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Name ____________KEY___________________________ Period _________ Date ____________ Unit 11 – Electricity Review 1. Why does the heating element in a toaster or a filament in a light bulb get hot and glow? Because of friction due to the element / filament being a poor conductor. 2. Describe the Earth’s magnetic field vs a compass. The Earth’s geographic north pole is actually a magnetic south pole since a compass’ north-pointing pole is attracted to the geographic north pole. 3. What mechanism uses mechanical energy to produce electrical energy? Electrical generator 4. What device converts electrical energy to mechanical energy? Electrical motor 5. The higher the amount of current flow through a material, the ____________ the conductivity. Better 6. In a parallel circuit, what is the current through a 6 ohm resistor when the circuit is connected to a 12 V battery? I = V/R I= 12/6 I= 2 A 7. What is the current flow in a circuit with 10 V battery and a 12.2 ohm resistor? I=V/R I=10/12.2 I= 0.819672131 ROUND I=0.82 A 8. An open circuit ________________ electricity to flow? Does not 9. Why are the light bulbs in a series circuit progressively dimmer? The more light bulbs in a series circuit, the more resistance they create. This makes 3 light bulbs dimmer than 1. 10. Why do batteries have a longer life in a series circuit rather than a parallel circuit? Bulbs in series draw less current from a battery than bulbs in a parallel circuit. 11. If a material, such as glass or plastic, is inserted into a circuit and it does NOT let the light bulb light up, then it is a _____________________. Insulator 12. What is the resistance when a 12 v battery sends a 0.25 amp current through a light bulb? R=V/I R= 12/0.25 R = 48 ohms 13. A radio has a resistance of 7.25 ohms, and 120 volts is supplied. What is the amount of current flowing? I=V/R I=120/7.25 I = 16.55 amps 14. How does an electromagnet used in a junk yard pick up a car and then later drop it where they want it? To activate the magnet, current is turned on. To turn off the magnet, current is turned off. 15. Light bulbs will glow _____________ when a good conductor is used. Brightest 16. Is the school lights wired in series or parallel? Why? Parallel, so one light at a time can be turned on or off.
