Brightness of bulb

Electricity and Magnetism Level 2

Two identical light bulbs $X$ and $Y$ , which are rated at $60 \text{ W}$ ; $240 \text{ V,}$ are connected in series to a $240 \text{ V}$ source, as shown in the above diagram. If point A in the circuit is now connected to point B by a piece of copper wire with very low resistance, how will the brightness of each bulb change?

Y will burn brighter and X will not burn. Both X and Y will burn less brightly. X will burn brighter and Y will not burn. Both X and Y will burn brighter.

1 solution

Jonathan Xian Kuan Chee
Dec 30, 2014

By creating an alternative pathway of lower resistance from $A$ to $B$ , the current induced by the e.m.f. source bypasses the route that contains bulb $X$ . This results in almost negligible current passing through bulb $X$ and hence would not light up. Since all the current mainly goes through bulb $Y$ , bulb $Y$ will receive the same voltage as that of the e.m.f. source. Thus, burning the brightest.

Brightness of bulb

1 solution

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