NEET 2020 NEWS
NATIONAL LEVEL OFFLINE TEST
Current Electricity is a field of physics which deals with current, flow of current, resistance of a conductor, electric energy and related concepts. It is one of the main topics of NEET exams and is a very easy topic to score, if prepared thoroughly. To help students prepare for NEET exam, we are providing students with revision notes on Current Electricity which consists of important concepts, formulas, and some tips and tricks to solve current electricity questions.
We have also added some quick notes of current electricity and its sub-topics so that you can quickly cover all the necessary points. Along with this, sample questions of each sub-topics and previous year solved questions are also given in the article.
Electric current is defined as the rate (t) of flow of charges(q) through any cross section in a conductor. It is scalar quantity and its SI unit is Ampere(A).
If the flow of charge is uniform, then,
Electric Current (i) = q/t = ne/t
If the flow of charge is non- uniform, then,
Electric Current (i) = dq/dt or q=? I dt
Different units of electric current are:
Question: The electric current (i) in the circuit given below is?
(c) (1/5) ampere
(d) (1/10) ampere
Ohm’s Law of conductors states that a current flowing through a conductor of uniform area of cross-section at a constant temperature is proportional to the difference of potential across its terminals.
Important equations of Ohm’s Law:
Here V= Voltage, I= current and R= Resistance.
Question: In the given circuit below, current flowing through a 5 ohm resister produces 10 calories of heat per second. Find the heat generated in 4 ohm resister:
Drift Velocity is the velocity through which free electrons are drifted towards positive terminal under the action of the applied field.
V= (eV/ ml)
Here e= Charge of electron, V= potential difference, m= mass and = relaxation time.
Relation between current electricity and drift velocity:
I= q/t= nAve
The ration between potential differences between the two ends of the conductor to the current flowing through it is called as the resistance(R) of a conductor.
Units of Resistance (R)
-1 abohm = 1 abvolt/1 abampere
Variation of Resistance with Temperature
A change in the resistance of the conductor per unit resistance per degree centigrade rise of temperature is defined as Temperature Coefficient of Resistance (α).
Here R0, Rt is the resistance of the conductor at 0º C and tº C respectively.
Question: What will be the resistance of a wire, if a wire is is stretched to make 0.1% longer?
According to Faraday’s Law of Electrolysis,
(a). Mass of an ion deposited on an electrode during the process of electrolysis is proportional to the quantity of charge that has passed through the electrolyte, i.e,
m= Zq= Zlt
(b). When same current passes through several electrolytes at the same time, then, the masses of various ions deposited at each of the electrodes are proportional to their chemical weights, i.e,
or, Z1/Z2= W1/W2
Thus, W/Z= constant= F
Resistance in a series: According to this, if a number of resistances are connected in a series with each other, then the net resistance of the combination is equal to their individual resistances.
Resistance in a Parallel: According to this, if a number of resistances are connected in parallel, then the reciprocal of the resistance of combination is equal to the sum of the reciprocals of their individual resistances, i.e,
Distribution of current in a parallel combination of resistances:
In general, it means, that current in one branch = total current x (resistance of second branch/sum of resistances of both branches).
Question: Given below are 3 resistances of equal value arranged in different combinations. Arrange them in increasing order of power dissipation.
While Current electricity in itself is an important topic to prepare while preparing for JEE Main exam, it also has several important sub-topics which needs to be prepared with due diligence. Some of these topics are mentioned below:
Question: Find the value of constant along the length of the conductor. Considering a steady current is flowing in a metallic conductor which has a non-uniform cross-section.
Question: What will be the minimum capacity of the main fuse of the building if, there are
Question: Find the incorrect statement:
Question: If on interchanging the resistances, balance point of a meter bridge shifts to the left by 10 cm and the resistance of the series is 1k Ω, then find the resistance on the left before interchanging the resistances.
Question: If two bulbs of 25W-220V and 100W-220V are connected in a series of 440V supply then which of these bulbs will fuse?
Question: Find the tolerance of the combination if 400 Ω of resistance is made by adding four 100 Ω resistance of tolerance 5%.
Some tips and tricks to solve the NEET paper are given below:
Since you are time bound, go through all the questions in the beginning and then start by solving the easy questions first, then moderate level questions and if time permits then difficult questions. Thus, you will be able to solve more questions in limited time.
Since the date and time of the examination is available, you can start making your schedule according to the day of exam. Start giving mock tests at the same time at which you have exam on the D-Day. This will help you body and mind ready for the exam day.
On the exam day, read questions twice and then look at the options carefully. Since it is a MCQ paper, elimination method could be applied in some options and thus will save you a lot of time.
In some questions, equations will be given in options. Solving these equations and checking each of them consumes a lots of time. Try solving them by putting numbers, this saves your time and narrows down your options too.
Stay calm and focussed and do not panic if you can’t solve one question. Breathe in, relax and solve next one, and come back to it later on, if you have time.
Since less than 1 month or 30 days is left for NEET 2020, most of you guys would be done with their syllabus, and would be doing revision these days. So here we provide you with a quick revision plan to cover all necessary topics and some do’s and don’ts to help you within this short span of time:
-V = V1+V2+V3
- I = I1 = I2 = I3 = Constant
- V1 = IR1, V2 = IR2, V3 = IR3
-I = I1+I2+I3
- V = V1 = V2 = V3 = Constant
-I1 = V/R1, I2 = V/R2, I3 = V/R3