Current Electricity

Here we will discuss about the importance of "Current Electricity" in JEE advanced , JEE mains and EAMCET and also focus on the types of questions that generally come from this section.

Importance

This topic covers questions only on numerical type when it comes to JEE Mains & Advanced. A brief analysis of previous year papers shows atleast 3 to 5 questions are asked every year in JEE mains, and EAMCET from this topic. These questions are generally formula based and a little practice will help you to score well.

Golden Topics

Numerical type : This part is of atmost importance as it holds questions from Ohm's law, Series and parallel arrangements of resistances and combination of cells, Kirchhoff's laws , Heating effect of current, temperature dependence of resistances, wheatstone bridge, meter bridge, potentiometer applications

This topic must not be neglected as it holds maximum questions .
A brief conceptual and little numerical solving skills will be very helpful for this topic.

Introduction

Current and Resistance

The term electric current, or simply current, is used to describe the rate of flow of charge through some region of space.
Most practical applications of electricity deal with electric currents. For example, the battery in a flashlight supplies current to the filament of the bulb when the switch is turned on.
The SI unit of current is the ampere (A) : !!1A=(1Q)/(1s)!!

Ohm’s law

Ohm’s law states that “ for many materials (including most metals), the ratio of the current density to the electric field is a constant σ that is independent of the electric field producing the current”.

Click here to read more about ohm's law and some problems.

Follow this video for better understanding about ohm's law.

Combination of resistors

Series combination : For a series combination of resistors, the currents in the two resistors are the same because any charge that passes through !!R_1!! must also pass through !!R_2!!. The equivalent resistance of a series connection of resistors is always greater than any individual resistance.

!!R_(eq)= R_1 + R_2!!

Parallel combination : when resistors are connected in parallel, the potential differences across them are the same. The equivalent resistance of two or more resistors connected in parallel is always less than the least resistance in the group.

!!1/(R_(eq))= 1/(R_1) + 1/(R_2)!!

Click here to go through some solved problems.

Follow this video to know more about it.

Kirchhoff’s rules

  1. The sum of the currents entering any junction in a circuit must equal the sum of the currents leaving that junction: !!sumI(i)=sumI(out)!!

2.The sum of the potential differences across all elements around any closed circuit loop must be zero: !!sumV=0!!

Click here to learn more about kirchoffs law and some problems.

Follow this video to get more idea on this.

Some useful videos

  1. RC circuit analysis
  2. Resistivity and temperature
  3. Energy and power in electric circuits