User:UKPhysics

A best way for SOLVING NUMRICAL problems -- Helpful tips for the students!!!

''Solving any types of numerical is not so easy if we didn't think over the peroblems most seriously, practically and parallelly with the basic concept of theories. The condition used on proving theories are the basic points for solving numericals. However following key points would definitely help you to solve numericals on the basis of examination point of view. Dont forget to read this once!!!!!''

1) Focus on the dimesion: In many cases if you are sincere  about dimensions, you will get some ideas about further steps in some cases:

Illustration: Suppose a car is travelling with a velocity of 5 m/s. How much distance it travells after 10 seconds?

Trick: Here you have asked for the distance to calculate. The dimension of distance is meter (m). How can you get this one? You can see over the given values which is v = 5 m/s and t = 10 s. In these values, to get the dimension of meter (m), you must think to multiply m/s and s so as to get the dimension of meter (m). Now you get the idea of multiplying 5 m/s  and 10 sec to get the required distance.

So, the distance travelled by the car moving with velocity of 5 m/s after 10 second will be 5x10= 50 m Ans.

2) Play with relevant formulas: The second technique is to generate the idea first. How can it be done in the free time? Don't worry. It is very interesting and mind blowing.

I suppose here is that you are well familiar  with the following formulas as;

I) Electric force = qE
 * q is charge [SI Unit Coulomb] and E is electric field intensity or simply electric field.

II) Electric field [By defination, force experienced by an unit positive test charge] = F/q [SI Unit N/C]. In the numerical questions, 2 N/c is the value of E as for instance.

III) Also Electric Field = V/d
 * V is the potential applied between two plates I.e. potential difference between two plates[ SI Unit  volt ] and d is the distance of separation between these two plates [ SI unit m ]. In the numerical questions,  5 V/m is the value of E as for instance.

Note: point I) and II) are mathematically different but  numerically they are equal.

IV) Electrical energy = eV ; e is electronic charge(1.6x10^-19 C) and V is electric potential

V ) Weight = mg Remember all these 5 formulas at first. Write down in your copy.

Now try to exercise over them  more and more....... time and again just by thinking that you are going to be a theoretical scientist so as to derive the new formulas.

Illustration: Srart from any one relation say F=qE. Now you can replace E by the relation E=v/d. Finally,  F= qV/d .... this one is the new formula you have derived, suppose. Can you go further ??? try to think. Yes, E can be replaced by E=F/q.. So F=qF/q=F. you get the same F. Don't laugh so much here.. You are just practicising.

Further, onsider a case of the following figure. - A +q     .......... v = velocity - B In the figure two parallel metal plates A&B are parallel  to each other. The upper plate A is connected with positive terminal of a V volt battery while the lower plate B is connected  with the negative terminal of the same battery. The distance between the plate is d such that there is set up an electric field [E=V/d] with direction from + ve plate towards -ve plate. A charge q is located inside the plate as shown in the fig. Here you can  think over any other condition like,

Case I: q is stationary; What would happens if a charge particle  remains stationary inside the electric field provided between two parallel metal plates A and B?? Imagine the condition. What would happen? What kind of condition there should have? How it becomes stationary at a point? Imagin twice. Because charge particle has mass and hence weight acting downward. To become stationary, what other force would have act? Try to think. Did you get the point? The charge particle is inside the electric field. You must think that charge particle experiences a force i.e. electric force. The electric force must act vertically upward so that it would balances the weight mg. After getting this idea you can freely write the equation ; Electric force=weight. I.e. qE=mg.

Case II: q is not at rest; Here you can imagine this  case in your mind. If the charge particle is not at  stationary, then what should happen? Definately it should be in the motion. If there is motion there is a  particular velocity of the charge particle. Suppose charge particle  gains  straight line motion with linear velocity v. When this condition is true then there is definitely  certain Kinetic energy given by, K.E = 1/2 Mv^2. How this energy was  gained over? It is possibly a  most tricky point and scientific thought. Here you must think that if the charge particle gains the KE, then some external source would have provided it. Try to find out that external source. What is that?Remember, the charge particle is inside the electric field. The electric field is due to the applied potential V between two parallel metal plates. Then you are well familiar with the firmula electrical energy = eV. This energy was given by the electric field  provided by the potential V between the plates A & B and this energy was gained by the electron so as to move with velocity v. Thus, you can generally write the equation of motion in terms of energy as; given energy = taken energy. or, eV=  1/2 mv^2 Give and take just! How much energy is given to the charge particle corresponds to the  amount of energy  taken by the charge particle. Larger is the amount of energy given, greater  is the velocity and hence KE and vice-versa.

In this way you can combine many formulas. That gives you core ideas of general physics. Physics will become most interesting. Any kind of parameter in the equation(I.e the term which can be replaced by its another relation like Electric field in the above case) would be a crossing  bridge for  the last resort. Try to simplify the formula in such a way that all the parameters are given in the question. It is the most important steps for the genious students. Try to be a genious!

3) Roughly note the formulas: If you are in the less practice mode, don't forget to write all the formulas that are given in the chapter at  the top left side of your work sheet. After that just think over the point II).

4) Practice more and more: The more numerical you practice, the more and more condition you will be  known about. Write down the conditions, note the points and revise them all the time. Basically follow the types of numerical you will be asked for the exams. Old is Gold is our proverb. You can follow a  old question bank.

5) Write the units: Never forget to write the Units. Always convert any unit into the corresponding SI units. It will helps you out from the minor mistakes.

6) Remenber by dimension: Remember all the formulas by one time practicing with the concept of dimension.. It will helps you to boost up the missing parameter if that is forgoten.

7) Revise the formula and used conditions: You must revise the formulas and used conditions time and again. You can make a seoarate copy just to point out the short trick in every chapters. It will save your time  and gives you smart concepts forever......