Chapter-3|Current Electricity| NCERT 12th Physics: Limitations of Ohm’s Law: The devices which do not obey Ohm’s law are called non ohmic devices, such a vacuum tube. The relation V/I=R is valid for both ohmic and non ohmic devices. For ohmic conductors value of R is constant. For non ohmic devices, value of R is not […]
Chapter-3|Current Electricity| NCERT 12th Physics: Effect of Temperature on Resistance: Experimentally it was observed that on increasing temperature from T to T+dT, Resistance changes from R₀ to R₀+dR, then For metals the value of α is positive, therefore resistance of the metal increases with rise in temperature. For insulators and semiconductors the value of α is negative, therefore
Chapter-3|Current Electricity| NCERT 12th Physics: Ohm’s Law: It is stated that the current I flowing through a conductor is always directly proportional to the potential difference V across the ends of the conductor, provided that the physical conditions (temperature, mechanical strain, etc) are kept constant. Note: The value of a resistance of a conductor depend
Chapter-3|Current Electricity| NCERT 12th Physics: Electric Current in Conductors: The electrical conductivity of a solid substance depends upon the number of free electron in it. In metals, this number is quite large (nearly 10²⁹/m³). Hence metal are good conductors of electricity. In metals, the electric conduction occurs by the movement of negative charge Carriers (electrons)
Chapter-3|Current Electricity| NCERT 12th Physics: Current Density: The current density at any point inside a conductor is defined as the amount of charge flowing per second through a unit area held normal to the direction of the flow of charge at that point. It is a vector quantity having the same direction as that of
Chapter-3|Current Electricity| NCERT 12th Physics: Electric Current: If two bodies charged to different potentials are connected together by means of conducting wire, charges begin to flow from one body to another. The charges continue to flow till the potential of the two bodies become equal. The flow of electric charges through a conductor constitutes an
Chapter-2|Electrostatic Potential and Capacitance| NCERT 12th Physics: Energy Stored in a Capacitor: The energy of a charged capacitor is measured by the total work done in charging the capacitor to a given potential. The work done in charging the capacitor is stored as its electrical potential energy. Let we consider a capacitor of capacitance C.
Chapter-2|Electrostatic Potential and Capacitance| NCERT 12th Physics: Combination of Capacitors: When there is a combination of capacitors in a circuit, we can sometime replace that combination with an equivalent capacitor. The two basic combinations of capacitors which can be replaced by single equivalent capacitor, are Capacitors in Series: When negative plate of one capacitor is
Chapter-2|Electrostatic Potential and Capacitance| NCERT 12th Physics: Effect of Dielectric on Parallel Plate Capacitor: Let a dielectric is inserted between the plates fully occupying the intervening reason. The dielectric is polarized by the electric field due to two metallic positive and negative plates. Since, the direction of Eᵢ (Induced electric field) and E₀ (External electric
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Chapter-2|Electrostatic Potential and Capacitance| NCERT 12th Physics: Parallel Plate Capacitor: The simplest and the most widely used capacitor is the parallel plate capacitor. It consists of two large plane parallel conducting plates, separated by a small distance. Electric field due to infinite plane sheet X away from positive charge If q is the
