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Content Benchmark P.12.B.2 Students know magnetic forces and electric forces can be thought of as different aspects of electromagnetic force. I/S Sample Test Questions 1st Item Specification: Describe the relationship between electric currents and magnetic fields. Depth of Knowledge Level 1 1. The process by which an electric current is produced by moving a wire through a magnetic field is called A. the flow of electrons. B. electrical resistance. C. electromagnetic induction. D. electrical resonance. 2. A temporary magnet made by wrapping a current-carrying wire around an iron core is known as a/an A. alkaline battery. B. electromagnet. C. magnetic pole. D. magnetic compass. Depth of Knowledge Level 2 3. Which of the following are different aspects of the same force that allows generators and transformers to work? A. Magnetic forces and electric forces B. Magnetic forces and nuclear forces C. Electrical forces and mechanical forces D. Electrical forces and frictional forces 4. Study the diagram of electromagnetic induction below. (From www.physics.uiowa.edu/.../inductance.gif) Which of the following BEST describes the principle of electromagnetic induction? A. A magnetic field moving around a coil of wire causes an electric current, and an electric current in a coil of wire causes a magnetic field. B. The flow of electrons through either a series or parallel circuit is known as an electric current. C. Motors, telephones, and computers are all devices that contain electromagnets. D. When two charged objects are held close together they will either attract each other or repel each other through electromagnetic forces. 2nd Item Specification: Apply the concept of electromagnetic induction to explain the operation of generators and transformers. Depth of Knowledge Level 1 5. Electromagnetic induction is the process by which an electric current is produced by moving a wire in a magnetic field. Which of the following devices works on the principle of electromagnetic induction? A. Light bulb B. Compass C. Battery D. Generator 6. A transformer is a device in which alternating current in one coil of wire induces a current in a second coil. Which of the following properties is necessary for a transformer to work? A. Voltage is a measure of the amount of force pushing a current. B. A wire carrying an electric current induces a magnetic field around it. C. Electricity is transmitted over power lines at very high voltages. D. When electrons flow through a material they meet resistance. 7. A transformer is a device in which alternating current in one coil of wire induces a current in a second coil. Which of the following properties is necessary for a transformer to work? A. When a magnetic field changes an electric current will be induced. B. Magnets are needed for an electrical current to flow through wires. C. High voltage is needed to transfer electric current long distances. D. A higher voltage is needed to run large appliances than small ones. Depth of Knowledge Level 2 8. Which of the following are different aspects of the same force that allows generators and transformers to work? A. Electricity and magnetism B. Electricity and mechanics C. Conductors and nonconductors D. Electrical and nuclear power 9. Which of the following devices work because an electric current is induced when a wire moves across magnetic lines of force? A. Generator and transformer B. Generator and magnet C. Battery and transformer D. Battery and magnet 10. A device used to transform to raise or lower voltage is called a transformer. Observe the following diagram of a step-down transformer. (From www.explainthatstuff.com/transformer_stepdown.gif) In order for a transformer to cause a change in voltage the core must A. be able to be magnetized. B. be an electrical insulator. C. be made of wood or plastic. D. be attached to a battery. 11. Which of the following correctly describes a purpose of an electrical transformer? A. Increase the resistance to the electrical current. B. Increase the current carried by the power lines. C. Change the voltage carried by the power lines. D. Change the magnetism carried by power lines. 12. Observe the following model of an electrical generator. (From http://www.energyquest.ca.gov/story/chapter06.html) Which of the following explains why a generator can convert mechanical energy into electrical energy? A. Spinning a loop of wire between a metal and nonmetal produces an electric current in the metal. B. Spinning a loop of wire between a conductor and nonconductor produces an electric current. C. Spinning a loop of wire in the magnet’s magnetic field produces an electric current in the wire. D. Spinning a loop of wire in the magnet’s magnetic field produces an electric current in the magnet. Content Benchmark P.12.B.2 Students know magnetic forces and electric forces can be thought of as different aspects of electromagnetic force. I/S Answers to Sample Test Questions 1. C, DOK Level 1 2. B, DOK Level 1 3. A, DOK Level 1 4. A, DOK Level 2 5. D, DOK Level 2 6. B, DOK Level 1 7. A, DOK Level 1 8. A, DOK Level 1 9. A, DOK Level 2 10. A, DOK Level 2 11. C, DOK Level 2 12. C, DOK Level 2