Sources of Energy — Science STD 10 — Question

What shape are your eye-lenses:

1. When you look at your hand?
2. When you look at a distant tree?

Where would the image be formed by a convex mirror if the object is placed:

1. Between infinity and pole of the mirror?
2. At infinity?

Draw labelled ray-diagrams to show the formation of image in both the cases.

In an experiment to study the relation between the potential difference across a resistor and the current through it, a student recorded the following observations:
  

Potential V (volts)	1.0	2.2	3.0	4.0	6.4
Current I (ampere)	0.1	0.2	0.6	0.4	0.6

On examining the above observations the teacher asked the student to reject one set of readings as the values were out of agreement with the rest. Which one of the above sets of readings can be rejected? Calculate the mean value of resistance of the resistor based on the remaining four sets of readings.

An extended object in the form of an arrow pointing upward has been placed in front of plane mirror. Draw a labelled ray-diagram to show the formation of its image.

Explain why, concave mirrors are used as shaving mirrors.

Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?

Name four appliances wherein an electric motor, a rotating device that converts electrical energy to mechanical energy, is used as an important component. In what respect motors are different from generators?

A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil appear to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine. Support your answer with reason.