Question: How are current and voltage measured in a circuit? Part P-1: The Ammet

Question

Question: How are current and voltage measured in a circuit? Part P-1: The Ammeter To measure the current flowing through a device, an ammeter An ammeter is a must be connected in series with the device. That means the device for measuring current must flow through the meter before or after it flows the flow of current in through the device you are attempting to measure. Figure 1 electric circuits. shows two ways of connecting an ammeter to measure the current through a resistor Figure 1 The ammeter in Figure 2 will not read the current through the device, because a large current wi flow around the device and through the ammeter, very little will flow through the device. Connecting an ammeter in this fashion is also likely to burn out the ammeter. When using an ammeter properly, you will alway be disconnecting a wire at the point you want to measure the current and inserting the ammeter in the circuit at that point. For example, figure 3 sho how to measure the current through resistors A au B, by disconnecting the wire from A to B and inserting the ammeter into the circuit. 1. Why would you not want to place the ammeter in the way shown in figure 2? W would it destroy the ammeter? Figure 2: Never connect the ammeter in this way. It will likely destroy the ammeter. Constructing Basic Circuits -6.1 Last Revised 12/21/2015

Explanation / Answer

1). Ammeter has low resistance so that it can measure current flowing through the circuit correctly. But when it is connected in parallel to load then current will follow the low resistance path and thus will flow through the ammeter thereby damaging the circuit.

2). Ammeter is always connected in series since current in series remains same. Thus to measure the current flowing through A and B, we can connect ammeter is series with the resistances A and B in the wire inbetween the junctions.

3). We know that ammeter has low resistance since it is connected in Series to measure current while Voltmeter has high resistance since it is connected in parallel to measure the voltage. Now if we connect the multimeter in Series to measure the current and select the wrong setting, i.e. set the multimeter as voltmeter then due to the high resistance value of voltmeter being added in Series, no current will flow through the circuit.Similarly if we connect the multimeter in parallel to the load to measure the voltage but set it by mistake as ammeter then current will follow the low resistance path and will flow through it and damaged the circuitary.

Hence its very important to set the settings properly.

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