Physics as we know is a vast subject where we can get many information about the day to day practical activities. With the help of physics we can calculate lot of precise value for current, speed, flux, voltage, parabolic range and many more. Here we welcome you to discuss about the most popular Physics topic for Class 12th. We will have a detailed information regarding the Electric Current.
What is Electric Current?
Introduction: Electric current is all about electric charge i.e rate of change of electric charge. Charged particles can be electrons, protons, ions or holes. Movement of these particles effectively produce current in a closed loop. For example a metallic cylindrical wire having length ‘l’, cross-sectional area ‘a’ ,let the ‘n‘ number of charged particles are electron having charge on it is denoted as ‘e’. Place a battery across this metallic wire. Electron will drift with the drift velocity ‘v’. Due to the movement of electrons from one place to another per unit of time current will produce in the opposite direction of flow of electrons.
Current measures in Ampere i.e Amp which is equal to flow of one coulomb per second. According to Ohm’s law current I is flowing through the conductor with voltage V and resistance R, V=IR or I=V/R. You can find solved numerical on Ohm’s Law.
German physicist, Gustav Kirchhoff developed two laws based on conservation of energy and charge which are very helpful to calculate the voltage and current values in the complex circuits like T-network or bridge circuits which are difficult to calculate by using ohm’s law.
Kirchhoff’s current law: KCL is first law of Kirchhoff which is based on the law conservation of charge. It says algebraic sum of entering current and leaving current at node is equal to Zero. This is all dependent on the direction of current flowing in the circuit.
An ideal current source has infinite output impedance.It behave like an open circuit. It is because current follows least resistance path. Ideal current source provide the constant current supply with 100% efficiency. Practical current source does not provide constant current supply therefore efficiency of practical current source can be 98% or 99% but can not be 100%.
The V-I (voltage -current) characteristics can be describe by the following relation for the practical current source and ideal current source.
Basically there is four types of current sources :
- DC Current source
- Time varying non-sinusoidal current source
- Sinusoidal current source
- Controlled and dependent current source.
Properties of Current Source
- Two Resistance connected in series have same current.
- Two resistance connected in parallel have different value of current.
- When a voltage source connected in series with current source then value of voltage source can be ignored.
- If two current source connected in parallel than the total current value is sum or difference of the both current values, depending on their directions(for example:If current source I1 and I2 have same direction then I=I1 + I2 and if I1 and I2 are in opposite direction than I = I1 – I2).
- If two current source have different values connected in series than this not obey KCL and this is invalid situation.
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