NCERT Solutions for Class 7th Science Chapter 3 Activity 3.2: Let us observe — Electric cell
Book page 25 Updated on2026-09-19
Q1.
Take an electric cell, turn it around and look at it carefully (Fig. 3.2). Do you notice a positive (+) sign and a negative (–) sign marked on the electric cell?
Fig. 3.2, page 25 — an electric cell, with its two terminals marked.
Answer
Yes. Printed on the outer cover of every cell there is a + sign at one end and a – sign at the other end.
These two marks name the two terminals of the cell:
Mark on the cell
Name of the terminal
Short form
+
Positive terminal
+ ve
–
Negative terminal
– ve
Tip: The signs matter a great deal for an LED and for putting cells into a battery in the right order, so never ignore them while making a circuit.
Q2.
Do you also notice that it has a small protruding metal cap on one side and a flat metal disc on the other side?
Answer
Yes — and the two are not decoration; they are the terminals themselves.
Part of the cell
What it looks like
Which terminal it is
Metal cap
A small raised knob sticking out at one end
Positive (+) terminal
Metal disc
A flat metal plate covering the other end
Negative (–) terminal
So even if the printing on a cell has worn away, you can still tell the terminals apart by feeling for the raised cap.
Why it happens: The cap and the disc are the only two metal parts a wire can be joined to. Everything in between is the chemical material of the cell, which turns chemical energy into electrical energy. That is why an electric cell is called a portable source of electrical energy.