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Lamp Circuits

1.      Connect one lamp and the battery pack so the lamp will glow.  How bright is it (dim, blinding, choose your adjective carefully)?

2.      Try the other lamp.  Does it glow as brightly as the other does?  What can you say about their resistances?

3.      The maximum specifications for the #222 light bulbs used in this exercise are:  2.25V, 0.25A.   What are the resistances of each lamp?  What is the maximum power each can dissipate before each burns out?  According to your answer, what should happen if you connect just one light bulb across the battery pack?

4.      Connect the two lamps in series.  Draw the circuit.    Explain what you observe in terms of the brightness of the lamps.

5.      Connect the two lamps in parallel.  Draw the circuit.  What do you observe? Explain what you observe.

6.      In the box you will find two resistors, one with a clear plastic covering and the other which is black.  Describe a way to tell the resistance of each relative to a lamp (bigger or smaller than a lamp).  Draw the necessary circuit(s).

7.      What is the relative resistance of the one with the clear plastic cover?

8.      What is the relative resistance of the one with the black cover?

9.  Make a light dimmer out of the variable resistor (“pot”), lamp and battery.  Draw the circuit.

10. We will now use the blue volt-ammeter in the box to calculate the resistance of the resistor with black and brown bands painted on it.   Connect the resistor to both terminals of the battery. Slide the bar on the volt-ammeter until the V is visible. Connect the central connector of the meter to one side of the resistor. The other side of the resistor should be connected to one of the connectors on the right hand side.  The number below the connector tells you the maximum voltage in volts that the meter can accurately read for that connector. If the meter needle goes off scale to the left, switch the leads. If the meter needle goes off scale to the right, go to a higher maximum voltage connector. Measure the voltage drop across the resistor.

11.Slide the bar so that the A is visible. Connect the battery, ammeter and resistor in series. If the meter needle goes off scale to the left, switch the leads.  If the meter needle goes off scale to the right, go to a higher maximum current connector.  Measure the current through the resistor.

12. Using the measured voltage drop across the resistor and the current through the resistor, calculate the resistance, in Ohms, of the banded resistor.