Lab Report Galvanometer as a milliammeter the simplest circuit: the one in Figur

Question

Lab Report Galvanometer as a milliammeter the simplest circuit: the one in Figure 1. Set it up and have it checked by instructor before closing it. Use a single 1.5V battery. As the maximum allowed current for the galvanometer is 1.0 mA, set the resistance at at least 1.5 k2 b) Change R so that the current I changes in steps of O.ImA and fill the table below R () I (A) RxI (units- ) .34 Why is the product RxI (almost) constant? c) Plot R (vertical axis) versus 1/1 (horizontal axis) and find slope and intercept What is the meaning of the slope? What is the meaning of the intercept? (hint: what elements of the circuit have in resistances?) ternal

Explanation / Answer

Conversion of galvanometer into milliammeter

Milliammeter is an instrument that is used to measure the current in the circuit therefore it has to be connected in series with the circuit. Therefore the resistance of this instrument must be very low (ideally zero) so that the current in the circuit is not altered and the reading is error less. To decrease the resistance of the instrument the galvanometer of some finite resistance is connected a shunt resistance of very small magnitude in parallel to the galvanometer resistance.

Conversion of galvanometer into voltmeter

Voltmeter is used to measure the voltage difference between two points in the circuit. Therefore the resistance of voltmeter must be such that the current through the resistance whose voltage difference needs to be measured is not altered. In order to do that the resistance of the instrument must be very high (ideally infinite) so that no current or negligible current passes through it and only voltage difference is measured.

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