Would the bulb glow after completing the circuit shown in Fig. 12.14 if instead of safety pin we use an eraser?
The objects through which electricity can pass easily are called conductors and other one from which electricity cannot pass through them are called insulators. For a bulb to glow, there should be presence of conductors. Here bulb is not glowing if we use an eraser at the place of pin because eraser is an insulator of electricity. So, here circuit is not complete, so the bulb will not glow.
Explain why the bulb would not glow in the arrangement shown in Fig. 12.13.
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.
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.
Classify the following fibres as natural or synthetic:
nylon, wool, cotton, silk, polyester, jute
(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.
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?
A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot
iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
What is the composition of air?
Which of the following plants have you seen? of those that you have seen, which one have flowers?
Grass, maize, wheat, chilli, tomato, tulsi, pipal, shisham, banyan, mango, jamun, guava, pomegranate, papaya, banana, lemon, sugarcane, potato, groundnut
Give examples to explain the difference between changes that can or cannot be reversed.
Match the items given in Column A with that in Column B
Column A Column B
Milk, curd, paneer, ghee eat other animals
Spinach, cauliflower, carrot eat plants and plant products
Lions and tigers are vegetables
Herbivores are all animal products
Select those objects from the following which shine:
Glass bowl, plastic toy, steel spoon, cotton shirt