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PHYSICS 208 EXAMBa OCTOBER 9. 2008

NAME

PLEASE PRiNT

(10) 1. A resistor is attached to a voltage V 0 . As the current flows through the resistor the resistor heats up. doubling its resistance. By what factor does the power dissipated by the resistor change as it heats up?

a. 0.5:b. 0.707: c. 1 (no change): d. 2

Answer:

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(10) 2. A 6 ) resisfor. an 8 resistor and a 24 2 resistor are connected together. What is the minimum resistance that can be produced using all three resistors?

a. 3 Q: b. 4 12: c. 7 12: d. (1/24)12

Answer:______

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4

8

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(10)3. A 2.0mm (2 X m) diameter wire of length 20 m has a resistance of 0.25 2.

Vs hat is the reslst11ty of the w7 ire

a. 0.25 : b. 5 x 10 (2m: c. 16 x I0 2m: d. 3.9 x 108

Answer:

c

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(10) 4. A parallel plate capacitor has a capacitance of 10 microfarad and is charged with a 20 V power supply. The power supply is then removed and a dielectric of dielectric constant 4 is used to fill the space between the plates. The voltage now across the capacitor is

a. zero: b. 5 V: c. 20 V: d. 80 V

Answer:

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(10) 5. In the circuit, the current in the 412 resistor is 3 A. What is the voltage across the 8 12 resistor?

a. 12 V:b.24 V:c.32 V:d.44V

Answer:

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(20) 6. In the circuit shown the capacitors are all initially uncharged, the battery has no internal resistance, and the ammeter is idealized (has no internal resistance). a. Find the reading of the ammeter just after the switch is closed. b. Find the reading of the ammeter after the switch has been closed for a very long time.

(SHOW YOUR WORK NEATLY.)

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(30) 7, The capacitors in the figure are initially uncharged and are connected, as in the diagram, with switch S open. The applied potential Wfference is V, 210 V. a. What is the potential difference Vd? b. What is the potential difference across each capacitor after switch S is closed? (THIS WILL REQUIRE NEAT STEP BY STEP WORK OR YOU WILL GET LOST.)

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