How To Prepare Electricity For National Junior Science Exam

The NSEJS exam has questions from the Class 9 and 10 CBSE syllabus with some miscellaneous topics like thermal properties of matter. For detailed NSEJS syllabus and analysis of NSEJS papers refer to NSEJS Physics paper analysis. Here the discussion is on some tips for how to prepare for NSEJS chapter Electricity from Class 10 NCERT and some important concepts and questions are discussed briefly.

Also Read| IOQJS Paper Analysis

Tips TO Prepare Electricity For NSEJS

• Be through with NCERT Class 10 electricity concepts.

• Go through basic concepts of electrostatics such as Coulomb’s law, properties of electric field and potential.

• Solve NCERT exemplar problems and previous year NSEJS question paper

• Give importance to the concept of combination of resistances and related problems.

• Solve more resistor circuit related problems.

NSEJS Electricity- Important Points To Remember

The concepts given below are not explained in class 10 NCERT in detail. Questions from these concepts are asked in the previous year papers of NSEJS.

Coulomb's Law:

Coulomb's Law states that the force of attraction or repulsion between two charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.

K - proportionality Constant

Q1 and Q2 are two Point charges

In SI unit value of K is

Where

known as absolute permittivity of air or free space

Electric field and electric lines of force

The space around a charge in which another charged particle experiences a force is said to have an electric field in it.

Electric lines of force:

An electric field line is an imaginary line or curve drawn through a region of space so that its tangent at any point is in the direction of the electric field at that point.

Properties of Electric lines of force (Electric field lines):

i) Electric lines of force diverge out from positive charge and converge on the negative charge

ii) The number of field lines is proportional to the magnitude of charge

iii) Lines of force never cross or intersect each other. If they intersect at any point then at that point electric field intensity will have two directions which is not possible.

iv) Electric field lines do not form a closed loop. Since electric field lines cannot start and end on the same charge.

v) The tangent at a point on electric field lines will give the direction of the force on a charged particle placed at that point.

vi) Electric field lines do not give the path of motion of the particle. It may show the path if electric field lines are straight.

vii) Electric field lines are normal to the conductor if it is starting from a conductor or while ending on the conductor.

viii) Uniform electric field is represented by straight, parallel and equidistant lines.

ix) The electric field does not exist inside a conductor.

Galvanometer:

It is an instrument used to detect small current passing through it by showing deflection.

Ammeter: It is a device used to measure current and connected in series

• Conversion of galvanometer into ammeter: Connect a low resistance (shunt) in parallel to the galvanometer

• Required shunt . Where i is the total current, is the galvanometer current

Voltmeter: It is a device used to measure Potential difference and is connected in parallel with circuit element

Conversion of galvanometer into voltmeter: by Connecting a large Resistance R in series.

• .

Wheatstone's Bridge

It is an arrangement of four resistances which can be used to measure one of them in terms of rest

( Balanced condition )

No current will flow through galvanometer

unbalanced condition:

Current will flow from A to B.

Q 1- Each resistance in the adjacent circuit is R Ω . In order to have an integral value for equivalent resistance between A & B, the minimum value of R must be (NSEJS 2018)

c

(a) 4 Ω (b) 8 Ω (c) 16 Ω (d) 29 Ω

Q-2 - Q 17. Choose correct option from the following statements from electrostatics:

(I) If two copper spheres of the same radii, one hollow and the other solid are charged to the same electrical potential, the solid sphere will have more charge.

(II) A charged body can attract another uncharged body.

(III) Electrical lines of force originating from like charges will exert a lateral force on each other, while those originating from opposite charges can intersect each other. (NSEJS 2018)

(a) Only (I) is correct. (b) Only (II) is correct. (c) Only (I) & (II) are correct. (d) All (I), (II) & (III) are correct.

Q-3 - A rectangular metal plate, shown in the adjacent uniformly distributed over it. Then how much is the charge over the shaded area? No part of the metal plate is cut.(NSEJS 2019)

(a) 45 µC (b) 450 µC (c) 15 µC (d) 150 µC

Q-4- . In the adjoining circuit, R = 5 Ω. It is desired that the voltage across Rx should be 6 V, then the value of Rx should be (NSEJS 2020)

(a) 4 Ω (b) 12 Ω (c) 16 Ω (d) 20 Ω

Q-5- In the adjacent circuit, the galvanometer G does not show any deflection. If R= 2 Ω, the current drawn from the cell is(NSEP 2021)

(a) 1 A (b) 9 A (c) 4 A (d) 9/4 A

Refer to the adjacent circuit. The voltmeter reads 117 V and ammeter reads 0.13A. If the resistance of voltmeter and ammeter are 9 kΩ and 0.015Ω respectively, the value of R is___.

(a) 500 Ω (b) 1kΩ (c) 1.5kΩ (d) 2 kΩ

Reference Materials

• NCERT Class 10 Science Book

• NCERT Exemplar Problems From Electricity

• NSEJS Previous Year Question Papers