Question

Hw 28 02 Chapter 28 Problem 28.54 Part A Review What is the current through bulb A when the switch is open? Express yo For an ideal battery (r = 0 Ω), closing the switch in (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 1.50 V battery has an internal resistance r 0.20 2 and that the resistance of a glowing bulb is R-400 Ω. ur answer with the appropriate units. A, open Units Submit Part B What is the current through bulb A after the switch has closed? Express your answer with the appropriate units. Figure A, cloandValue Units < 1of1 Submit Request Answer Part C By what percent does the current through A change when the switch is closed? 1A, closed-1A, open- Submit Request Answer

Answer 1

Part a)

When the switch is open, no current flow through B

Total resistance, R1=r+ R4=0.2+4=4.2 ohms

Current, I=V/R1=1.5 V/4.2 ohms=0.357 A

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Part b)

When switch is closed, Resistance R2= r+ (Ra Rb/Ra+ Rb)

=0.2+(4*4/4+4)=2.2 ohms

Current, I= V/R2=1.5/2.2=0.68 A

Current flowing through bulb A, i= iA/2 =0.34 A (Ans)

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Part c)

Percentage change in current

= (i-iA/i)*100

=(0.357-0.34)/0.357*100 =4.76 % (Ans)

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