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:


(i) The displacement of the conductor is maximum when the direction of the current is at right angles to the direction of the magnetic field.
ii) The rule that determines the direction of the force on the conductor AB is Fleming's left-hand rule. (
According to Fleming's left-hand rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular.
If the first finger points in the direction of the magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or force.
(iii) i. According to Fleming's left-hand rule, the rod will get displaced upwards.
ii. Devices that use current-carrying conductors and magnetic fields are electric motors, electric generators, loudspeakers, microphones, etc.
OR

Fill a conical flask with water. Cover the neck of the flask with a wire mesh. keep two or three freshly germinated bean seeds on the wire mesh. Take a cardboard box which is open from one side. Keep the flask a wire mesh. Kin the box in such a manner that the open side of the box faces light coming from a window as shown in the given figure. After two or three days, you will notice that the shoots bend towards light and roots away from light. Now turn the flask so that the shoots are away from light and the roots towards the light. Leave it undisturbed in this condition for a few days. 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.

(i) These activities show tropic movements in plants due to their growth.
(ii) Yes, old parts of the shoot and root change direction and there is a difference in the direction of new growth.
(iii)Movement is related to stimulus i.e. plant organs either move towards the source of stimulus or away from it. Stimuli that cause movements in plants are gravity, light, touch, water, and chemical substances.
OR
Movements in the organs of a plant due to gravity are known as geotropism. This causes the roots to bend down towards the soil.

The teacher while conducting practicals in the laboratory divided the students into three groups and gave them various solutions to find out their pH and classify them into acidic, basic and neutral solutions.
Group A - Lemon juice, vinegar, colourless aerated drink
Group B - Tomato juice, coffee, ginger juice
Group C - Sodium hydroxide, sodium chloride, lime water
(i) i. Groups A and Bless than 7
ii. Group C - greater than 7
(ii) pH paper and universal indicator.
OR
i. Copper vessel is tarnished due to formation of basic copper oxide.
ii. Lemon juice being acidic react with copper oxide and the salt formed is washed away.