Question

Problem 23.52-MC 8 of 8 The circuit shown (Figure 1) is made with resistors, EACH of which have a maximum power usage of 0.3 W. Assume the following resistor values. Significant Figures Feedback: Your answer 0.067 A was either ounded differently or used a different number of significant figures than required for this part ▼ Part C Figure 1of 1 What is the maximum emf of the battery that can be used to run this circuit? Express your answer using three significant figures Ri Rs Rs Submit X Incorrect; Try Agairn Ro

Answer 1

Power used by R₄ = 0.3 W

Hence current through R₄ is given by the eq.,

I₄² x R₄ = P

$\therefore$ I₄ = sqrt( 0.3 / 65) = 67.93 mA

current through R4= current through the battery= i= 6.793x10^-2 A

now we need to first find the equivalent resistance of the circuit

R1 and R2 are in parallel, so R12=(1/45+ 1/25)^-1 =16.07 ohms.

R5 and R6 are in parallel, so R56= (1/30+ 1/25)^-1=13.636 ohms

now R12, R56, R3 and R4 are in series, so equivalent resistance of circuit=R12+R56+R3 and R4.

Rnet= 16.07 + 13.636 +45+65=139.706 ohms

so the maximum emf= i Rnet

E=6.793x10^-2 (138.706)=9.33

so E=9.49 V = 9.50 V