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Name _________________________________________
Subject___________________, Period ____ Teacher _____________________
Texas High School
Date ____________
Lab Worksheet: Ohmmmmm, Ohmmmmm
Observations:
Table 1: Lamps In Series and Parallel
Dim or Bright
Did lamp light when one bulb
was loosened?
Circuit
One lamp
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Two lamps in series
Two lamps in parallel
Table 2: Batteries In Series and Parallel
Dim or Bright
Did lamp light with one
battery disconnected?
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Circuit
One battery
Two batteries in series
Two batteries in parallel
Potential Difference
(experimental - volts)
Table 3: Ohm’s Law
Current (amperes)
Resistance (ohms)
Potential Difference
(calculated – 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?