Bright­ness of lamp

Active Kids - - Class Room Discussion -


1. Three pieces of in­su­lated elec­tric wires.

2. Three bulbs.

3. A bat­tery (4.5 volt). 4. A strong pair of scis­sors or wire cut­ter.


1. Scrape the plas­tic at the ends of the three pieces of wire.

2. Con­nect a bulb to a bat­tery, with one end of both wires at­tached to the bat­tery ter­mi­nal and the oth­ers to the two ends of the bulb- holder. Ob­serve the bright­ness of the bulb.

3. Now con­nect two bulbs to the sec­ond bat­tery, as shown in the pic­ture.

What is the re­sult?

The sin­gle bulb in the first case glowed much brighter than the two bulbs in the sec­ond case.

Why did this hap­pen?

As against the first case, where there was just one bulb in the sec­ond case the elec­tric cur­rent that passed through the cir­cuit was be­ing shared by the two bulbs. There­fore, since the en­ergy given out by the bat­tery was be­ing shared in the sec­ond case, the bright­ness with which the bulbs glowed was less­ened.

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