Magnetic Effects of Electric Current — Science STD 10 — Question

Three convex lenses are available having focal lengths of 4cm, 40cm and 4m respectively. Which one would you choose as a magnifying glass and why?

The electronic configuration of an element is 2, 8, 4. State its:

1. Group and period in the modern periodic table.
2. Name and write its one physical property.

Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.

Explain with a suitable diagram, how a concave mirror converges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of concave mirror in this diagram.

What is the commercial unit of electrical energy? Represent it in terms of joules.

Draw diagram to represent the action of a concave mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length ƒ, of the concave mirror.

If work done in moving a charge of 20mC from infinity to a point O in an electric field is 15J, then what is the electric potential at this point?

Draw a schematic diagrams of an electric circuit comprising of 3 cells and an electric bulb, ammeter, plug-key in the ON mode and another with same components but with two bulbs in
parallel and a voltmeter across the combination.

Define the electric resistance of a wire and also write its SI unit.