Heredity and Evolution — Science STD 10 — Question

What is the function of an earth wire? Why is it necessary to earth the metallic bodies of electrical appliances?

We often observe domestic waste decomposing in the bylanes of residential colonies. Suggest ways to make people realize that the improper disposal of waste is harmful to the environment.

Why do spores remain viable during unfavorable conditions?

How would a pencil look like if you saw it through (a) a concave lens, and (b) a convex lens? (Assume the pencil is close to the lens). Is the image real or virtual?

A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.

Draw ray-diagrams to show the formation of images when the object is placed in front of a concave mirror (converging mirror):

1. Between its pole and focus.
2. Between its centre of curvature and focus Describe the nature, size and position of the image formed in each case.

Write two examples each of sexually transmitted diseases caused by (i) virus, (ii) bacteria. Explain how the transmission of such diseases be prevented?

Calculate the cost of operating a heater of 500W for 20hours at the rate of? ₹3.90 per unit.

What are the various factors which we should keep in mind while choosing a source of energy?

"We cannot pass on to our progeny the expenences and qualifications earned during our life time". Justify the statement giving reason and examples.