Physics Worksheet Electric Current Section: Name:

Transcription

1 Do Now: Water Flow vs. Electric Current Models: f an electric circuit consists of wires, a battery and a light bulb, please compare the water flow in the following picture to the electric current in a circuit: 3. Draw a simple electric circuit using symbols of wires, a battery, and a light bulb. Then, overlay the three basic physics quantities on the circuit. Measuring oltage & Current 4. We can measure the oltage using, and its symbol is: 5. We can measure the Current using, and its symbol is: Pump: Water pipe: Water Mill: Height: High PE Water: 6. We can measure the oltage, Current and esistance using: 7. Draw a simple electric circuit using symbols. Then, add the symbol of instruments in order to measure the voltage and current of the circuit. Low PE Water: Flow of Charge and Electric Circuits 1. Draw a simple electric circuit using wires, a battery, and a light bulb, and draw the same circuit next to it using symbols of them. 8. What is the Ohm s Law: Ohm s Law 2. List the three basic physics quantities in an electric circuit, including their names, symbols, units, and symbols of units. Physical Quantity Symbol Unit Symbol of Unit Graph: elation: Mr. Lin 1

2 14. A 2.5-MΩ resistor has a 0.02-mA current in it. What is the voltage across the resistor? elation: 15. A simple circuit uses a 9.0- battery and uses 20KΩ resistor, what s the current of the circuit? elation: 9. What is the current through a 4-ohm resistor connected to a 12- power supply? 16. A circuit uses a car battery and draws 0.5 A of current, what s the resistance of the circuit? 10. A 5-ohm resistor has a 8-A current in it. What is the voltage across the resistor? 17. Find the current of the following electric circuit? 20Ω 11. What is the resistance of a device that uses 2.5 A of current when connected to a 15-volt power source? Find the resistance of the following electric circuit? 12. What is the current through a 6-KΩ resistor connected to a 9- power supply? 0.2 A Find the voltage of the following electric circuit? 13. What is the resistance of a device that uses 0.5 ma of current when connected to a 5-volt power source? 0.4 A 8KΩ Mr. Lin 2

3 27. How much current must there be in a circuit if 100 esistors coulombs flow past a point in the circuit in 4 seconds? 20. A resistor is 21. esistors are used to control, since in an electric circuit,. Units of resistors are. 22. What are the factors to determine the resistance? 28. f there is a current of 20 amperes in a circuit for 10 minutes, what quantity of electric charge flows in through the circuit? Factor Symbol Unit 29. How much time is required for 10 coulombs of charge to flow past a point if the rate of flow (current) is 2 amperes? Formula of resistance: 23. A 0.5-m long Nichrome wire has m 2 cross-section. What is the resistance of the wire? oltage Sources 30. A voltage source is: 24. A 1.2 x 10 5 Ω Copper wire has m 2 cross-section. What is the length of the wire? 31. oltage sources:. Electric Current 25. Electric current is. 1) n solid conductors:. 2) n fluids:. 26. Direction of current: 1) Electric (conventional) current:. Units of oltages are:. 32. The potential energy per coulomb of charge ( = W / q ) available to electrons moving between terminals is the (is also called the or emf). 33. Examples of voltage source: 2) Electron flow:. Formula:. Units of electric current. Mr. Lin 3

4 Batteries in Parallel and in Series 34. Compare the following three cases: or t n North America AC is, Hz. 38. AC to DC Conversion: (A) Single:. (B) Parallel:. (C) Series:. 35. Calculate the current in the following three cases: Steps of conversion: (A). (B). (C). (D). (A) (B) (C) DC and AC (Direct Current and Alternate Current) 36. What is DC: Speed of Electrons 39. What is thermal speed of electrons? The speed is about:. 40. What is drift speed of electrons? The speed is about:. or t 41. Why does the electric power company charge you money when they provide you AC electricity which no net electrons enter your home? 37. What is AC: Where is the source of electrons in the AC outlet? Mr. Lin 4

5 Electric Power 45. A light bulb is plugged into a 120-volt outlet and has a 42. Definition of Electric Power: 0.7 A current in it. What is the power rating of the light bulb? Formula: Unit of electric power: ewrite the electric power formula in terms of and. ewrite the electric power formula in terms of and. 46. A heater uses 21 A when connected to a 110- line. f electric power costs 10 cents per kilowatt-hour in this location, what is the cost of running the heater for 13 hours? ewrite the electric power formula in terms of and. Electric Power Formulas: Electric Energy 43. Formula in terms of P and t. 47. A 120 outlet in Tony s house is wired with a circuit breaker on an 8 A line. a) f Tony tries use his newlybought 1200-Watt hair dryer, will he trip the circuit breaker? b) What is the resistance of the hair dryer? Unit of electric energy: ewrite the electric power formula in terms of, and t. ewrite the electric power formula in terms of, and t. ewrite the electric power formula in terms of, and t. 48. Alice likes to keep her 40-Watt front porch light on at night time from 10 p.m. to 6 a.m., and Alice pays 8.00 per kwh, how much does it cost to run the light for this amount of time each week? Electric Energy Formulas: Kilowatt-Hours (kw h) 44. Calculate 1 kw h = J. Mr. Lin 5