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## Equilibrium – Numerical Problem

SOLID HEMISPHERE OF RADII R EACH, are placed in contact with each other with each other with their flat faces on a rough horizontal surface. A sphere of mass m and radius R is placed symmetrically on top of them. The normal reaction between the top sphere and any hemisphere assuming the system to be in state equilibrium is ## A Numerical problem from electricity

In the given diagram,the cell and the ammeter, both have negligible resistance. the resisitors are identical. With switch K open , the ammeter reads 0.6 A. What will be the ammeter reading when the switch is closed?

When the switch is open, the effective resistance is R/2, since the two resistances R each are in parallel.

Therefore, the pd, V = I x R/2 = 0.6 x R/2 = 0.3 R

When the key is closed, the effective resistance becomes R/3

Now the reading of the ammeter, I’ = V/(R/3) = 0.3R/(R/3)=0.9A Sample QP & Marking Schemes for Board Exam 2009     Practical Skills in Science & Technology Class X          ## Human Eye and the Colorful World – An online test

Class X students can practice this online Fill in the Blanks test and get evaluated online instantly. The sentences are taken from NCERT Text Book. This is an excellent way of revising fast.

Click the link below to start

Fill in the Blanks Exercise from Human Eye and the Colorful World

## Is vacuum a Dielectric?

Is vacuum a Dielectric. If so how? please explain physically and mathematically

Vacuum cannot be considered as a dieletric.

A dielectric is defined as an insulating material which can be polarized by applying electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, but only slightly shift from their average equilibrium positions causing dielectric polarization.

Nothing like that will happen in the case of vacuum.

But in theory, if necessary, vacuum can be considered as a dielectric medium of dielectric constant unity.

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