B1, B2 and B3 are the three identical bulbs connected to a battery of steady e.m.f. with key K closed. What happens to the brightness of the bulbs B1 and B2 when the key is opened?
ABrightness of the bulb B1 increases and that of bulb B2 decreases.
BBrightness of the bulbs B1 and B2 increases.
CBrightness of the bulb B1 decreases and that of bulb B2 increases.
DBrightness of the bulbs B1 and B2 decreases.
How?