This MCQ module is based on: Electric Cells, Bulbs and Simple Circuits
TOPIC 7 OF 46
Electric Cells, Bulbs and Simple Circuits
🎓 Class 7
Science
CBSE
Theory
Ch 3 — Electricity: Circuits and Their Components
⏱ ~14 min
🌐 Language: [gtranslate]
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[myaischool_lt_science_assessment grade_level="class_7" science_domain="physics" difficulty="basic"]
Electricity Around Us
On a bright summer morning, Nihal and his family took a trip to the Bhakra Nangal Dam — one of India's largest hydroelectric power stations on the river Sutlej. As Nihal watched the mighty spillways release rushing water, a guide explained that this very water is used to rotate huge turbines that generate electricity which reaches lakhs of homes, schools, and factories across several states.
On the way back, Nihal began looking around with new eyes. From the fan that cooled him in the car to the phone his sister used to click photos — everything seemed to need electricity. He started a list of all the things electricity does for us.
Think about it: Imagine a full day without electricity. No fans, no lights, no mobile charging, no fridge, no traffic signals. How would your routine change?
Everyday Uses of Electricity
Cooking
Electric kettle, mixer-grinder, induction cooktop, oven
Lighting
Tube lights, bulbs, LED lamps, street lights
Transport
Electric trains, metros, lifts, e-vehicles
Heating / Cooling
Fans, ACs, refrigerators, heaters, geysers
Entertainment
TV, radio, music systems, gaming devices
Communication
Mobile phones, internet routers, computers
3.1 The Electric Cell
Most of the electricity we use at home travels long distances through wires from power stations. But many small devices — a wall clock, a torch, a TV remote, a wrist watch — run on their own small electric cell. These portable power sources are what we call dry cells or batteries.
Parts of a Dry Cell
- A small metal cap at the top — this is the positive terminal (+).
- A zinc case covering the rest of the cell — this forms the negative terminal (−).
- A plastic or paper jacket printing the brand, voltage, and symbols.
Remember the Symbol:
In circuit drawings a cell is shown as two parallel lines: a long line = positive (+) terminal, and a short, thicker line = negative (−) terminal.
In circuit drawings a cell is shown as two parallel lines: a long line = positive (+) terminal, and a short, thicker line = negative (−) terminal.
Different Shapes and Sizes of Cells
| Type | Shape / Size | Used In |
|---|---|---|
| AA cell | Cylindrical, medium | Remotes, wall clocks, toys |
| AAA cell | Cylindrical, slimmer | TV remotes, small torches |
| Button cell | Flat, coin-like | Wrist watches, calculators, hearing aids |
| 9 V cell | Rectangular | Smoke alarms, multimeters |
🔍 Activity 3.1 — Observe a Dry CellL2 Understand
🤔 Predict first: Which end of the cell do you think is marked '+'? Why do you think makers put both + and − signs on every cell?
- Take any used dry cell (AA or AAA) carefully.
- Locate the small metal cap on one end and the flat end on the other.
- Look for printed markings: '+' near the cap, '−' near the flat end, and the voltage (e.g. 1.5 V).
- Note the shape, length, and any warning symbols like 'Do not dispose in fire'.
What you should notice: The metal cap side is marked '+', the other side is '−'. The voltage is usually 1.5 V. Every device that uses cells has markings inside to show how the cells should be inserted so that + and − match correctly.
3.2 The Electric Bulb
An electric bulb is a simple device that turns electricity into light. Look at a bulb closely (always a switched-off one) and you will see several parts.
Parts of an Electric Bulb
- Filament: a very thin coiled wire made of tungsten. It glows brightly when current passes through it.
- Glass bulb: a sealed glass envelope filled with an inert gas (argon/nitrogen) or sometimes kept as a vacuum. This prevents the filament from burning out.
- Two terminals at the base: one at the tip, and one on the side of the metal cap. Current enters through one terminal and leaves through the other after flowing through the filament.
Fused bulb: When the thin tungsten filament breaks, the path for current is cut. Such a bulb is called a fused bulb. Current cannot flow and the bulb does not glow, even if everything else is perfect. You can often hear a slight rattle when you shake a fused bulb.
🔍 Activity 3.2 — Examine a BulbL2 Understand
🤔 Predict first: If you break the glass of a working bulb but keep the filament safe, will it still glow when connected to a cell? Why or why not?
- Carefully hold a small torch bulb (never a mains bulb).
- Look through the glass and locate the thin zig-zag filament.
- Identify the two terminals — one at the tip, one on the side of the metal cap.
- Compare it with a fused bulb (filament broken). Notice the difference.
The filament is a thin coiled wire supported between two metal wires. The glass protects it and also keeps out oxygen so the wire does not burn. A fused bulb will have a broken filament — the two ends no longer join.
3.3 Connecting a Cell and a Bulb — The Simple Circuit
A bulb by itself will not glow. Even a cell by itself does nothing. But when we join them with wires in the right way, magic happens — the bulb lights up. This closed loop is called an electric circuit.
🔬 Activity 3.3 — Build Your First CircuitL3 Apply
🤔 Predict first: If you leave one end of the wire disconnected from the cell, will the bulb still glow?
- Take one cell, a torch bulb, and two pieces of insulated copper wire (with the plastic removed at the ends).
- Join one wire from the + terminal of the cell to one terminal of the bulb.
- Join the second wire from the other terminal of the bulb to the − terminal of the cell.
- Observe the bulb. Now disconnect one wire and observe again.
Closed circuit: Both wires connected → the bulb glows. The loop is complete and current flows.
Open circuit: One wire disconnected → the bulb does NOT glow. The loop is broken and current cannot flow.
Open circuit: One wire disconnected → the bulb does NOT glow. The loop is broken and current cannot flow.
| State of Circuit | Path | Current | Bulb |
|---|---|---|---|
| Closed | Complete loop | Flows | Glows |
| Open | Broken/disconnected | Does not flow | Does NOT glow |
LEDs — The Modern Light Source
You have probably seen tiny, bright lights on mobile chargers, fairy lights, torches, and TVs. These are LEDs — Light Emitting Diodes.
- An LED has two legs: the longer leg is the positive (+) end and the shorter leg is the negative (−) end.
- It glows only when connected the correct way — the long leg must go to the + terminal of the cell.
- LEDs use much less electricity than ordinary bulbs.
- They are brighter for the same amount of current, and last many years longer.
⚡ Interactive: Build a Simple Circuit L3 Apply
Click the wires to connect/disconnect them. When the loop is complete, the bulb glows!
Tip: a wire is "connected" when it turns solid orange. All 5 wires must be connected for the bulb to glow.
📋 Competency-Based Questions
Riya connects a dry cell to a bulb using two wires. The bulb glows brightly. Then she removes one wire from the cell but keeps everything else in place.
Q1. L2 Understand After Riya removes the wire, what happens to the bulb?
Answer: C. Removing one wire breaks the closed loop. With an open circuit, no current flows, so the bulb stops glowing.
Q2. L1 Remember Fill in the blank: In a dry cell, the metal cap is the ______ terminal and the zinc case is the ______ terminal.
Answer: positive (+); negative (−).
Q3. L4 Analyse A torch suddenly stops working. When checked, the cell is new and the wires are fine, but shaking the bulb makes a rattling sound. What is the most likely reason? (Short Answer)
Answer: The bulb is fused — its filament has broken (the rattle is the broken tungsten inside). Since the filament is the path for current in the bulb, it does not glow. Replacing the bulb will fix the torch.
Q4. L2 Understand True or False: An LED glows no matter which way it is connected to the cell. Justify.
Answer: False. An LED is polarity sensitive. It glows only when its longer leg is connected to the positive terminal and shorter leg to the negative terminal. If connected the wrong way, it will not glow.
Q5. L6 Create HOT: Design a simple battery-operated night lamp for your study table using a cell, an LED, and a wire. Draw the circuit and explain.
Hint: Connect the long leg of the LED to the + terminal of the cell and the short leg to the − terminal through a wire. The LED will glow and act as a small night lamp. For safety, use a 1.5 V cell and test before regular use.
🔗 Assertion–Reason Questions
Assertion (A): A bulb does not glow if only one wire connects it to a cell.
Reason (R): Electric current needs a closed, complete loop to flow.
Answer: A. With only one wire the loop is incomplete — so no current flows and the bulb does not glow. The Reason explains why.
Assertion (A): A fused bulb can be made to work again by connecting it to a stronger cell.
Reason (R): The filament of a fused bulb is broken, so no current can flow through it.
Answer: D. Assertion is false — a stronger cell cannot repair a broken filament. Reason is true and is actually the cause for why the fused bulb can never glow until replaced.
Assertion (A): The longer leg of an LED is connected to the positive terminal of the cell.
Reason (R): LEDs work only when connected with correct polarity.
Answer: A. LEDs are polarity sensitive. The longer leg is the + end and must be joined to the + terminal of the cell. The Reason correctly explains the Assertion.
Frequently Asked Questions — Electric Cells, Bulbs and Simple Circuits
What does the topic 'Electric Cells, Bulbs and Simple Circuits' cover in Class 7 Science?
The topic 'Electric Cells, Bulbs and Simple Circuits' is part of NCERT Class 7 Science Chapter 3 — Electricity: Circuits and their Components. It covers the key ideas of electric cell, bulb, filament, terminals, simple circuit, electric current, torch, battery, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Electric Cells, Bulbs and Simple Circuits' important for Class 7 NCERT Science?
'Electric Cells, Bulbs and Simple Circuits' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 3 — Electricity: Circuits and their Components — introduces electric cell and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Electric Cells, Bulbs and Simple Circuits?
The key concepts in 'Electric Cells, Bulbs and Simple Circuits' for Class 7 Science are: electric cell, bulb, filament, terminals, simple circuit, electric current, torch, battery. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 3 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Electric Cells, Bulbs and Simple Circuits taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Electric Cells, Bulbs and Simple Circuits' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 3 — Electricity: Circuits and their Components — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of electric cell can Class 7 students observe at home?
Class 7 students can observe electric cell at home in many simple ways linked to 'Electric Cells, Bulbs and Simple Circuits'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 3 — Electricity: Circuits and their Components. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Electric Cells, Bulbs and Simple Circuits' connect to other chapters of Class 7 Science?
'Electric Cells, Bulbs and Simple Circuits' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of electric cell appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 3 — Electricity: Circuits and their Components — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
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