Find expressions for the currents in each lightbulb.

+1 vote

Consider the two circuits shown in the figure below in which the batteries are identical. The resistance of each lightbulb is R. Neglect the internal resistance of the batteries.

image

(a) Find expressions for the currents in each lightbulb. (Use the following as necessary: script e for emf and R.)

IA =  
IB =  
IC =  


(b) How does the brightness of B compare with that of C? (Use only ">" or "=" symbols. Do not include any parentheses around the letters or symbols.)


Explain.

(c) How does the brightness of A compare with that of B and of C? (Use only ">" or "=" symbols. Do not include any parentheses around the letters or symbols.)


Explain.

asked Feb 4, 2012 in Physics by Joey33 ~Expert~ (1,216 points)
    

1 Answer

+1 vote
The formula for current is:

i = v / R  (* i=current, v=voltage, R=resistance)

So for part A, we are given E as the voltage, and the lightbulb with resistance R.

Total current in a circuit remains the constant, so we get that:

IA = E/R

 

but for IB and IC since we have to lightbulbs we divide each current by 2 and get:

IB = E/2R    

IC = E/2R

 

part B:

since they both have the same current and voltage they will also have the same brightness, so

B = C

 

Part C.

A will be brighter then B and C because it has more current going through it, and the same amount of voltage, therefore it has greater power and will be brighter.

So,

A > B = C
answered Feb 6, 2012 by kirby ~Expert~ (3,020 points)



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