Explain why the bulb would not glow in the arrangement shown in Fig. 12.13.
The bulb would not glow in this arrangement because, the terminals of the bulb are connected to the insulator part (plastic) to the screw driver. Here the circuit is not complete. For the bulb to glow, there must be a conductor that will be connected to the electric cell.
Would the bulb glow in the circuit shown in Fig. 12.15?
Using the "conduction tester" on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.
Would the bulb glow after completing the circuit shown in Fig. 12.14 if instead of safety pin we use an eraser?
Mark 'True' or 'False' for following statements:
(a) Electric current can flow through metals.
(b) Instead of metal wires, a jute string can be used to make a circuit.
(c) Electric current can pass through a sheet of thermo Col.
Complete the drawing shown in Fig 12.14 to indicate where the free ends of the two wires should be joined to make the bulb glow.
Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.
Fill in the blanks :
(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
(a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Do you find that all living beings need the same kind of food?
Name the major nutrients in our food.
Classify the following fibres as natural or synthetic:
nylon, wool, cotton, silk, polyester, jute
Name five objects which can be made from wood.
Why do we need to separate different components of a mixture? Give two examples.
Correct the following statements and rewrite them in your notebook.
(a) Stem absorbs water and minerals from the soil.
(b) Leaves hold the plant upright.
(c) Roots conduct water to the leaves.
(d) The number of petals and sepals in a flower is always equal.
(e) If the sepals of a flower are joined together, its petals are also joined together.
(f) If the petals of a flower are joined together, then the pistil is joined to the petal.
Fill in the blanks:
(a) Joints of the bones help in the ——————— of the body.
(b) A combination of bones and cartilages forms the _______ of the body.
(c) The bones at the elbow are joined by a ______________________ joint.
(d) The contraction of the _____________ pulls the bones during movement.
Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?
Give an example of a non-living thing, which shows any two characteristics of living things.
If a plant has fibrous root, what type of venation do its leaves likely to have?
Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.
S.No. | Change | Can be reversed (Yes/ No) |
---|---|---|
1 | The sawing of a piece of wood | |
2 | The melting of ice candy | |
3 | Dissolving sugar in water | |
4 | The cooking of food | |
5 | The ripening of a mango | |
6 | Souring of milk |
Where are poles of a bar magnet located?
Given below are the names of some objects and materials:
Water, basket ball, orange, sugar, globe, apple and earthen pitcher Group them as:
(a) Round shaped and other shapes
(b) Eatables and non eatables
Do you think it is better to use compost instead of chemical fertilisers? Why?
Why do we need to separate different components of a mixture? Give two examples.
State whether the statements given below are True or False.
(i) Stone is transparent, while glass is opaque.
(ii) A notebook has lustre while eraser does not.
(iii) Chalk dissolves in water.
(iv) A piece of wood floats on water. (v) Sugar does not dissolve in water.
(vi) Oil mixes with water.
(vii) Sand settles down in water.
(viii) Vinegar dissolves in water.
(a)Collect different kinds of packaging material. What was the purpose for which each one was used? Discuss in groups.
(b) Give an example in which packaging could have been reduced?
(c) Write a story on how packaging increases the amount of garbage.