Electric Current and Its Effects

Electricity plays a very important role in our daily life. From lighting our homes to running fans, televisions, and mobile chargers, electricity is everywhere. In this chapter, we will learn about electric current and the different effects of electric current.

What is Electric Current?

Electric current is the flow of electric charges through a conductor. In simple words, when electricity flows through a wire, it is called electric current.

Electric current flows only when:

• There is a source of electricity (cell or battery)
• The circuit is complete (closed circuit)

Electric Circuit

An electric circuit is a complete path through which electric current flows. It usually consists of:

• Electric cell or battery
• Connecting wires
• Switch (key)
• Electric device (bulb, buzzer, etc.)

If the switch is ON, the circuit is complete and current flows. If the switch is OFF, the circuit is broken and current does not flow.

Effects of Electric Current

When electric current flows through a conductor, it produces different effects. The two main effects discussed in this chapter are:

• Heating Effect of Electric Current
• Magnetic Effect of Electric Current

Heating Effect of Electric Current

When electric current passes through a wire, the wire becomes hot. This is called the heating effect of electric current.

Examples of heating effect:

• Electric iron
• Electric heater
• Toaster
• Electric bulb (filament glows due to heat)

The filament of an electric bulb is made of tungsten because it can withstand very high temperatures without melting.

Magnetic Effect of Electric Current

When electric current flows through a wire, it produces a magnetic field around it. This is known as the magnetic effect of electric current.

This effect is used to make electromagnets.

Electromagnet

An electromagnet is a temporary magnet formed when electric current passes through a coil of wire wound around an iron core.

Uses of electromagnets:

• Electric bell
• Electric motors
• Magnetic cranes
• Relays and switches

Electric Bell

An electric bell works on the principle of the magnetic effect of electric current. When the switch is pressed, current flows through the coil, turning it into an electromagnet. This attracts the iron armature and produces a ringing sound.

Safety Measures While Using Electricity

• Never touch electric switches with wet hands
• Do not insert metal objects into sockets
• Use proper insulation for wires
• Switch off power before repairing appliances

Conclusion

Electric current is a powerful and useful form of energy. Its heating and magnetic effects are used in many devices that make our life easier. However, electricity must be used carefully to avoid accidents.

© Class 7 Science | Electric Current and Its Effects

Respiration in Organisms

Respiration in Organisms – Class 7 Science

Respiration is one of the most important life processes. All living organisms need energy to grow, move, repair tissues, and perform daily activities. This energy is released from food through the process of respiration.

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What is Respiration?

Respiration is the process by which living organisms break down food in the presence or absence of oxygen to release energy. The energy released is used for various life activities.

Equation of Respiration:

Glucose + Oxygen → Carbon Dioxide + Water + Energy

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Difference Between Breathing and Respiration

Breathing	Respiration
Physical process	Chemical process
Involves inhaling and exhaling air	Involves breakdown of food
Occurs in respiratory organs	Occurs inside cells

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Types of Respiration

1. Aerobic Respiration

Aerobic respiration takes place in the presence of oxygen. It releases a large amount of energy.

• Occurs in most plants and animals
• Produces carbon dioxide and water
• More efficient process

2. Anaerobic Respiration

Anaerobic respiration occurs in the absence of oxygen. It releases less energy.

• Occurs in yeast and some bacteria
• Produces alcohol or lactic acid
• Less efficient

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Respiration in Humans

Humans breathe through lungs. The air enters through the nose, passes into the lungs, and oxygen is absorbed into the blood. Carbon dioxide is released during exhalation.

Steps involved:

1. Inhalation of oxygen
2. Transport of oxygen by blood
3. Release of energy in cells
4. Exhalation of carbon dioxide

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Respiration in Other Animals

• Fish: Gills
• Insects: Spiracles
• Earthworms: Skin
• Frogs: Skin and lungs

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Respiration in Plants

Plants respire through small openings called stomata. Oxygen enters the plant and carbon dioxide is released. Respiration occurs all the time, even at night.

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Importance of Respiration

• Provides energy for life processes
• Helps in growth and repair
• Maintains body temperature
• Essential for survival

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Key Points to Remember

• Respiration is essential for life
• Breathing and respiration are different
• Energy is released during respiration
• All living organisms respire

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📘 Class 7 Science – Respiration in Organisms
Easy Notes | Exam Oriented | Student Friendly

Human Body and Its Parts

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The human body is a wonderful and complex structure made up of many parts that work together to help us live, grow, and stay healthy. Each part of the body has a special function.

Main Parts of the Human Body

The human body can be divided into the following main parts:

• Head
• Neck
• Trunk
• Arms
• Legs

Internal Body Parts

Internal organs are inside our body and help in vital functions:

• Brain: Controls thinking, memory, and body movements.
• Heart: Pumps blood to all parts of the body.
• Lungs: Help us breathe oxygen.
• Stomach: Helps in digestion of food.
• Kidneys: Remove waste from blood.

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Sense Organs

Sense organs help us understand the world around us:

• Eyes: Help us see
• Ears: Help us hear
• Nose: Helps us smell and breathe
• Tongue: Helps us taste
• Skin: Helps us feel touch

Importance of the Human Body

Taking care of our body is very important. Eating healthy food, exercising daily, and maintaining cleanliness help us keep our body fit and strong.

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Conclusion

The human body is like a machine where every part has an important role. Proper care and healthy habits help our body work efficiently.

© 2026 | Educational Content | Human Body & Science

Water: A Precious Resource

Class: 7 | Subject: Science

Introduction

Water is one of the most important natural resources on Earth. All living organisms — plants, animals, and humans — need water to survive. Although about 71% of the Earth’s surface is covered with water, only a small portion of it is fresh and usable for human needs. Therefore, water is called a precious resource and must be used wisely.

Sources of Water

Water comes from different natural sources. These include:

• Rain
• Rivers
• Lakes and ponds
• Groundwater (wells, tube wells, hand pumps)
• Glaciers and snow

Rain is the main source of fresh water. It fills rivers, lakes, and also seeps into the ground to form groundwater.

The Water Cycle

The water cycle is the continuous movement of water between the Earth and the atmosphere. It consists of four main stages:

• Evaporation: Water from oceans, rivers, and lakes changes into water vapor due to heat from the sun.
• Condensation: Water vapor cools down and forms clouds.
• Precipitation: Water falls back to the Earth as rain, snow, or hail.
• Collection: Water collects in rivers, lakes, oceans, and underground.

Groundwater

Groundwater is the water found below the surface of the Earth in the spaces between soil particles and rocks. It is an important source of water for drinking and irrigation. Excessive use of groundwater can lead to a fall in the water table, which may cause wells and hand pumps to dry up.

Depletion of Water Resources

Water resources are depleting due to:

• Overuse of groundwater
• Increasing population
• Deforestation
• Industrial pollution
• Wastage of water

Water Conservation

Conserving water means using it carefully and preventing wastage. Some simple methods to conserve water are:

• Fix leaking taps and pipes
• Use buckets instead of showers
• Reuse water for gardening or cleaning
• Practice rainwater harvesting
• Grow trees to increase groundwater recharge

Rainwater Harvesting

Rainwater harvesting is the process of collecting and storing rainwater for future use. It helps in reducing water shortage and increases the groundwater level. This method is eco-friendly and cost-effective.

Conclusion

Water is essential for life and must be protected. By understanding the importance of water and practicing conservation methods, we can ensure that enough water is available for future generations. Every small effort to save water makes a big difference.

© 2026 | Educational Content | Prepared for learning purposes

Compounds and Their Properties

A compound is a pure substance formed when two or more elements combine chemically in a fixed ratio. The elements lose their individual properties and the compound formed has new properties.

Characteristics of Compounds

• Compounds are formed by chemical combination of elements.
• The composition of a compound is always fixed.
• Properties of a compound are different from its elements.
• Compounds cannot be separated by physical methods.

Properties of Compounds

Some important properties of compounds are:

• They have a fixed chemical formula.
• They have a definite melting and boiling point.
• They are usually homogeneous in nature.
• They undergo chemical reactions to form new substances.

Examples of Compounds

1. Water (H₂O)
Formed by chemical combination of hydrogen and oxygen in the ratio 2:1. Water is a liquid used for drinking, washing, and many daily activities.

2. Carbon Dioxide (CO₂)
Formed from carbon and oxygen. It is a gas used by plants for photosynthesis.

3. Sodium Chloride (NaCl)
Formed from sodium and chlorine. It is commonly known as common salt and is used in food.

Difference Between Elements and Compounds

Elements	Compounds
Consist of only one type of atom.	Consist of two or more elements chemically combined.
Cannot be broken down chemically.	Can be broken down by chemical methods.
Example: Oxygen, Iron	Example: Water, Salt

Conclusion

Compounds are important substances that form the basis of materials used in daily life. Understanding compounds helps us know how different substances are formed and used around us.

Weather, Climate and Adaptations of Animals to Climate

Class: 7   |   Subject: Science

This chapter explains the difference between weather and climate and how animals adapt themselves to survive in different climatic conditions.

1. What is Weather?

Weather is the condition of the atmosphere at a particular place and time. It can change from hour to hour or day to day.

• Sunny
• Rainy
• Windy
• Cold or hot

Weather includes temperature, humidity, rainfall, wind speed and cloud cover.

2. What is Climate?

Climate is the average weather pattern of a place over a long period (about 25 years or more).

Example: Rajasthan has a hot and dry climate, while Kerala has a hot and wet climate.

3. Difference Between Weather and Climate

Weather	Climate
Changes daily	Changes over many years
Short-term	Long-term
Example: Rain today	Example: Desert climate

4. What is Adaptation?

Adaptation means special features or habits that help animals survive in their environment.

5. Adaptations in Polar Regions

Polar regions are extremely cold and covered with snow.

• Thick fur for warmth
• Layer of fat (blubber)
• White color for camouflage

Example: Polar bear, seal

6. Adaptations in Tropical Rainforests

Tropical rainforests are hot, wet, and dense with tall trees.

• Long limbs for climbing
• Camouflage skin
• Prehensile tails

Example: Monkey, sloth, toucan

7. Adaptations in Desert Regions

Deserts are hot and dry with little rainfall.

• Light-colored skin to reflect heat
• Long legs to avoid ground heat
• Water conservation ability

Example: Camel, desert fox

8. Why Adaptation is Important

Adaptation helps animals:

• Protect themselves from enemies
• Find food easily
• Survive extreme temperatures

9. Summary

Weather tells us the day-to-day condition of the atmosphere, while climate tells us the general weather of a place over many years. Animals have special adaptations that help them survive in different climates such as polar regions, deserts, and rainforests.

Separation of Substances (Handpicking, Filtration & Evaporation)

In our daily life, we often find mixtures of different substances. To make them useful, we need to separate one substance from another. This process is called Separation of Substances.

In Class 6 Chemistry, we study some simple and commonly used separation methods such as Handpicking, Filtration, and Evaporation.

1. Handpicking

Handpicking is the simplest method of separation. In this method, unwanted particles are picked by hand from a mixture.

When is Handpicking Used?

• When the impurities are large in size
• When the quantity of impurities is small
• When the substances can be easily seen

Examples:

• Removing stones from rice or pulses
• Picking rotten fruits from fresh fruits
• Removing plastic pieces from grains

Note: Handpicking is not suitable for very small or dissolved impurities.

2. Filtration

Filtration is a method used to separate an insoluble solid from a liquid using a filter paper or cloth.

The solid that remains on the filter paper is called Residue, and the liquid that passes through it is called Filtrate.

Steps of Filtration

• A filter paper or cloth is placed in a funnel
• The mixture is poured into the funnel
• The liquid passes through, leaving solid behind

Examples:

• Separating tea leaves from tea using a strainer
• Removing sand from water
• Filtering muddy water

Important: Filtration works only when the solid does not dissolve in the liquid.

3. Evaporation

Evaporation is the process in which a liquid changes into vapor to leave behind a solid substance.

This method is mainly used to separate a dissolved solid from a liquid.

How Evaporation Works

• The solution is heated or kept in the open air
• The liquid slowly turns into vapor
• The solid remains behind

Examples:

• Obtaining salt from seawater
• Drying wet clothes
• Recovering sugar from sugar solution

Fact: Evaporation happens faster in hot weather and windy conditions.

Conclusion

Separation of substances helps us obtain useful materials from mixtures. Methods like handpicking, filtration, and evaporation are easy, economical, and widely used in daily life.

Understanding these methods helps students learn how science is applied in real life.