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Unformatted text preview: maini (nm7637) hw8 Shneidman (12108) 1 This printout should have 26 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points Four identical light bulbs are connected ei ther in series (circuit 1) or parallel (circuit 2) to a constant voltage battery with negligible internal resistance, as shown. E Circuit A E Circuit B Compared to the individual bulbs in circuit 1, the individual bulbs in circuit 2 are 1. the same brightness. 2. less than 1 4 as bright. 3. more than 4 times brighter. correct 4. 1 4 as bright. 5. 4 times brighter. Explanation: In circuit 1, the voltage across each light bulb is V = I R = E 4 R R = E 4 , so the power of each bulb in circuit 1 is P 1 = V 2 R = E 2 16 R . In circuit 2, the voltage across each bulb is identical; namely E . Hence the power of each bulb in circuit 2 is P 2 = E 2 R = 1 16 P 1 . We can see that the bulbs in circuit 2 are more than 4 times brighter than the bulbs in circuit 1. 002 (part 2 of 2) 10.0 points If one of the bulbs in circuit 2 is unscrewed and removed from its socket, the remaining 3 bulbs 1. go out. 2. become dimmer. 3. become brighter. 4. are unaffected. correct Explanation: Since the bulbs are parallel, after one of the bulbs is unscrewed, the voltage across each remaining bulb is unchanged, and the brightness is unaffected. 003 (part 1 of 3) 10.0 points A battery with an internal resistance is con nected to two resistors in series. E x y 4 . 2 11 . 4 26 . 5 . 48 A internal resistance What is the emf of the battery? Correct answer: 20 . 208 V. Explanation: maini (nm7637) hw8 Shneidman (12108) 2 E x y r R 1 R 2 I internal resistance Let : R 1 = 11 . 4 , R 2 = 26 . 5 , r = 4 . 2 , and I = 0 . 48 A . The total resistance of the circuit is R total = r + R 1 + R 2 = 4 . 2 + 11 . 4 + 26 . 5 = 42 . 1 , so E = I R total = (0 . 48 A) (42 . 1 ) = 20 . 208 V . 004 (part 2 of 3) 10.0 points What is the magnitude of the potential differ ence V Y X across the terminals y and x of the battery? Correct answer: 18 . 192 V. Explanation: The potential difference across the termi nals of the battery is V Y X = E  I r = 20 . 208 V (0 . 48 A) (4 . 2 ) = 18 . 192 V , or V Y X = I [ R 1 + R 2 ] = (0 . 48 A) (11 . 4 + 26 . 5 ) = 18 . 192 V . Therefore, the magnitude of V Y X is 18 . 192 V. 005 (part 3 of 3) 10.0 points What power is dissipated by the internal re sistance of the battery? Correct answer: 0 . 96768 W. Explanation: The power dissipated by the r = 4 . 2 internal resistance is P internal = I 2 r = (0 . 48 A) 2 (4 . 2 ) = . 96768 W . 006 (part 1 of 3) 10.0 points Consider the circuit a b A 30 V 16 V I 1 4 . 8 3 . 9 I 3 3 . 9 I 2 3 . 4 4 . 5 Find the current through the Amp meter, I 3 ....
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