Light Bulbs in Series and in Parallel. Two light bulbs have resistances of 600 a

Question

Light Bulbs in Series and in Parallel. Two light bulbs have resistances of 600 and 1100 . The two light bulbs are connected in series across a 130 V line. (a) Find the current through the 600 bulb. A Find the current through the 1100 bulb. A (b) Find the power dissipated in the 600 bulb. W Find the power dissipated in the 1100 bulb. W Find the total power dissipated in both bulbs. W The two light bulbs are now connected in parallel across the 130 V line. (c) Find the current through the 600 bulb. A Find the current through the 1100 bulb. A (d) Find the power dissipated in the 600 bulb. W Find the power dissipated in the 1100 bulb. W Find the total power dissipated in both bulbs. W

Explanation / Answer

The two light bulbs are connected in series across a 130 V line

Equivalent resistance = 600+1100 = 1700

current, I = V/R = 130/1700= 0.0765 Amp

current through the 600 bulb = 0.0765 Amp .

and the current through the 1100 bulb  = 0.0765 Amp

power dissipated in the 600 bulb = I2R = 0.07652*600= 3.5 Watt

power dissipated in the 1100 bulb = I2R = 0.07652*1100= 6.43 Watt

total power dissipated in both bulbs. = 3.5+6.43 =9.84 Watt

The two light bulbs are now connected in parallel across the 130 V line.

Now Req = 600*1100/(600+1100) =388.23

I = V/R = 130/388.23 = 0.335 Amp

current through the 600 bulb = 130/600= 0.2167 Amp .

and the current through the 1100 bulb = 130/1100= 0.1182 Amp .

power dissipated in the 600 bulb = I2R = 0.21672*600= 28.17 Watt

power dissipated in the 1100 bulb = I2R =0.11822*1100= 15.36 Watt

total power dissipated in both bulbs. = 28.17+15.36 = 43.53 Watt

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