Practice_Test_2_with_Solutions

# Practice_Test_2_with_Solutions - Solutions to Practice Test...

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Solutions to Practice Test 2 1. The charge on an electron is –1.602 x 10 -19 C. What is the amount of negative charge in one mole of copper? One mole of copper contains 6.022 × 10 23 (Avogadro number) atoms. Each copper atom contains 29 electrons. Total number of electrons in one mole of copper = 6.022 × 10 23 × 29 = 1.746 × 10 25 The total charge in one mole of copper = 1.746 × 10 25 × -1.602 × 10 -19 = -2.8 × 10 6 C a. -2.8 × 10 6 C 2. If an object is charged positively, A positively charged object contains some excess amount of positive charges over the negative charges. c. it contains more positive charges than negative charges 3. A and B are two small light spheres that can be charged electrically. Which of the following statements is true about these two spheres? A charged object will attract an uncharged object due to polarization of charges in the neutral object c. In order that A and B attract each other, at least one of them must have an excess charge 4. What is the electrostatic force between the electron and the proton if they are 2.5 x 10 -9 m away from each other? A proton and an electron each caries a charge of 1.602 × 10 -19 C 91 9 12 29 2 11 9 10 1.602 10 1.602 10 (2.5 10 ) 3.7 10 N qq Fk r −− ×× × × × × == × = a. 4.1 × 10 -11 N 5. Two positive charges are separated by a distance r and the force of separation between them is F. What is the force of repulsion between them if the distance is increased to 1.8r? r = 2 If F’ is the force between them when the distance between them is 1.8r, then: 22 2 1 '0 . 3 (1.8 ) 3.24 3.24 3.24 F F kk k F rr r === = = d. 0.3F

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6. A charge q 1 = 2 nC is at the origin, a charge q 2 = 3 nC is at x = 1.5 and a charge q 3 = 3 nC is at x = -1.5. What is the force on q 1 due to the other two charges? 1 1.5 -1 -1.5 q 3 = 3 nC q 2 = 3 nC q 1 =2 nC F 13 F 12 Force on q 1 due to q 2 is an repulsive force given by : 999 12 12 22 8 91 0 21 0 31 0 1.5 2.4 10 N qq Fk r ×× × × × == =− × Force on q 1 due to q 3 is an repulsive force given by : 13 13 8 0 1.5 r × × × The total force on q 1 = 2.4 × 10 -8 – 2.4 × 10 -8 = 0 d. 0 7. In question 6, what is the force on q 2 due to the other two charges? 1 1.5 -1 -1.5 q 3 = 3 nC q = 3 nC q 1 =2 nC F 21 F 23 Force on q 2 due to q 1 is an repulsive force given by : 21 8 0 1.5 r × × × Force on q 2 due to q 12 is an repulsive force given by : 23 23 9 0 3 9 10 N r × × ×
The total force on q 2 = 2.4 × 10 -8 + 9.0 × 10 -9 = 3.3 × 10 -8 N a. 3.0 x 10 -8 N i 8. In question 6, what is the force on q 3 due to the other two charges? Proceeding the same way as in 7, force on q 3 due to the other two charges = –3.0 x 10 -8 N i b. –3.0 x 10 -8 N i 9. Which of the following will happen if a positively charged conductor is brought near an insulated neutral conductor?

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## This note was uploaded on 05/01/2011 for the course PHY 2049 taught by Professor George during the Spring '11 term at Edison State College.

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Practice_Test_2_with_Solutions - Solutions to Practice Test...

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