Quiz 13 Last name-- Last 4 St.Id-- 1. Two charges repel each other with force of F=8 x10 N, when they are 200 mm apart. Find the force between the same charges when they are 0.8 m apart . (k=9x109 Nm2/C2): F=kq1 q2/r2 a)16x10-6N b) 12x10-6N c) 0.5x10-6N d) 0.12x10-N e) None of these is true 2. Two charged objects attract each other with a force F. What happens to the force between them if one charge is doubled, the other charge is tripled, and the separation between their centers is reduced to one-fourth its original value? The force is now equal to : a) 16 F b)24 F c)3F/8 d)96 F e) 8F/3 3.How much does it cost to operate a 250 W soldering iron for 8 hours, if energy cost 0.16$ for kWh? P=U/t ; a) 31.8$ b)0.5$ c) 1.5$ d)0.325 e) 0.825 4 . Three 20 ohms resistors are connected in parallel to a 120v battery. What is the equivalent resistance (in ohm) and what is the total current (A) ? 1/R=1/R1 +1/R2 +1/R3 ; I=V/R a) 60; 2 b) 3/20;80 c) 6.7; 12 d) 9; 13.3 e) None of this is true