Physics 271L Exp 8: Exercise 3

3. Construct the circuit in Fig. 3. Set the current = 1 amp.

Exp8Fig3.gif (4430 bytes)

(a) If the tap switch is suddenly closed, what is the direction of the induced current in the galvanometer? Note magnitude and direction of deflection.
What deflection direction does Lenz' Law predict for the induced current in the many-turn coil?

Does the deflection of the galvanometer confirm this?

If you keep the tap switch closed, what will be the galvanometer deflection? ______

Why? _____

When you release the tap switch, what is the corresponding galvanometer deflection ?

(compare magnitude and directions now to when the switch was closed).

(b) Move the coils farther apart, but still coaxial. How does the magnitude of the deflections compare (to when the coils were closer) on opening and closing the tap switch?
Increase the steady state current in the few-turn coil. How does the magnitude of the deflection change (as compared to the lower current) on close and opening the tap switch?
(c) Interchange the Many-turn and Few-turn coils (terminals A to A and B to B). Keep the coils in the same relative position as in part 3 (a), and make the current in the "primary" at 1 amp.
When the switch is closed, is the resulting deflection greater than, equal to, or less than the deflection of 3 (a)? Explain.
(d) Now place the iron core in the center of the coils. Close the tap switch and observe the
magnitude of the deflection. Explain.

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