CBSE Class 12-science Answered

what are the difference between alternating current and direct curent? and what are the use of transformers i.e step up and step down? what is capacitor what is its use ? what is self induction? what is mutual indution? what is a inductor? what is difference between inductor and capacitor?

Asked by baranikerthi5 | 27 May, 2018, 07:37: PM

Expert Answer

Direct current :- current dirction is same in the circuit and never changes

Alternating current :- current direction changes after a specified time. For example domestic electric current ( 230 V , 50 Hz) change its direction for every 20 milli second.

Transformer is used to step up or step down the voltage of alternating electric power. At power station electric power is genertaed at 11 kV. Then it is stepped up to 132 kV at grid sub station and trasmitted to main sub station. In main sub station it is stepped down to 33 kV and electric power is given to heavy industry at 33 kV.Again from main sub station it is transmitted to intermediate sub station. In intermediate substation 33 kV input is stepped down to 11 kV and given to small scale industry. From intermediate substation electric power is transmitted to city sub station. In city sub station 11 kV input is stepped down to 230 V and given to domestic use.

At home-use, some devices may require 6V or 12 V for their operation. In this case, step down transformer is used in the beginning of circuit of device to step down the 230 V alternating voltage to the required voltage.

Capacitor is typically two parallel plates filled with insulating material(dielectric) in between the plates.

These capacitor plates are connected to potential difference and used to collect charges at parallel plates to get steady voltage across plates.

Capacitors are used in electronic circuits and mainly it is used in rectifier circuit which converts AC current to DC current.

Change in current through conducting wire changes magnetic field. change in magnetic field induces current in a conductor. When current is passed through a coil of many number of turns, change in current poroduces a varying magnetic field and this varying magnetic field with respect to time induces current in the coil, which is in opposite direction to the applied current to the coil. This phenomenon is induction and the coil exhibiting this phenomenon is called inductor.

If the above mentioned induction in a coil or inductor is due to the current passing through the same coil, then it is self induction.

If the time varying current in one coil induces current in another coil, then it is mutual inductance.

In capacitor electrical energy is stored as electric field due to electric charges.

In inductor electrical energy is stored as magnetic field due to current.

Answered by Thiyagarajan K | 15 Jun, 2018, 05:42: PM