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Commercial electric motors do not use (a) an electromagnet to rotate the armature (b) effectively large number of turns of conducting wire in the current-carrying coil (c) a permanent magnet to rotate the armature (d) a soft iron core on which the coil is wound

c) a permanent magnet to rotate the armature Explanation In an electric motor, a rectangular coil is placed in between... View Article

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in the figure. In the field an electron and a proton move as shown. The electron and the proton experience (a) forces both pointing into the plane of paper (b) forces both pointing out of the plane of paper (c) forces pointing into the plane of paper and out of the plane of paper, respectively (d) force pointing opposite and along the direction of the uniform magnetic field respectively

(a) forces both pointing into the plane of the paper Explanation For the given figure, the proton and electron are... View Article

For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is (a) The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid (b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil (c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet (d) The N- and S-poles exchange position when the direction of current through the solenoid is reversed

(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field... View Article

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of the paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to (a) A (b) B (c) A if the current is small, and B if the current is large (d) B if the current is small and A if the current is large

(a) A Explanation The direction of the magnetic field will be from south to north pole. Point A is showing... View Article

If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are (a) concentric circles (b) elliptical in shape (c) straight lines parallel to each other (d) concentric circles near the point O but of elliptical shapes as we go away from it

c) Straight lines parallel to each other Explanation If the key in the arrangement is taken out (the circuit is made... View Article

Choose the incorrect statement from the following regarding magnetic lines of the field (a) The direction of the magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points (b) Magnetic field lines are closed curves (c) If magnetic field lines are parallel and equidistant, they represent zero-field strength (d) The relative strength of the magnetic field is shown by the degree of closeness of the field lines

(c) If magnetic field lines are parallel and equidistant, they represent zero-field strength Explanation They have uniform magnetic field and... View Article

Write how the following seeds are dispersed. (a) Seeds with wings. (b) Small and light seeds. (c) Seeds with spines/hooks.

(a) Seeds with wings are dispersed by wind. Due to the winged structure, the wind can easily blow off these... View Article

The male and female gametes fuse to form a _(a) during the process of _(b)__. This grows into an _(c)__ which is enclosed within a seed. After fertilisation the ovules develop into _(d)__ and the ovary develops into a _(e)____ .

The male and female gametes fuse to form an (a) zygote during the process of (b) fertilization. This grows into... View Article

Coconut is a large and heavy fruit. How is it adapted for dispersal by water?

Even though coconut is large and heavy, it contains an outer fibrous coat which has the ability to float on... View Article

When you keep food items like bread and fruits outside for a long time especially during the rainy season, you will observe a cottony growth on them. (a) What is this growth called? (b) How does growth take place?

(a) The growth is called a mould. It is formed by fungus.They are fast-growing fungi and have a cottony appearance... View Article

One morning as Paheli strolled in her garden she noticed many small plants which were not there a week ago. She wondered where they had come from as nobody had planted them there. Explain the reason for the growth of these plants.

Sometimes, plants grow without a human support. New plants are produced from seeds or from vegetative parts. The seeds developed... View Article

Boojho had the following parts of a rose plant – a leaf, roots, a branch, a flower, a bud and pollen grains. Which of them can be used to grow a new rose plant?

Branch, pollen grains. Rose flower is a bisexual flower. Rose plant can be grown by vegetative propagation as well as... View Article

Pick the odd one out from the following on the basis of mode of reproduction and give reason for it. (sugarcane, potato, rice, rose)

Rice Explanation Vegetative propagation is an asexual method of plant reproduction that occurs in its leaves, roots and stem. This... View Article

Fungus, moss and fern reproduce by a common method of asexual reproduction. Name the method.

Spore formation Explanation The method of asexual reproduction found in fungus, moss and fern is spore formation. The parent plant... View Article

Pollination refers to the (a) transfer of pollen from the anther to the ovary. (b) transfer of male gametes from the anther to stigma. (c) transfer of pollen from the anther to stigma. (d) transfer of pollen from the anther to the ovule.

(c) transfer of pollen from anther to stigma. Explanation Pollination is a method where pollen grains are picked from an... View Article

Which of the following statements is/are true for sexual reproduction in plants? (i) Plants are obtained from seeds. (ii) Two plants are always essential. (iii) Fertilisation can occur only after pollination. (iv) Only insects are agents of pollination. Choose from the options given below. (a) (i) and (iii) (b) (i) only (c) (ii) and (iii) (d) (i) and (iv)

a) (i) and (iii) Explanation In sexual reproduction, new plants are produced from seeds.Two plants are not always necessary for... View Article

The ovaries of different flowers may contain (a) only one ovule (b) many ovules (c) one to many ovules (d) only two ovules

(c) one to many ovules Explanation It is the ductless reproductive gland that holds a lot of ovules. It is... View Article

The ‘eye’ of the potato plant is what (a) the root is to any plant. (b) the bud is to a flower. (c) the bud is to Bryophyllum leaf. (d) the anther is to stamen

c) The bud is to Bryophyllum leaf. Explanation The leaves of a Bryophyllum plant have special buds in their margins... View Article

Seeds of drumstick and maple are carried to long distances by wind because they possess (a) winged seeds (b) large and hairy seeds (c) long and ridged fruits (d) spiny seeds

a) Winged seeds Explanation Seeds of maple and drumstick have wings. The winged seeds help them to travel long distances... View Article

Lila observed that a pond with clear water was covered up with green algae within a week. By which method of reproduction did the algae spread so rapidly? (a) Budding (b) Sexual reproduction (c) Fragmentation (d) Pollination

c) Fragmentation Explanation An alga breaks up into two or more fragments. These fragments or pieces grow into new individuals.... View Article

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