2. The picture to the right shows the galvanometer we will use in this week\'s l

Question

2. The picture to the right shows the galvanometer we will use in this week's lab. A galvanometer is an instrument which can detect very small currents flowing in an electric circuit. If there is a current flowing through the wires connected to the top of the galvanometer, the needle on the front will be deflected and the amount of current can be read from the scale. a) (2 points) If the galvanometer is connected as shown it measures a current of 25 mA. What would you expect the galvanometer to read if the two wires connected to the top were reversed? How does the person making the measurement detect this difference? PALMER FRES Note: This instrument is extremely sensitive and will be damaged by large currents, a:s such it should never be connected to the power supply! b) (2 points) How could you use a galvanometer to discriminate between a constant current and a pulse of current?

Explanation / Answer

a) It will again read 25 mA, but this time the needle direction would get reversed. Say, earlier it was deflecting towards right, now it will get deflected towards left. The person detects it by noting that the current direction has changed.

b) In case of constant current, galvanometer needle would stay at a single position for large time. Whereas in case of a pulse of current, the needle would get deflect for a very short period of time and again it will come to the zero mark.

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