H = 100 J, R = 4 Ω, t = 1 s, V = ?
From Eq. we have the current through the resistor as
I = √(H/Rt)
= √[100 J/(4 Ω × 1 s)] = 5 A
Thus the potential difference across the resistor, V [from Eq. ] is V = IR = 5 A × 4 Ω = 20 V.

(a) A - Stigma
B - Pollen tube
C - Ovary
D - Female germ cell / Egg cell
(b) Pollination - Transfer of pollen grains from anther to the stigma of a flower.
Significance of pollination - Process of pollination leads to fertilization as it brings the male and female gametes together for fusion.
(c) After a pollen falls on a suitable stigma, the pollen tube grows out of the pollen grain and travels through the style to reach the ovule in the ovary. Here the male germ cell (carried by the pollen tube) fuses with the female germ cell to form a zygote.
(i) Ovule (ii) Ovary

The directional movement of the plant in response to light is called phototropism. The shoots respond by bending towards light and roots respond by bending away from the light.
This happens as follows:
(i) When sunlight falls straight on the plant, the auxin hormone synthesised at the tip of the stem spreads uniformly down the stem and due to equal concentration of auxin, stem grows straight.
(ii) When sunlight falls on only one side of the plant, the auxin diffuses towards the shady side of shoot. The concentration of auxin stimulates the cells to grow longer. Therefore, the stem appears to bend towards the source of light in the directional movement
 

Hydrogen gas is usually liberated when an acid reacts with metal.
e.g. Zn(s) + H₂SO₄ (aq) \(\rightarrow\) ZnSO₄(aq) + H₂ \(\uparrow\)
Test for H₂ gas Testing of H₂ gas presence can be done by passing the gas through soap solution and then bringing a burning splinter near the soap bubble filled with the gas. If the gas burns with a pop sound, it confirms hydrogen.

P.d.(V) between two points=\(\overset { Workdon(W) }{ \underset { charge(Q) }{ \_ \_ \_ \_ \_ \_ } } \)
V = \(\overset { W }{ \underset { Q }{ \_ \_ } } \)
The S.I. unit of electric potential difference is volt (V).
1 volt is the potential difference between two points in a current carrying conductor when 1Joule of work is done in moving a charge of 1 coulomb from one point to another.
\(1 \ volt=\frac{1 \ Joule}{1 \ Coulomb}\)
\(1V=\frac{1J}{1C}\)

Differences between binary fission and multiple fission are given below

In case of a spinal cord injury, signals for reflex actions and involuntary actions will get disrupted.

Differences between movement of leaves and movement of shoot towards light are as follows:

Plant hormones are organic substances produced naturally in higher plants. They control growth and other physiological functions of the plants. These are required in very small amounts.

A layer of basic copper carbonate is formed by the reaction of air on copper metal.
This layer being insoluble in water, cannot be cleaned with water alone. But, it is soluble in acids so lemon containing citric acid, tamarind containing tartaric acid or any other sour substance containing acid can be effective in cleaning the vessels. As these acids neutralises the basic copper carbonate and dissolves the layer. Hence, surface of copper vessels are cleaned with lemon or tamarind juice to give its characteristics lustre.

Unicellular organisms are made up of only a single cell, which performs all the functions necessary for life. So, reproduction is done by simple, asexual methods but in multicellular organisms various cells perform different functions.
So, production of all these specialised cells is required and simple methods for reproduction are insignificant. Thus, they reproduce by sexual reproduction.

Sexual reproduction is considered to be superior over asexual reproduction as it brings about variations in the progeny. These variations allow organisms to live in diverse habitats with the help of adaptations. On the other hand, asexual reproduction does not bring about variations among progeny.