Class 7 Science - Chapter Electric Current and Its Effects NCERT Solutions | Draw in your notebook the symbols to rep

Fig.14.22 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.

Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

In the circuit shown in Fig. 14.25

(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?
(ii) What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Will the compass needle show deflection when the switch in the circuit shown by Fig.14.24 is closed?

When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T/F)
(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)
(c) An electromagnet does not attract a piece of iron. (T/F)
(d) An electric bell has an electromagnet. (T/F)

Zubeda made an electric circuit using a cell holder shown in Fig. 14.4, a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.

Draw the circuit diagram to represent the circuit shown in Fig.14.21.

Fill in the blanks:

(a) Longer line in the symbol for a cell represents its terminal                       .
(b) The combination of two or more cells is called a                     .
(c) When current is switched ‘on’ in a room heater, it                            .
(d) The safety device based on the heating effect of electric current is called a                             .

State similarities and differences between the laboratory thermometer and the clinical thermometer.

State differences between acids and bases.

Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food

Name the elements that determine the weather of a place.

Fill the missing word in the blank spaces in the following statements:

(a) Wind is——————air.
(b) Winds are generated due to —————— heating on the earth.
(c) Near the earth’s surface __________air rises up whereas ___________ air comes down.
(d) Air moves from a region of ——— pressure to a region of ———.

In addition to the rock particles, the soil contains

(i) air and water
(ii) water and plants
(iii) minerals, organic matter, air and water
(iv) water, air and plants

Why does an athlete breathe faster and deeper than usual after finishing the race?

Match structures given in Column I with functions given in Column II.

Column I                           Column II
(i) Stomata                        (a) Absorption of water
(ii) Xylem                           (b) Transpiration
(iii) Root hairs                    (c) Transport of food
(iv) Phloem                        (d) Transport of water
                                          (e) Synthesis of carbohydrates

Fill in the blanks:

(a) Production of new individuals from the vegetative part of parent is called_____________.
(b) A flower may have either male or female reproductive parts. Such a flower is called_____________.
(c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _____________.
(d) The fusion of male and female gametes is termed as _____________.
(e) Seed dispersal takes place by means of _____________, _____________ and _____________.

Classify the following as motion along a straight line, circular or oscillatory motion:

(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry-go-round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bell.
(vi) Motion of a train on a straight bridge.

State the characteristics of the image formed by a plane mirror.

How would you show that setting of curd is a chemical change?

Which of the following relations is correct?

(i) Speed = Distance × Time      (ii) Speed = Distance
                                                                        Time

(iii) Speed = Time                       (iv) Speed =            1          
                   Distance                                      Distance × Time

Which of the two changes frequently, weather or climate?

Match items in Column I with those in Column II:

Column I                             Column II
(a) Bud                                  (i) Maple
(b) Eyes                                (ii) Spirogyra
(c) Fragmentation                 (iii) Yeast
(d) Wings                              (iv) Bread mould
(e) Spores                             (v) Potato
                                              (vi) Rose

Describe the steps involved in getting clarified water from wastewater.

Match the items in Column I with those in Column II:
Column I                             Column II
(a) Yeast                             (i) Earthworm
(b) Diaphragm                    (ii) Gills
(c) Skin                               (iii) Alcohol
(d) Leaves                          (iv) Chest cavity
(e) Fish                               (v) Stomata
(f) Frog                               (vi) Lungs and skin
                                           (vii) Tracheae

Following are some of the characteristics of animals:

(i) Diets heavy on fruits      (ii) White fur
(iii) Need to migrate           (iv) Loud voice
(v) Sticky pads on feet       (vi) Layer of fat under skin
(vii) Wide and large paws  (viii) Bright colours
(ix) Strong tails                   (x) Long and large beak

For each characteristic indicate whether it is adaptation for tropical rainforests or polar regions. Do you think that some of these characteristics can be adapted for both regions?

Fill in the blanks with the appropriate answers:

 (a) People obtain groundwater through________ and ________.                                                                                                                                                         (b) Three forms of water are ________, ________ and ________.
 (c) The water bearing layer of the earth is ________.
 (d) The process of water seepage into the ground is called ________.

You have been asked to maintain a garden. How will you minimise the use of water?