Pre-LAB 4 Assignment Fundamentals of Circuits II: Currents ...

Fundamentals of Circuits II: Currents & Circuits v 0.3
Prediction 3.2 Predict how the current through bulb B will change, if at all, when circuit
10(a) is changed to 10(b) (when bulb C is added in parallel to bulb B). What will happen to the
brightness of bulb B? Explain the reasons for your predictions.
Prediction 3.3 Also predict the relative rankings of brightness for all the bulbs, A, B, and C,
after bulb C is in the circuit. Explain the reasons for your predictions.
Activity 3.1: A More Complex Circuit
Step 1: Set up the circuit shown in Fig. 11(a). Convince yourself that this circuit is identical
to Fig. 10(a) when the switch, S, is open, and to Fig. 10(b) when the switch is closed.
+ −
CP1
A
A
+
−
S
+
−
+
CP2
−
S
B
C
B
C
(a)
(a)
Figure 11: (a) Circuit equivalent to Fig. 10(a) when the switch, S, is open and to Fig. 10(b)
when the switch is closed. (b) The same circuit with current probes connected to measure the
current through bulb A (CP1) and the current through bulb B (CP2).
Step 2: Observe the brightness of bulbs A and B when the switch is open, and then the
brightness of the three bulbs when the switch is closed. Compare the brightness of bulb
A with the switch open and closed, and rank the brightness of bulbs A, B, and C with
the switch closed.
Question 3.5: If you did not observe what you predicted about the brightness, what
changes do you need to make in your original reasoning? Explain.
Step 3: Connect the two current probes as shown in Fig. 11(b). Use same the experiment file
L2A1-2 (Two Currents) that you have used in the previous activities.
PHYS-204:Physics II Laboratory 18