Science case /data -based (4 Marks)

A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic
field. He took a small aluminum rod AB, a strong horse shoe magnet, some connecting wires, a battery and a
switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing
the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of
this phenomenon, answer the following questions :


(a) State the condition under which the displacement of the rod is largest for the same magnitude of current flowing through it.
(b) State the rule that determines the direction of the force on the conductor AB.
(c)
i. If the U shaped magnet is held vertically and the aluminum rod is suspended horizontally with its end
B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced?
ii. Name any two devices that use current carrying conductors and magnetic field.

OR

Draw the pattern of magnetic field lines produced around a current-carrying straight conductor held vertically on horizontal cardboard. Indicate the direction of the field lines as well as the direction of the current flowing through the conductor.

Environmental triggers such as light, or gravity will change the directions that plant parts grow in. These
directional, or tropic, movements can be either towards the stimulus or away from it. So, in two different kinds
of phototropic movement, shoots respond by bending towards light while roots respond by bending away from
it. How does this help the plant? Plants show tropism in response to other stimuli as well. The roots of a plant
always grow downwards while the shoots usually grow upwards and away from the earth. This upward and
downward growth of shoots and roots, respectively, in response to the pull of earth or gravity, is, obviously,
geotropism. If ‘hydro’ means water and ‘chemo’ refers to chemicals, what would ‘hydrotropism’ and ‘chemotropism’ mean? Can we think of examples of these kinds of directional growth movements? One
example of chemotropism is the growth of pollen tubes towards ovules, about which we will learn more when we examine the reproductive processes of living organisms.



(a) Where does negative phototropism occur in plants?
(b) Phototropism in shoots is attributed due to which plant hormone?
(c) Tendrils exhibit/ twining of tendrils show which type of tropic movement?

OR

If the stem grows towards sunlight and the root grows just opposite to it, then what type of movement of the stem is it?

Copper sulphate crystal contains water of crystallisation when the crystal is heated the water is removed and salt
turns white. The crystal can be moistened again with water. The water of crystallisation is the fixed number of
water molecules present in 1 formula unit of copper sulphate. On heating gypsum at 373K, it loses water
molecules and became calcium sulphate hemihydrate.



(a) If the crystal is moistened with water, then which colour of the crystal reappears?
(b) What is the commercial name of calcium sulphate hemihydrate?

OR

Five water molecules are present in one formula unit of copper sulphate.