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Name _________________________________________ Texas High School

Subject___________________, Period ____ Teacher _____________________ Date ____________

Lab Worksheet: Ohmmmmm, Ohmmmmm

Observations:

Table 1: Lamps In Series and Parallel

| Circuit | Dim or Bright |Did lamp light when one bulb was loosened? |

|One lamp | |XXXXXXXXXXXXXXXXX |

|Two lamps in series | | |

|Two lamps in parallel | | |

Table 2: Batteries In Series and Parallel

| Circuit | Dim or Bright |Did lamp light with one battery disconnected? |

|One battery | |XXXXXXXXXXXXXXXXX |

|Two batteries in series | | |

|Two batteries in parallel | | |

Table 3: Ohm’s Law

|Potential Difference (experimental|Current (amperes) |Resistance (ohms) |Potential Difference (calculated –|

|- volts) | | |volts) |

| | | | |

| | | | |

| | | | |

| | | | |

CONCLUSIONS/RELATED QUESTIONS (2 points each)

1. Compare the light given off by two lamps connected in parallel to the light produced when they are connected in series.

2. Why is the amount of light different when the lamps are connected in parallel?

3. What happened when you loosened one bulb in the series circuit?

4. Explain why this happened.

5. What happened when you loosened one bulb in the parallel circuit?

6. Explain why this happened.

7. A 9-volt battery (such as those used in radios) consists simply of six 1.5-volt batteries connected together. Are they connected in series or parallel? (Hint: check which battery setup on the front gave more power.)

8. List one advantage of connecting batteries in series.

9. List one advantage of connecting batteries in parallel.

10. List one advantage of connecting bulbs in parallel.

11. What is the difference between an open and a closed electric circuit?

12. Why should you leave the switch open while all connections in a circuit are being made?

13. In a ____________________ circuit, current must travel through all resistors.

14. Why are all appliances connected in parallel circuits in the home?

15. Some Christmas lights are wired in a ________________________ circuit. If one bulb burns out, all bulbs turn off.

16. From Table 3, what happens to the current as the resistance is increased?

17. What happens to the potential difference when the resistance is increased?

18. What happens to the current as the potential difference is increased?

19. What happens to the resistance as the potential difference is increased?

20. How do you account for the difference in the experimental and the calculated potential difference?

21. The relationship between current, potential difference, and resistance is called Ohm’s Law. It may be written as:

Current = potential difference/resistance

Current may be abbreviated as I, potential difference V, and resistance R. Substituting these symbols in

the formula above gives I = V/R

Now place the symbols I, V, and R correctly in the triangle below and use this triangle to solve the

following problems.

22. Find the current when a 12 volt battery is connected through a resistance of 50 ohms.

23. Calculate the potential difference in a circuit if the resistance is 200 ohms and the current is 10 amperes.

24. If the current is 10 amperes and the voltage is 120 volts, what is the resistance?

25. What is the voltage if the current is 35 amperes and the resistance is 20 ohms?

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