quinta-feira, 7 de junho de 2012

What: Questions of Electricity

  1. How many electrons are flowing every second through a light bulb if a steady current of 0.5 A passes through it.
  2. A uniform current of 1.0 A passes through a section of a wire. (a) What is the magnitude of charge passing through the wire in 10 seconds? (b) What is the number of electrons passing through the wire in 10 seconds?
  3. A steady current of 0.25 A passes through a cylindrical wire of radius 0.01 m. The current is uniformly distributed over the area of cross section. How many electrons per unit area are passing through the wire in 10 seconds?
  4. An electron gun in a TV set bombards the screen with a current of 5x10-6 A. (a) How many electrons strike the the TV screen every second? (b) How much charge falls on the TV screen in 30 seconds?
  5. Find the potential difference between the two ends of a wire of resistance 15 Ohm if 5.0 C of charges move through it in 10 seconds.
  6. An electric company runs two 5000m long wires from the main point to a small factory for an estimated load current of 100A. Calculate the drop in the voltage suffered at the factory if the wire resistance is 0.0005 Ohm per 100 m.
  7. An electric motor uses 3.0 A current when connected to a 115 V source. What is the power input of the motor?
  8. An electric light bulb is rated 100 Watts. How much current will it use if connected to a 110 V source?
  9. A 75 W bulb connected to a 115 V source outlet runs for 10 hours. (a) What is the work done by it? (b) What is the amount of charge passing through the bulb in 10 hours?
  10. An electric heater of resistance 50 Ohm uses 5.0 A of current when operates under steady condition. Compute its power if all the heat generated is due to the resistance.
  11. A refrigerator uses 1.5 A of current at 115 V. How much of energy will it use in 30 days?
  12. A television set uses 0.5 A when connected to a 110 V source. How much power will it consume if turned on?
  13. A 110 V source supplies 0.5 A of current to a toaster. (a) What is its resistance? (b) How much power does it use? (c) What would be the cost of running it for 15 minutes every day for 30 days. Cost of 1 KWH is $0.15.
  14. What is the potential drop across a 25 Ohm resistor if the current through it is 0.75A?
  15. The resistance of a cylindrical wire is 25.0 Ohm. What will be the resistance of the wire of same material if the length is doubled but the diameter is kept constant.
  16. The resistance of a certain wire is 10.0 Ohm. Find the resistance of the wire made out of same material if its diameter is doubled and the length is kept constant.
  17. The length and diameter of a cylindrical wire is doubled. What would be the ratio of new and original resistance?
  18. The resistivity of carbon is 3.5x10-5 Ohm.m. What should be the length of the carbon wire of 0.005 m in diameter if its total resistance is 3.5 Ohm?
Fonte: http://ensino.univates.br/~husemann/Eng/Circuitos_I/SUNY.pdf

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