Physics XII Content

General
Wave motion
Mechanical waves
Waves in pipes and string
Acoustic phenomena
Nature and propagation of light
Interference
Diffraction
Polarization
D.C. Circuit
Electrical circuits
Thermoelectric effects
Chemical effect of current
Magnetic field
Application of Biot-Savart Law
Application of Ampere’s Law
Helmholtz’s Coil
Magnetic properties of materials
Electromagnetic Induction
Alternating Currents
Electrons and Photons
Solids and semi-conductor devices
Quantization of energy
Nuclear Physics
Radioactivity
Nuclear energy and other sources of energy
Particle physics and cosmology
Universe – Hubble law; Big bang; Critical density; Dark matter
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Current and its direction




Current

The rate of flow of charge in any specific direction is called current. If Q charge flows through a conductor in time t then current is

current

If one coulomb of charge flows through a conductor in one second then the current in the conductor is said to be one ampere.

Direction of Current:

Before the discovery of electron it was considered that current is due to the flow of positive charge. So, the direction of current was assumed to be from positive terminal of battery to the negative terminal of the battery. Later electron was discovered and it was obvious that current is due to the flow of electrons from negative terminal to the positive terminal of the battery. However, till date we assume the direction of current from positive terminal to the negative terminal. This direction of current is called conventional direction of current.

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current flow
Direction of flow of current

Current Carriers

In metals large number of free electrons are available. These free electrons carry negative charges. The flow of these charges contributes current. In case of electrolytes the positive and negative ions are responsible for current through them. In case of semiconductors the combined motion of electrons and hole gives current.

Types of current

DC (Direct Current) : The current whose magnitude and direction remains same throughout the flow of current is called DC.
eg: current due to a battery is DC current.
AC (Alternating Current) : The current whose magnitude and direction changes continuously and periodically is called AC current.
eg: current due to a AC generator is AC current

 



 

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