Electricity — Science STD 10 — Question

If the charge on an electron is 1.6 × 10 coulombs, how many electrons should pass through a conductor in 1 second to constitute 1 ampere current?

With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.

The magnification of an image formed by a lens is –1. If the distance between the object and its image is 60cm, what is the distance of the object from the optical centre of the lens? Find the nature and focal length of the lens. If the object is displaced 20cm towards the optical centre of the lens, where would the image be formed and what would be its nature? Draw a ray diagram to justify your answer.

An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.

A small object is placed 150mm away from a diverging lens of focal length 100mm:

1. Copy the figure below and draw rays to show how an image is formed by the lens.

2. Calculate the distance of the image from the lens by using the lens formula.

Giving reasons, state the ‘signs’ (positive or negative) which can be given to the following:

1. Object distance (u) for a concave mirror or convex mirror.
2. Image distances (v) for a concave mirror.
3. Image distances (v) for a convex mirror.

Why we have two eyes to view the objects?

What will be the resistance of a metal wire of length 2 metres and area of cross-section 1.55 × 10m , if the resistivity of the metal be 2.8 × 10 m?

What would your image look like if you stood dose to a large:

1. Convex mirror?
2. Concave mirror?

Give reasons for your answer.

What is the difference between a good conductor and a poor conductor? Give two example of each.