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Many Class 7 students can name every part of a torch and still get stuck on "will the lamp glow?" questions. Usually they have not practised tracing the path of current. This guide covers what Chapter 3 of the new NCERT book asks, a method for predicting any simple circuit, worked examples, and the mistakes that cost marks.
What does Chapter 3 of Class 7 Curiosity cover?
The chapter is called Electricity: Circuits and their Components and it is Chapter 3 of *Curiosity*, NCERT's science textbook for Grade 7, first published in April 2025. The copy on the NCERT site is marked "Reprint 2026-27". It starts with a torch and builds up the parts one at a time:
Electric cell: a portable source of electrical energy with a positive terminal (the metal cap) and a negative terminal (the flat disc).
Battery: two or more cells joined so that the positive terminal of one touches the negative terminal of the next.
Incandescent lamp: a thin wire called the filament gets hot and glows. It does not matter which way round you connect it.
LED: no filament, and current passes in one direction only. The longer leg is positive.
Switch: a device that completes or breaks the circuit. It can go anywhere in the loop.
Conductors and insulators: metals let current pass easily; plastic, rubber, glass and wood do not.
It ends with circuit symbols and diagrams, and warns you to experiment only with cells, never with the mains supply.
Why does a lamp glow only in some arrangements?
The lamp needs a complete path: one terminal of the lamp connected to one terminal of the cell, and its other terminal to the other terminal of the cell. The chapter takes the direction of current to be from the positive terminal to the negative terminal.
So, before you answer any circuit question, put your finger on the positive terminal and trace the wires. If you can travel through the lamp and arrive at the negative terminal without lifting your finger, crossing an open switch or passing through an insulator, the lamp glows.
Worked examples: will it glow?
One cell, one torch lamp. A wire runs from the cell's cap to the metal tip of the lamp. A second wire runs from the metal case of the lamp to the flat end of the cell. Trace: cap, wire, tip, filament, case, wire, flat end. The path is complete, so the lamp glows.
Both wires on the same terminal. Both wires go from the cell's cap, one to the lamp's tip and one to its case. Trace: you go through the filament but come back to the cap, never reaching the negative terminal. No glow.
Two cells and an LED. Positive of the battery to the long leg, negative to the short leg. Complete path, and the current goes the way the LED allows. It glows.
The same LED turned round. The path is still a complete loop, but now current would have to go through the LED the wrong way. No glow. This is the one case where a "complete" circuit still does not work.
A circuit with a safety-pin switch. The safety pin is not touching the second drawing pin. There is an air gap, so the circuit is open. No glow until the pin touches.
Wires with the plastic left on the ends. The plastic is an insulator, so current cannot cross from the wire into the cell terminal. No glow, even though everything looks connected.
What mistakes do students make with circuits?
Engelhardt and Beichner (2004) built a diagnostic test on direct current circuits and gave it to high school and university students. They found students often held several mistaken ideas at once, even after instruction, and that the idea used most often in interviews was that a battery is a constant source of current. It helps to catch such ideas early. The ones that show up most in this chapter:
"The switch makes the electricity." It does not. The cell is the source; the switch only opens or closes the path. The first exercise in the chapter tests exactly this.
"One wire is enough." A single wire from the cell to the lamp gives no loop. You always need a way back.
"An LED is just a small bulb." An incandescent lamp works either way round; an LED does not.
"Cells in a torch can go in any order." The positive end of one must touch the negative end of the next.
How do you draw a circuit diagram correctly?
In the cell symbol, the long line is positive and the short line negative. In the LED symbol, the triangle points the way current can flow. Check every diagram with the same finger trace. A good self-test is the book's question: draw a torch's circuit using only symbols.
A practice routine for this chapter
About 20 minutes a day for one week:
Day 1: Sketch the six set-ups above, predict, then check, with one sentence of reason each.
Day 2: Draw circuit diagrams for every circuit figure in the chapter, using the symbols table.
Day 3: List objects at home as conductors, insulators or "both", as the chapter's project asks. Do not test anything plugged into the wall.
Day 4: Write the answers to the chapter questions from memory, then check against the book. Testing yourself is more effective than rereading: in a study by Roediger and Karpicke (2006), students who practised recalling a passage remembered more a week later than students who reread it.
Day 5: Explain to a parent why a lamp with a broken filament stops the current.
For parents: ask your child to trace the path aloud on any circuit picture. If they cannot say how the current gets back to the cell, that is the gap.
If circuits are hard to picture, seeing one change can help. The Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read, and our post on learning circuits with simulations explains how to use simulations well.
Tonight, sketch a torch circuit from memory and trace the path with your finger before checking the book.
