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When we see any object through hot air over the fire, it appears wavy and slightly moving due to the phenomenon of atmospheric refraction. The hot air above the fire has different refractive indices due to temperature variations, causing light passing through it to bend and creating a distorted image.

The resistance of the bulb can be calculated using Ohm's law: R=V/I=330V/110W=3Ω The energy consumed by three bulbs burning for 5 hours is E=P⋅t=110W×3×5h=1650Wh=1.65kWh The cost in rupees is calculated as Cost=Energy consumed×Rate=1.65kWh×0.70 Rupees/kWh=1.155

The resistance of the copper wire can be calculated using the formula R=ρ⋅l/A, where ρρ is the resistivity of copper, ll is the length of the wire, and AA is the cross-sectional area of the wire. Given ρ=1.72×10−8 Ω⋅mρ=1.72×10−8Ω⋅m, l=2 km=2000 ml=2km=2000m, and r=2 mm=0.002 mr=2mm=0.002m (radius),the cross-sectional area A=πr2=π×(0.002)2 m2A=πr2=π×(0.002)2m2. Substituting these values into the formula gives R=(1.72×10−8 Ω⋅m)×(2000 m)π×(0.002)2 m2R=π×(0.002)2m2(1.72×10−8Ω⋅m)×(2000m). Calculating this expression gives the resistance of the wire.

a. When the magnitude of electric current in the wire is increased, the compass needle deflects more, showing a stronger magnetic field around the wire. b. The compass needle is deflected away from the wire because the direction of the magnetic field produced by the current in the wire is opposite to the direction of the magnetic field of the compass needle.

Biogas is considered to be a boon to farmers for several reasons:

1. Energy Production: Biogas provides a renewable source of energy for farmers, which can be used for cooking, heating, and lighting purposes. This reduces their reliance on traditional sources of fuel like wood, dung, or fossil fuels, thereby saving costs and reducing environmental impact.

2. Waste Management: Biogas production involves the anaerobic digestion of organic waste materials such as animal dung, crop residues, and kitchen waste. By converting these waste materials into biogas, farmers can effectively manage and dispose of organic waste while simultaneously producing energy.

3. Fertilizer Production: The byproduct of biogas production, known as digestate, is a nutrient-rich fertilizer. Farmers can use digestate to improve soil fertility and enhance crop yields, reducing the need for chemical fertilizers and promoting sustainable agriculture practices.

• Bad ozone refers to ozone molecules present in the lower atmosphere, also known as ground-level ozone. It is considered "bad" because it is a harmful air pollutant that can cause respiratory problems and damage to vegetation and ecosystems.
• Natural ecosystems are those that occur and develop without human intervention, such as forests, grasslands, and wetlands. Artificial ecosystems, also known as human-made or anthropogenic ecosystems, are deliberately created or modified by humans for specific purposes, such as agricultural fields, urban parks, and gardens.

• Plastic bags are non-biodegradable because they are made from synthetic polymers such as polyethylene, polypropylene, and polyethylene terephthalate (PET), which are resistant to microbial degradation. This means that plastic bags persist in the environment for a long time, contributing to pollution and environmental damage.