BulbA 1.60 3,0? Balb C Bulb & 2. Three light bulbs of fixed resistance 3,0 ? and

Question

BulbA 1.60 3,0? Balb C Bulb & 2. Three light bulbs of fixed resistance 3,0 ? and 6.0 ?. a 90 V battery, and a switch S are connected as shown in the schematic diagram above. The switch S is closed. a. Calculate the current in bulb A. a ov () I-v 3.02 202 2 5.0.2 le 20 I-1.00A bwhichlistify yours brightest?Bube C) Justify your answer By checking the appropriate spaces below, indicate whether the brightness of each light bulb e. Switch S is then opened. Explain your reasoning for each light balb. increases, decreases, or remains the same. i. Bulb A: The brightnessincreases Explanation remains the same increases ii. Bulb B: The brightness Explanation: ins the Bub 3's brightness remant ne saye is in parallel wim Bub C and Bub Claraveit are ane aighnherabecrases Explanuaion if birightness increases remains the same te billbs supply of volhage from -te voltage brrey So will nolonger he bigit

Explanation / Answer

2.

a)

equivalent resistance

Req =3+(1/6 +1/3)-1 =5 ohms

Current through bulb A is

IA =9/5=1.8 A

b)

Current flowing through each light bulb is

IA=1.8 A

IB =1.8*(3/3+6)=0.6 A

IC =1.8-0.6 =1.2 A

The brightness of bulb is directly proportional to square of the current flowing through the bulb. i.e

P=I2R

Therefore Bulb A is brighter than bulb B and bulb C since IA>IC>IB

c)

With Switch s opened ,equivalent resistance

Req=3+6 =9 ohms

Current flowing through each light bulb

IA=IB=9/9 =1 A

IC=0

i)

Therefore Bulb A Brightness decreases with switch s open

ii)

Therefore Bulb B Brightness increases since current flowing through the bulb increases with switch s open

iii)

Therefore Bulb C brightness decreases since no current flows through the bulb as switch is open.

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