Two light bulbs have resistances of 700 ? and 1200 ?. The two light bulbs are co

Question

Two light bulbs have resistances of 700 ? and 1200 ?. The two light bulbs are connected in series across a 120 V line.

(a) Find the current through the 700 ? bulb. (Amps)

Find the current through the 1200 ? bulb. (Amps)

(b) Find the power dissipated in the 700 ? bulb. (Watts)

Find the power dissipated in the 1200 ? bulb. (Watts)

Find the total power dissipated in both bulbs. (Watts)

The two light bulbs are now connected in parallel across the 120 V line.

(c) Find the current through the 700 ? bulb. (Amps)

Find the current through the 1200 ? bulb. (Amps)

(d) Find the power dissipated in the 700 ? bulb. (Watts)

Find the power dissipated in the 1200 ? bulb. (Watts)

Find the total power dissipated in both bulbs. (Watts)

Explanation / Answer

a)

In series ,equivalent resistance

R=700+1200=1900 ohms

Total Current flowing

I=V/R =120/1900 =0.063 A

Current through each resistor is

I700=0.063 A

I1200=0.063 A

b)

Power dissipated is given by

P=I2R

so

P700=0.0632*700=2.79 Watts

P1200=0.0632*1200=4.79 Watts

Total Power

P=0.063162*1900=7.58 Watts

c)

equivalent resistance

1/R =1/700 +1/1200

R=442.1 ohms

Current through each bulb

I700=120/700=0.17 A

I1200=120/1200=0.1 A

d)

Power dissipated is

P700=0.172*700 =20.57 Watts

P1200=0.12*1200=12 Watts

Total Power

P=(0.17+0.1)2*442.1 =32.57 Watts

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.