Three identical bulbs are connected to a battery as shown.When the circuit is closed by means of the switch S, it is found that a)P,Q and R all will be equally bright b) P will be bright,but Q and R dim explain why?

Asked by Amyra B | 21st Nov, 2013, 10:30: AM

Expert Answer:

Option (b) is correct.
Let the resistance of the bulbs P, Q and R is R'.
Here all the three bulbs are indentical, therefore they would have same resistance R'.
when switch is connected, the current wiil flow from the circuit.
Assume that current flowing from the circuit is I.
This current I will split into I1 and I2.
I = I1 + I2
Current flowing from bulb P = I        Voltage Vp = IR'
Current flowing from bulb Q = I1      Voltage VQ = I1R'
Current flowing from bulb R = I2      voltage VR = I2R'
It is obvious that I1 and I2 would be less than I. Hence the voltages across bulb Q and R would be low than that of bulb P.
Therefore, bulb P would be more bright than bulbs Q and R.

Answered by Komal Parmar | 21st Nov, 2013, 11:46: AM

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