a) What is meant by the term 'frequency' of an alternating current?
b) What is its value in India?
c) An A.C has a frequency of 50 Hz. How many times does it change its direction in one second?
d) Why is an alternating current considered to be advantageous over direct current for long range transmission of electric energy?
a) In a household electric circuit different appliances are connected in parallel to one another. Give two reasons.
b) Why are alloys commonly used in electrical heating devices?
a) Why food chain consists of three or four steps only?
b) Which of the following will have the maximum concentration of harmful?
Chemicals in its body?
Peacock, Frog, Grass, Snake, Grasshopper
c) Why energy of herbivores never come back to the autotrophs?
d) What are decomposers and what is the importance of them in the ecosystem?
a) What is a good source of energy?
b) How charcoal is obtained? Why is charcoal a better fuel when compared to wood?
Question 5: An object of size 5 cm is kept at a distance of 25 cm from the optical center of a converging lens of focal length 10cm. Calculate the distance of the image from the lens and size of the image.
a) How much energy is given to each coulomb of charge passing through a 6 V battery?
b) Calculate the work done in moving a charge of 5 Coulombs from a point at a potential of 210 Volts to another point at 240 Volts.
a)Why does a current carrying conductor kept in a magnetic field experience force? On what factors does the direction of this force depend?
b)Name and state the rule used for determination of direction of this force
When a proton moves in a uniform magnetic field, What happens to these things
5) Kinetic energy
Question 9: Give reason for these
(a) The sky appears to be blue during day time to a person on earth.
(b) The stars appears to twinkle
(c) The planets do not twinkle
a) What is Solar Constant?
b) What are the advantages of Solar Panel