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PHYS 100 Introductory Physics Sample Exam 3 Formulas: Charge of 1 electron - 1.6 x 10 -19 Coulomb Charge of 1 proton 1.6 x 10 -19 Coulomb Electric Field Force Charge Electric Potential Current Electric Potential Energy Charge Voltage Resistance Power Current x Voltage Section A: All questions in this section are mandatory. 1. One difference between moving and stationary charges is that a. Moving charges exert only magnetic forces, while stationary charges exert both electric and magnetic forces. b. Moving charges exert both electric and magnetic forces, while stationary charges exert only electric forces. c. Moving charges exert only magnetic forces, while stationary charges exert only electric forces. d. Moving charges exert both electric and magnetic forces, while stationary charges exert neither electric nor magnetic forces. 2. What does a neutral atom become if it loses an electron? a. b. c. d. A superconductor A negatively charged ion A positively charged ion It stays neutral 3. Two 20-Ohm resistances are connected in series. The total resistance in the circuit is a. b. c. d. equal to 20 Ohms less than 20 Ohms greater than 20 Ohms it depends on the voltage 4. A simple circuit is shown. How much current is flowing in this circuit? a. b. c. d. 12 Amperes 2.5 Amperes 360 Amperes 0.4 Amperes 12 Volt Battery 30 Ohm Resistance 5. What is the direction of current flow in the circuit of question #4 above? a. b. c. d. Counter Clockwise Clockwise Both a and b Cannot be determined from the given information 6. Electromagnetic induction occurs in a coil when there is a change in a. b. c. d. voltage in the coil the coil’s polarity electric field intensity in the coil magnetic field intensity in the coil 7. A 120-Volt outlet has a 20-Ampere fuse connected in series with it. What is the maximum power that can be delivered by this outlet? a. b. c. d. 2400 Watts 120 Watts 6 Watts 1200 Watts 8. A neutral atom has equal number of a. b. c. d. protons and neutrons electrons and protons electrons and neutrons none of these 9. A +2 C charge is brought to a position that is midway between a -3 C charge and a -2 C charge. If the negative charges were fixed (unable to move), in what direction would the positive charge go? a. b. c. d. Up (away from both charges). Down (away from both charges). Right (toward the -2 C charge). Left (toward the -3 C charge). +2 C -3 C -2 C 10. Which of the following is a unit of electric charge? a. Coulomb b. Volt c. Ohm d. Ampere 11. If a steady magnetic field exerts a force on a moving charge, that force is directed a. b. c. d. perpendicular to the direction of the field in the direction of motion of the charge in the direction of the field opposite to the direction of the field 12. A quantity that measures opposition to the flow of charge is a. current b. voltage c. resistance d. electric field 13. A device that transforms mechanical energy into electrical energy is a a. magnet b. transformer c. generator d. motor 14. Which of the following materials conduct electricity with the greatest amount of resistance? a. Superconductors b. Semiconductors c. Metals d. Insulators 15. The Coulomb force (also called the electrostatic force) depends on the a. b. c. d. magnitude of electric charges separation distance between electric charges both of these none of these 16. The energy per Coulomb of charge supplied by a battery is its a. electric field b. voltage c. current d. resistance 17. As more lamps are put into a series circuit, the overall current in the power source a. b. c. d. remains the same decreases increases all of the above are possible 18. An electric current is formed by, a. b. c. d. Flow of neutral atoms. Flow of negative charges only. Flow of positive charges only. Flow of positive or negative charges. 19. In a circuit, a 4 Coulomb charge goes through a potential difference of 16 Volts. How much energy did the charge lose during this process? a. 4 J b. 16 J c. 0.25 J d. 64 J 20. The element of an electric oven is designed to produce 2000 Watts of heat when connected to a 110-Volt source. Calculate the resistance of the heating element. You may assume that this element is 100% efficient, that is, it converts all of the electrical energy into heat. a. 6 ohms b. 0.06 ohms c. 18.2 ohms d. 0.17 ohms 21. Calculate the cost of operating a 750-Watt appliance for 48 hours. The cost of energy is 10 cents per kilowatt-hour. a. $36.00 b. $3.60 c. $15.63 d. $1.56 22. A 3-Coulomb charge jumps from 68 Volts to 50 Volts. In this process the charge a. b. c. d. gains 18 Joules of energy loses 54 Joules of energy loses 18 Joules of energy loses 6 Joules of energy 23.A charge moving through a magnetic field experiences a force that is always a. b. c. d. in the same direction as the field perpendicular to the direction of the field opposite to the direction of the field none of the above 24.Two light bulbs are connected in series. What happens to the brightness of the other bulb if you short-circuit one of them? a.It gets dimmer b. It gets brighter c. It turns off completely d. There is no change in brightness 25. A typical 12 V battery has a rating of 60Ah. How much charge in Coulombs is in 60Ah? a. 3600 C b. 216,000 C c. 36 C d. 720 C