Q1.
Repeat Activity 4.5 with a battery of 2 cells. What do you notice? For the same duration, does the wire heat up more with one cell or two cells?
Answer
The wire heats up more with two cells. For the same 30 seconds, the amount of heat generated in the experiment with 2 cells is greater.
Why it happens: a battery of two cells drives a larger current through the nichrome wire than a single cell does, and the heat generated depends on the magnitude of the electric current. More current through the same wire for the same time means more electrical energy converted into heat, so the wire ends up hotter.
Altogether, the heat generated in a wire depends on:
- the material of the wire (nichrome heats far more than copper);
- the thickness of the wire;
- the length of the wire;
- the magnitude of the current;
- the duration for which the current flows.
Safety first: the book states plainly that this activity should be carried out strictly under the supervision of a teacher. With two cells the wire gets hotter than before, so touch it only for an instant and never hold it.