A combination of two or more cells connected together

What does a switch do in an electrical circuit?

It either completes or breaks the circuit

What is the direction of electric current in a closed circuit?

From negative to positive terminal

From positive to negative terminal

What is an electrical insulator?

A material through which current flows easily

A material through which current cannot flow

A material that stores electricity

A material that converts electricity to heat

What is the purpose of plastic or rubber covering on electric wires?

To protect people from electric shocks

What is a circuit diagram?

A map of a building's electrical system

A representation of an electrical circuit using symbols

For an LED lamp to glow — how must it be connected?

Positive terminal of LED to negative terminal of battery

Any terminal of LED can connect to any terminal of battery

Positive terminal of LED to positive terminal of battery and negative to negative

LEDs do not require specific connections

Why does an incandescent lamp sometimes not glow even when connected to a working cell?

The filament is broken — a broken filament stops current flow preventing the lamp from glowing

What is the key difference between an incandescent lamp and an LED in terms of polarity?

Only incandescent lamps have polarity

Only LED has polarity — current passes through LED in one direction only while incandescent lamp glows regardless of which terminal connects to positive

Why is copper the most commonly used metal for electrical wires despite silver and gold being better conductors?

Copper is used for its comparatively lower cost and abundant supply while maintaining sufficient conductivity

What is the difference between an open circuit and a closed circuit?

Open circuit has more components

In a closed circuit the path is complete and current flows — in an open circuit there is a gap preventing current flow

Closed circuits have more cells

Why is it dangerous to touch electrical switches or plugs with wet hands?

Water conducts heat not electricity

The human body is a conductor of electricity and water increases conductivity creating a path for current to pass through the body causing severe injury

Only damaged switches are dangerous when wet

What is the difference between DC (Direct Current) from batteries and AC (Alternating Current) from power plants?

DC from batteries powers small devices and flows in one direction while AC from power plants can run larger appliances and changes direction periodically

DC and AC are essentially the same

In Activity 3.3 when cells are placed in reverse order in a torch — why does the lamp not glow?

Reversing cell direction breaks the proper series connection — the positive-to-negative sequence required to form a working battery is disrupted — preventing current flow

Why does current flow through LED in only ONE direction but through an incandescent lamp in BOTH directions?

Incandescent lamps are more powerful

LED is a semiconductor device with an inherent directional property while the incandescent lamp's filament is just a resistive wire that heats up regardless of current direction — demonstrating the difference between passive and active electronic components

LEDs are smaller than incandescent lamps

Incandescent lamps have more terminals

How does increasing the number of cells in a battery affect the circuit's performance?

More cells connected in series provide more energy to the circuit for longer time and may increase the intensity of the output — each cell contributes to the total voltage

Cells in series cancel each other

Why do international organisations like IEC and IEEE create standard electrical symbols for circuit diagrams?

Standard symbols allow engineers and scientists from different countries to understand and replicate electrical circuits without language barriers — enabling global scientific and industrial collaboration

Standard symbols are only used in schools

If a circuit has two lamps connected in series (as in Fig. 3.17) and one lamp's filament breaks — why does the other lamp also not glow?

A series circuit has only one path for current — a break in the filament of one lamp creates a gap in the single path stopping current flow to ALL components in the series

Both filaments are always connected

What does the concept of a 'closed circuit' reveal about the nature of electric current?

Current can flow in open circuits too

Electric current is a continuous flow that requires an unbroken loop — if any part of the path is disconnected the entire flow stops — demonstrating that electricity behaves as a system not as isolated segments

Open and closed circuits function the same way

Current flows only in straight lines

How does the evolution of lighting technology from incandescent lamps to LEDs illustrate the principle of improving efficiency?

Incandescent lamps waste energy as heat from a glowing filament — LEDs emit light directly from semiconductor material with far less heat loss — the same circuit improvement represents decades of applied physics and materials science

Incandescent lamps are brighter

A student makes a circuit tester. They touch free wire ends to objects and find that metal spoon and key make the lamp glow while rubber eraser and wooden block do not. What principle explains these results and why is this practically important?

The objects have different weights

Metals are conductors because they have free electrons that can carry current while non-metals like rubber and wood are insulators that do not have free electrons — this determines what materials are safe to use in electrical devices and which provide protection

The brightness of the lamp depends on object colour

All materials eventually conduct electricity

How does the concept of electrical safety (insulation wet hands caution with damaged wires) reflect a deeper understanding of human biology and physics?

Safety rules are just precautions

The human body is a conductor — this is biology — and electricity follows all available conducting paths — this is physics — safety rules exist because current passing through the heart can be fatal — making electrical safety a life-science application

Safety is only relevant for professional electricians

Electrical safety only matters for high voltage

NCERT Solutions Class 7 Science Chapter 3 – Electricity: Circuits and their Components

Name: Electricity: Circuits and their Components – Class 7 Science
Uploaded: 2026-07-23T02:21:57+00:00
Description: This chapter explores how electricity is generated, conducted, and used in daily life. Students learn about electric cells, batteries, lamps, switches, circuits, conductors, and insulators through simple experiments and activities.

Class 7 Science

Last Updated: 23 July 2026

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Chapter Introduction

This chapter explores how electricity is generated, conducted, and used in daily life. Students learn about electric cells, batteries, lamps, switches, circuits, conductors, and insulators through simple experiments and activities.

हिंदी में (Hindi)

इस अध्याय में यह बताया गया है कि बिजली कैसे उत्पन्न होती है, बहती है और हमारे दैनिक जीवन में इसका उपयोग कैसे होता है। विद्यार्थी इलेक्ट्रिक सेल, बैटरी, बल्ब, स्विच, सर्किट, चालक और अचालक पदार्थों को प्रयोगों और गतिविधियों के माध्यम से सीखते हैं।

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Important Points

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Practice MCQ Questions (28 questions)

Q1. What is an electric cell?

Q2. How many terminals does an electric cell have?

Q3. What is a battery?

Q4. In a battery how are cells connected?

Q5. What is the thin wire inside an incandescent lamp called?

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Frequently Asked Questions (FAQ)

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Tough Words (Glossary)

hydroelectric

Meaning: related to producing electricity using moving water

अर्थ: जलविद्युत से संबंधित

"Bhakra Nangal has a huge hydroelectric power house."

powerhouse

Meaning: a building where electricity is generated

अर्थ: विद्युतगृह/पावर हाउस

"We toured the powerhouse to see how electricity is made."

generate

Meaning: to make or produce

अर्थ: उत्पन्न करना

"Falling water can generate electricity."

Sutlej

Meaning: a major river flowing through north India and Pakistan

अर्थ: सतलुज (नदी का नाम)

"The train runs along the Sutlej river."

Shivalik

Meaning: the outermost range of the Himalayas

अर्थ: शिवालिक (हिमालय की बाहरी श्रेणी)

"They rode through the Shivalik hills."

astonishment

Meaning: great surprise

अर्थ: आश्चर्य

"To their astonishment, the list kept growing."

organise

Meaning: to arrange in order

अर्थ: वर्गीकरण/व्यवस्थित करना

"They organised the uses under headings."

appliance

Meaning: a device or machine used at home

अर्थ: घरेलू उपकरण

"A microwave is a common kitchen appliance."

escalator

Meaning: a moving staircase

अर्थ: चलती सीढ़ी/एस्केलेटर

"The mall has a long escalator."

immersion rod

Meaning: a device that heats water when immersed

अर्थ: इमर्शन रॉड/पानी गर्म करने की छड़

"Use an immersion rod carefully."

socket

Meaning: a wall outlet for an electric plug

अर्थ: सॉकेट/प्लग छिद्र

"Plug the charger into the socket."

portable

Meaning: easy to carry

अर्थ: पोर्टेबल/सहज ले जाने योग्य

"Cells are portable sources of electricity."

generator

Meaning: a machine that produces electricity

अर्थ: जनरेटर/विद्युतजनित्र

"Even small generators can be dangerous."

torchlight

Meaning: a handheld light; flashlight

अर्थ: टॉर्च/हाथ से पकड़ने वाली रोशनी

"He switched on the torchlight in the dark."

slide (a switch)

Meaning: to move a switch smoothly to another position

अर्थ: स्विच को सरकाना

"Slide the switch to turn the lamp on."

compartment

Meaning: a separate section

अर्थ: खाना/डिब्बा/खंड

"Open the cell compartment of the torch."

reverse

Meaning: to change to the opposite direction or order

अर्थ: उलट देना/उलटा करना

"Reverse the direction of one cell."

arrangement

Meaning: the way things are placed

अर्थ: विन्यास/व्यवस्था

"Only the correct arrangement makes the lamp glow."

battery

Meaning: two or more cells joined together

अर्थ: बैटरी

"This toy car runs on a battery."

incandescent

Meaning: glowing because it is hot

अर्थ: तप्त‑दीप्त/दीप्तिमान

"An incandescent bulb has a hot filament."

filament

Meaning: very thin wire inside a bulb that glows

अर्थ: फिलामेंट/सूक्ष्म तार

"The filament breaks when a bulb fuses."

terminal

Meaning: the point where a wire or device connects

अर्थ: ध्रुव/टर्मिनल

"Connect the wire to the positive terminal."

protruding

Meaning: sticking out

अर्थ: उभरा हुआ/निकला हुआ

"The protruding metal cap is the positive terminal."

diode

Meaning: a device that allows current in one direction only

अर्थ: डायोड

"An LED is a light‑emitting diode."

LED (Light Emitting Diode)

Meaning: a diode that emits light when current flows

अर्थ: एलईडी (प्रकाश उत्सर्जक डायोड)

"LED lamps save energy."

holder

Meaning: a part that supports or keeps something in place

अर्थ: होल्डर/धारक

"Fix the lamp in the holder."

insulate

Meaning: to cover so electricity or heat does not pass

अर्थ: रोधक आवरण करना/इन्सुलेट करना

"Wires are insulated with plastic."

electrical tape

Meaning: sticky tape used to cover or join wires safely

अर्थ: इलेक्ट्रिकल टेप/विद्युत टेप

"Use electrical tape to attach the wires."

predict

Meaning: to say what you think will happen

अर्थ: अनुमान लगाना/भविष्यवाणी करना

"Predict if the lamp will glow."

observation

Meaning: what you see or notice

अर्थ: अवलोकन/देखा‑भाला निष्कर्ष

"Record your observation in the table."

electrical circuit

Meaning: a complete path for current to flow

अर्थ: विद्युत परिपथ/सर्किट

"The lamp glows only in a closed circuit."

current (electric)

Meaning: the flow of electric charge

अर्थ: विद्युत धारा

"Current flows from the cell through the lamp."

fused (lamp)

Meaning: stopped working due to a broken filament

अर्थ: फ्यूज़ (बल्ब) / जला हुआ

"Replace the fused bulb."

interchange

Meaning: to swap positions

अर्थ: आपस में बदलना/अदला‑बदली करना

"Interchange the LED wires and see."

rotate

Meaning: to turn around a point

अर्थ: घुमाना/भ्रमण कराना

"Rotate the safety pin to close the switch."

cardboard

Meaning: stiff, thick paper

अर्थ: गत्ता

"Mount the switch on cardboard."

drawing pin

Meaning: short pin with a wide head for fixing paper

अर्थ: ड्रॉइंग पिन/कुंडी पिन

"Fix the wire with a drawing pin."

safety pin

Meaning: a pin with a clasp for fastening

अर्थ: सेफ्टी पिन

"A safety pin can act as a switch lever."

gap

Meaning: an opening or space between two parts

अर्थ: अंतर/खाली जगह

"The gap keeps the circuit open."

closed (circuit)

Meaning: with a complete path for current

अर्थ: बंद (परिपथ)

"In a closed circuit the lamp lights."

open (circuit)

Meaning: with a broken path so current can't flow

अर्थ: खुला (परिपथ)

"An open circuit stops the current."

symbol

Meaning: a simple sign used to represent something

अर्थ: प्रतीक

"Draw the symbol for a cell."

diagram

Meaning: a simple drawing that explains something

अर्थ: आरेख/चित्र

"Make a circuit diagram using symbols."

standard

Meaning: accepted or agreed upon by many

अर्थ: मानक

"We use standard circuit symbols."

conductor

Meaning: a material that allows electricity to pass

अर्थ: चालक पदार्थ

"Metals are good conductors."

insulator

Meaning: a material that does not allow electricity to pass

अर्थ: रोधक पदार्थ

"Rubber is an insulator."

tester

Meaning: a simple setup to check something

अर्थ: परीक्षक/टेस्टर

"Use the lamp tester to check conductors."

momentarily

Meaning: for a very short time

अर्थ: क्षणभर के लिए

"Touch the wire ends momentarily."

aluminium foil

Meaning: thin sheets of aluminium metal

अर्थ: एल्युमिनियम फॉइल/पतली चादर

"Aluminium foil conducts electricity."

ceramic

Meaning: hard, non‑metal material often used as insulator

अर्थ: सिरेमिक/मिट्टी‑आधारित पदार्थ

"Switches use ceramic parts."

abundant

Meaning: present in large quantities

अर्थ: प्रचुर/बहुत मात्रा में

"Copper is abundant enough for wires."

insulation

Meaning: protective non‑conducting covering

अर्थ: इन्सुलेशन/रोधक आवरण

"Damaged insulation is dangerous."

shock (electric)

Meaning: a sudden jolt from electricity

अर्थ: बिजली का झटका

"Wet hands increase shock risk."

alternating current (AC)

Meaning: electricity that changes direction repeatedly

अर्थ: परिवर्ती धारा (ए.सी.)

"Wall sockets provide alternating current."

direct current (DC)

Meaning: electricity that flows in one direction only

अर्थ: दिष्ट धारा (डी.सी.)

"Batteries supply direct current."

series (connection)

Meaning: end‑to‑end connection increasing voltage

अर्थ: श्रृंखला संयोजन

"Two cells in series can light an LED."

terminal cap

Meaning: the metal cap end of a cell

अर्थ: ध्रुव कैप/धातु टोपी

"The terminal cap touches the spring."

spring side

Meaning: the side with the metal spring in a holder

अर्थ: स्प्रिंग वाला सिरा

"Place the negative end on the spring side."

polarity

Meaning: the property of having positive or negative ends

अर्थ: ध्रुवीयता

"LEDs must be connected with correct polarity."

glow

Meaning: to give out light steadily

अर्थ: प्रकाशमान होना/चमकना

"Does the lamp glow now?"

swirl

Meaning: to move something in small circles

अर्थ: घुमाना/हल्का घोलना

"Swirl the solution gently."

comply

Meaning: to act according to a rule or request

अर्थ: पालन करना

"Comply with safety warnings."

hazard

Meaning: a danger or risk

अर्थ: जोखिम/खतरा

"Exposed wires are a hazard."

indicator (lamp)

Meaning: a small light that shows a device’s status

अर्थ: सूचक लैम्प

"The indicator lamp shows power on."

wire stripper

Meaning: a tool to remove insulation from wires

अर्थ: तार छीलने का औज़ार

"Use a wire stripper to expose the copper."

connect

Meaning: to join together

अर्थ: जोड़ना/कनेक्ट करना

"Connect the cell to the lamp."

disconnect

Meaning: to separate a connection

अर्थ: अलग करना/डिस्कनेक्ट करना

"Disconnect the battery before repair."

component

Meaning: a part of a larger system

अर्थ: घटक/अवयव

"A switch is a circuit component."

diagrammatic

Meaning: shown by a simple drawing

अर्थ: आरेखीय

"Make a diagrammatic representation."

representation

Meaning: a way of showing something

अर्थ: निरूपण/प्रस्तुतीकरण

"Use symbols for clear representation."

industry

Meaning: businesses that make products or services

अर्थ: उद्योग

"Standard symbols help industry communicate."

electrotechnical

Meaning: relating to electrical technology

अर्थ: विद्युत‑प्रौद्योगिकीय

"IEC means International Electrotechnical Commission."

commission

Meaning: an official group that manages something

अर्थ: आयोग

"The commission sets safety standards."

institute

Meaning: an organisation for education or standards

अर्थ: संस्थान

"ANSI is a standards institute."

materials

Meaning: substances things are made of

अर्थ: पदार्थ/सामग्री

"Different materials conduct differently."

convenient

Meaning: easy and practical to use

अर्थ: सुविधाजनक

"Batteries make portable lights convenient."

abbreviation

Meaning: a shortened form of a word

अर्थ: संक्षेप

"LED is an abbreviation for Light Emitting Diode."

label

Meaning: to mark with a name or symbol

अर्थ: लेबल लगाना/चिह्नित करना

"Label the battery terminals ‘+’ and ‘–’."

ignite (metaphorically)

Meaning: to start or light up (an idea or lamp)

अर्थ: प्रज्वलित करना/जलाना

"Close the switch to ignite the lamp."

precaution

Meaning: something done to prevent harm

अर्थ: सावधानी

"Read all safety precautions first."

pair (of cells)

Meaning: two items used together

अर्थ: जोड़ी

"A pair of cells is needed for the LED."

faulty

Meaning: not working correctly

अर्थ: खराब/दोषपूर्ण

"The lamp won’t glow because the wire is faulty."

identify

Meaning: to find out or recognise

अर्थ: पहचानना

"Identify conductors with a tester."

justify

Meaning: to give reasons to support an answer

अर्थ: युक्तिसंगत ठहराना/तर्क देना

"Justify why the lamp did not glow."

disrupted

Meaning: stopped or disturbed

अर्थ: बाधित/विच्छिन्न

"Power supply was disrupted for two days."

rechargeable

Meaning: able to be filled with energy again

अर्थ: रीचार्ज होने योग्य

"Phones use rechargeable batteries."

abide

Meaning: to follow or obey

अर्थ: पालना करना/मानना

"Always abide by safety rules."

exposed (wire)

Meaning: without protective covering

अर्थ: नंगा/उघड़ा

"Never touch an exposed wire."

precise

Meaning: exact and accurate

अर्थ: सटीक/यथार्थ

"Draw a precise circuit diagram."

observe

Meaning: to watch carefully

अर्थ: ध्यान से देखना/अवलोकन करना

"Observe which connections make it glow."

sequence

Meaning: a particular order of things

अर्थ: क्रम/अनुक्रम

"Follow the sequence of steps."

manual (adj.)

Meaning: done by hand; not automatic

अर्थ: हस्तचालित/हाथ से किया गया

"Make a manual switch using a safety pin."

caution

Meaning: care taken to avoid danger

अर्थ: चेतावनी/सावधानी

"Caution: do not use wall power in experiments."