Electrical Circuits: Comparing Currents and Power in Parallel and Series Connections, Study notes of Physics

Download Electrical Circuits: Comparing Currents and Power in Parallel and Series Connections and more Study notes Physics in PDF only on Docsity! Q19-4. Two resistors R1 and R2 are hooked to a battery in parallel. R1 is twice as large as R2. How does the current IB from the battery compare to the current I1 though R1? (Hint: IB = I1+ I2.) A) IB = I1 B) IB=2I1 C) IB=3I1 D) IB=4I1 E) None of these. Answer: The voltage across R1 is the same as the voltage across R2, but R1 is twice as large as R2 so I1 is half the size of I2 (since I=V/R, same V, R twice as big means I half as large.) So if I1 = 1A, I2 would be 2A, and Itot=IB = I1 + I2 = 1A + 2A = 3A, which is three times as large as IB. IB=3I1. V R 1 I1 I2 R 2 IB = 2 R2 Q19-7. The three light bulbs A, B, and C are identical. How does the brightness of bulbs B and C together compare with the brightness of bulb A? A) Total power in B+C = power in A. B) Total power in B+C > power in A. C) Total power in B+C < power in A. Answer: If each light bulb has the same resistance R, the series resistance of B and C is 2R. Power P=V2/R. Larger total resistance for the B/C pair means less power. Total power in B+C < power in A. V=12V A B C