor Read More »
A semiconductor to which a suitable impurity in a controlled rate is added to increase its conductivity is called an extrinsic semiconductor. Based on the type of impurity added they are classified into two types. They are, n-type semiconductor p-type semiconductor N-type semiconductors Definition: When a small amount of pentavalent impurity or element with five
Extrinsic Semiconductors (P-type and N-type) Read More »
Based on the composition of elements they are classified into two types. They are S.No. Elemental semiconductors Compound semiconductors 1. These are made from single element These are made from compound (mixed elements) 2. These are made from IV group elements of periodic table These are made from III and V [or] II and VI
Elemental and Compound Semiconductors Read More »
Emulsification is the method of dispersing a liquid in another immiscible liquid, The major groups of emulsifying agents are soaps, detergents, and compounds whose basic structure is a paraffin chain ending in a polar group. Bancroft stated that the essential conditions for a stable emulsion are that the drops of the dispersed phase should be
Theories of Emulsification – Pedagogy Zone Read More »
A biphasic liquid preparation containing two immiscible liquids, one of which is dispersed as minute globules into the other, is termed as pharmaceutical emulsion. The liquid in the form of minute globules is the dispersed phase, while the liquid containing the dispersed globules is the continuous phase. An emulsifying agent is added to disperse two
Emulsions : Introduction, Classification – Pedagogy Zone Read More »
Flocculated and deflocculated suspension: The formulation of a suspension possessing optimal physical stability depends on whether the particles in suspension are to be flocculated or to remain deflocculated. First approach involves use of a structured vehicle to keep deflocculated particles in suspension; a second depends on controlled flocculation as a means of preventing cake formation.
Formulations of Flocculated and Deflocculated Suspensions Read More »
Classical free electron theory could not explain many physical properties. This drawbacks of classical theory can be rectified using quantum theory. The failures of classical theories were removed by Sommerfield in 1928. He developed a new theory applying quantum mechanical concepts and Fermi-Dirac statistics to the free electrons in the metal. This theory is called
Quantum Theory – Pedagogy Zone Read More »
The classical free electron theory has been successfully applied to explain the various properties of metal. It is used to verify Ohm’s law It is used to derive Wiedemann-Franz law. It explains the electrical and thermal conductivities of metals. It explains optical properties of metals. It correctly predicts different resistivities of various metals. Limitations of
Success of Classical Free Electron Theory Read More »
The electrical conductivity is defined as the rate of electric charges flows across a unit area in a unit time per in a conductor per unit potential gradient (or) electric field. It is denoted by σ. [latex] \begin{aligned} \sigma & =\frac{\mathrm{Q}}{\mathrm{AtE}} \quad\left(\text { Since } \mathrm{J}=\frac{\mathrm{I}}{\mathrm{A}}: \mathrm{I}=\frac{\mathrm{Q}}{\mathrm{t}}: \mathrm{J}=\frac{\mathrm{Q}}{\mathrm{At}}\right) \\ \sigma & =\frac{\mathrm{J}}{\mathrm{E}} \mathrm{ohm}^{-1} \mathrm{~m}^{-1} \end{aligned}
Electrical Conductivity (σ) – Pedagogy Zone Read More »