For an ideal battery (r = 0 Ohm), closing the switch in the figure (Figure 1) do

Question

For an ideal battery (r = 0 Ohm), closing the switch in the figure (Figure 1) does not affect the brightness of bulb A. In practice, bulb A dims just a little when the switch closes. To see why, assume that the 2.0 V battery has an internal resistance 0.9 Ohm and that the resistance of a glowing bulb is 6.0 Ohm. What is the current through bulb A when the switch is open? Express your answer with the appropriate units. 0.29 A What is the current through bulb A after the switch has closed? Express your answer with the appropriate units. By what percent does the current through A change when the switch is closed?

Explanation / Answer

a) R'=0.9 +6 = 6.9 ohms

I = 2/6.9=0.29 A

b)let's fin dthe resistance

R'= r + R/2= 0.9 + 3= 3.9 ohms

I =2/3.9 = 0.513 A

c)change in percentage = (0.513 - 0.29) /( 0.29) x100=76.834 % apprx

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