NCERT Solutions Curiosity Chapter 4 In-text Questions — How Does a Battery Generate Electricity?
Book page 55 & 56 Updated on2026-09-05
Q1.
Yes, but have you ever wondered what is inside these cells and batteries that produces electricity?
Answer
Inside every cell there are two electrodes of different materials dipped in an electrolyte, and it is the chemical reaction between them that produces the electricity.
Both kinds of cell have the same three parts — two different electrodes and an electrolyte. In a dry cell the electrolyte is a thick moist paste instead of a liquid.
Why the arrangement produces electricity: the two rods must be of different materials. Each reacts differently with the electrolyte — usually a weak acid or a salt solution — and this difference sets up a push that drives current through the outside circuit, from the positive terminal, through the lamp, and back to the negative terminal. Over time the chemicals that take part in the reaction get used up, and the cell then stops working; it is called dead.
Did you know? This is why Galvani's frog leg twitched when copper and iron touched it, and why Volta could still get a current after replacing the frog leg with saltwater-soaked paper. The electricity came from the two metals and the liquid, not from the frog — and that discovery gave us the first battery.
Q2.
Can we also make our own Voltaic cell using easily available materials?
Answer
Yes — a lemon, a copper wire and an iron nail are enough. That is exactly what you build in Activity 4.6.
Electrodes: the copper wire and the iron nail — two different metals, as a Voltaic cell requires.
Electrolyte: the lemon juice, which is a weak acid and helps conduct electricity. A salt solution works just as well.
Container: the lemon itself.
Why several lemons are joined together: one lemon cell gives only a small push — usually not enough to light the LED on its own. Joining five or six of them in a chain, copper of one to the nail of the next, adds their pushes together, and the LED glows.
Try This: repeat it with a potato, a tomato or an orange, and with other pairs of metals — zinc and copper, aluminium and copper, magnesium and copper. Which pair lights the LED most brightly?