Verified answer

1) Case - I : [DC source]

• Current flow = 4A
• Voltage = 12V

As per ohm's law, V = IR

➝ R = V/I

➝ R = 12/4

➝ R = 3Ω ___ (i)

Here R is the resistance of coil

2) Case - II : [AC source]

• Vrms = 12V
• Irms = 2.4A
• ω = 50 rad/s

; ω denotes angular frequency

★ Impedance of circuit (Z) :

➝ Z² = R² + X(L)²

• X(L) denotes inductive reactance

We know that, X(L) = ωL

• L denotes inductance of coil

➝ Z² = R² + ω²L² ___ (ii)

Current flow in AC can be measured by

➝ Irms = Vrms/Z

By squaring both sides, we get

➝ I²rms = V²rms/Z²

➝ Z² = 12²/(2.4)²

➝ Z² = 25

From equation (ii) ...

➝ R² + ω²L² = 0.04

➝ (3)² + (50)²L² = 25

➝ 2500L² = 16

➝ L² = 16/2500

➝ L = 4/50

➝ L = 0.08 H

Capacitor of 2500 μF is now connected in series with the coil.

In order to find power developed in circuit, we need to find impedance of circuit.

★ Impedance of LCR circuit :

➠ Z'² = R² + [X(L)² - X(C)²] ___ (iii)

• X(C) denotes capacitive reactance

A) Inductive reactance :

• X(L) = ωL

• X(L) = 50 × 0.08

• X(L) = 4Ω

B) Capacitive reactance :

• X(C) = 1/ωC

• X(C) = 10⁶/(50×2500)

• X(C) = 8Ω

By substituting the values in (iii),

➠ Z'² = 3² + (4 - 8)²

➠ Z'² = 9 + 16

➠ Z' = √25

➠ Z' = 5Ω

★ Power developed in the circuit :

➠ P = Vrms Irms cos∅

• cos∅ = power factor = R/Z'

➠ P = 12 × 2.4 × 3/5

➠ P = 17.2 watt

Answer:

(a) Adaptations of desert plants and animals:

(i) Adaptations of desert plants:

Plants found in deserts are well adapted to cope with harsh desert conditions such as water scarcity and scorching heat. Plants have an extensive root system to tap underground water. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration. In Opuntia, the leaves are entirely modified into spines and photosynthesis is carried out by green stems. Desert plants have special pathways to synthesize food, called CAM (C4 pathway). It enables the stomata to remain closed during the day to reduce the loss of water through transpiration.

(ii) Adaptations of desert animals:

Animals found in deserts such as desert kangaroo rats, lizards, snakes, etc. are well adapted to their habitat. The kangaroo rat found in the deserts of Arizona never drinks water in its life. It has the ability to concentrate its urine to conserve water. Desert lizards and snakes bask in the sun during early morning and burrow themselves in the sand during afternoons to escape the heat of the day. These adaptations occur in desert animals to prevent the loss of water.

(b) Adaptations of plants to water scarcity

Plants found in deserts are well adapted to cope with water scarcity and scorching heat of the desert. Plants have an extensive root system to tap underground water. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration. In Opuntia, the leaves are modified into spines and the process of photosynthesis is carried out by green stems. Desert plants have special pathways to synthesize food, called CAM (C4 pathway). It enables their stomata to remain closed during the day to reduce water loss by transpiration.

(c) Behavioural adaptations in animals

Certain organisms are affected by temperature variations. These organisms undergo adaptations such as hibernation, aestivation, migration, etc. to escape environmental stress to suit their natural habitat. These adaptations in the behaviour of an organism are called behavioural adaptations. For example, ectothermal animals and certain endotherms exhibit behavioral adaptations. Ectotherms are cold blooded animals such as fish, amphibians, reptiles, etc. Their temperature varies with their surroundings. For example, the desert lizard basks in the sun during early hours when the temperature is quite low. However, as the temperature begins to rise, the lizard burrows itself inside the sand to escape the scorching sun. Similar burrowing strategies are exhibited by other desert animals. Certain endotherms (warm-blooded animals) such as birds and mammals escape cold and hot weather conditions by hibernating during winters and aestivating during summers. They hide themselves in shelters such as caves, burrows, etc. to protect against temperature variations.

(d) Importance of light to plants

Sunlight acts as the ultimate source of energy for plants. Plants are autotrophic organisms, which need light for carrying out the process of photosynthesis. Light also plays an important role in generating photoperiodic responses occurring in plants. Plants respond to changes in intensity of light during various seasons to meet their photoperiodic requirements for flowering. Light also plays an important role in aquatic habitats for vertical distribution of plants in the sea.

(e) Effects of temperature or water scarcity and the adaptations of animals.

Temperature is the most important ecological factor. Average temperature on the Earth varies from one place to another. These variations in temperature affect the distribution of animals on the Earth. Animals that can tolerate a wide range of temperature are called eurythermals. Those which can tolerate a narrow range of temperature are called stenothermal animals. Animals also undergo adaptations to suit their natural habitats. For example, animals found in colder areas have shorter ears and limbs that prevent the loss of heat from their body. Also, animals found in Polar regions have thick layers of fat below their skin and thick coats of fur to prevent the loss of heat.

Explanation:

it is first question answers that you have write