Electric Field

Question 1(Grade 12 SA:Year2010)

Two point charges Q1 and Q2 a distance 4m apart are shown below .The charge on Q1 is -14μC and the charge on Q2 is +20μC.

1.1)            Define the electric field at a point in space.

1.2)            Draw the electric field pattern due to these two charges.

1.3)            Calculate the net electric field at point P situated 2m from Q2.                                                                                                                                                                                                           

Question 2

Two charged metallic plates are placed 15cm apart in vacuum and are kept at a p.d of 450V. An electron is released from rest at a point close to the negative plate .How long it will take to reach the other plate and with what velocity?(Mass of electron = 9.1x 10^-31Kg and charge of electron = 1.6x 10^-19C).

Answer

a. Electric dipole

b. τ = P× E

= PESinθ     ,(θ = 90:Sin90=1 )

= QaE

= 3×10^-6 ×5×10^-3×3×10^-5

= 45×10^-14 Nm

c. both translational motion and rotational motion

Electro statics

Two charges +3μ C and -3 μ C are separated by a very small distance of 5 m.m.
a). What is the name of the above arrangement
b). If the above arrangement is placed in a uniform electric field of intensity 3×10-5 N/C with
its axis perpendicular to the field direction, what is the torque acting on it?
c. If the arrangement is placed in a non uniform electric field, what happens?

Electro statics- (Answers)

Electro statics- (Questions)

1) By how many times the force between two charged bodies gets increased ,if their charges are doubled and the distance between them is halved?


2) Two pith-balls of mass 0.0004Kg are suspended from the same point by silk threads 0.25m long.Equal charges are given to the balls which separate until the threads enclose an angle of 30 degree. Calculate the charge on each pith-ball.


3) Two point charges whose magnitudes are in the ratio 2:3 separated by 2cm repel each other with a force of 3375N .Find the magnitude of the charges.


4)Two charged identical lead balls P and Q have their centres separated by a distance of 3cm and carries a charge of 9μC each.A third identical lead ball R is brought in contact with P and removed.It is then  brought in contact with Q and removed.What is the new force of repulsion between P and Q?

Inclined Plane Problem Answer

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Inclined Plane Problem

A rope rests on two platforms which are both inclined at an angle θ. The rope has uniform mass density, and its coefficient of friction with the platforms is 1. The system has left-right symmetry. What is the largest possible fraction of the rope that does not touch the platforms? What angle θ allows this maximum value?

                             

Teaching and Learning Physics:A Joint Interaction between Educator,Scientist,Social Net Work and Learners

This topic describes a new form of co-ordination between learners and other community members.For the better development of Physics thoughts and dreams,we want to start a new course in Schools and Universities.This closed system will manage Physics teaching and learning and also it will help the community to think scientifically.In this model for a physics course, the students engage in activities that engender both broad-based skills which span these domains (e.g. problem solving, analysis, and meta-cognition) as well as specialized domain-specific knowledge and skills (e.g. physics content, and knowledge of and practice in theories of teaching).  In addition, the course is designed to be flexible enough to capitalize on the emergent nature of the activity.  That is, because the participants, locales, and even the content are dynamic in nature, the precise form of the activity changes over time. The assertion is not that physics itself is changing (though many may argue about the social construction of the discipline), but rather since the course structure is flexible, it allows the coordinated activities to adapt to local context.