LABORATORY OBJECTIVES 1. To determine the characteristics of an analog galvanome
ID: 1881437 • Letter: L
Question
LABORATORY OBJECTIVES 1. To determine the characteristics of an analog galvanometer 2. To use the galvanometer as a voltmeter 7-2 To use the galvanometer as an ammeter INTRODUCTION An analog galvanometer consists magnetic field. When a microampere current flows through the coil, a pointer attached to the coil rotates through an angle proportional to the current. The internal resistance of the galvanometer coil is denoted by r, and the current necessary for a full-scale de- flection of the galvanometer is denoted by ig Ig and r are called the galvanometer mounted so it can rotate in a characteristics. FIGURE 7-1. A galvanometer A voltmeter is a galvanometer used to measure potential difference between two points, and must therefore be placed across (ie., in parallel with) a part of the circuit. Since the voltmeter itself must not become part of the circuit, an ideal voltmeter consists of a galvanometer in series with a large resistance M called the multiplier. If a full- scale deflection occurs for a potential of V volts, then Ohm's law requires Power supply Voltmeter FIGURE 7-2. A voltmeter made of a galvanometer and a series multiplier resistor M, set on the decade resistor, is shown connected to the power supplyExplanation / Answer
Some key points
• A galvanometer is converted into voltmeter by connecting a very high resistance in series with the galvanometer.
• To convert galvanometer into ammeter a very low resistance known as shunt is connected parallel to the galvanometer.
(1) the range of voltmeter from 200 V to 20 V is done by decreasing the series resistance by factor 10. (So changing factories 10 and it is decreasing )
(2) when we press DCA button then the metre changes the series resistance to parallel resistance in in order to measure DC current.
(3) the range of ammeter from 20 mA to 200 mA can be done by decreasing shunt resistance by factor one-tenth.
(4) it happens because the shunt resistance is decreased when the the meter is switched from the 300mA range to 3 A range therefore more current is allowed to flow through the shunt resistance, and that is why light bulb glows brighter.
(4) Yes, our meter reading agrees with standard meter. (Percentage difference can be calculated by experiment observation reading. By the way generally it is at most 5 %)
(5) probable source of error can be occur due parallax error, or due to any human errors.
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