TP Physique2

Use of the Ammeter 

An ammeter must always be placed in series in an electrical circuit because of its small internal resistance. On an ammeter, we notice values mentioned having different units (A, mA…), these represent what we call a caliber.

Realize the electrical circuit of the figure 1, where R represents an electrical resistance and E being the symbol of the direct voltage generator which powers the electrical circuit. Set E to the value E=6V and using a needle ammeter (un amperemètre à aiguilles), measure the intensity of the electric current flowing in the circuit. Report the obtained value without forgetting the unit   I =………………………….

Use of the voltmeter

The voltmeter is an electrical device that allows you to measure the voltage at the terminals of an electrical device. It is designated in a circuit by the symbol :

A voltmeter must always be placed in parallel in an electrical circuit because of its high internal resistance.

Realize the electrical circuit of the figure 1, set the direct voltage generator to the value E=6V. Connect the voltmeter to the terminals of a resistance R (positive terminal with the input of R and negative terminal with its output) and measure the value of the voltage across the resistor R using a suitable caliber.

Report the obtained value without forgetting the unit         V=………………………….

Remark : The ammeter and the voltmeter are polarized devices, having two positive and negative terminals, their polarities must be respected before connecting them to the circuit. On the other hand, an electrical resistance is not polarized and has an input and an output.

A caliber : Represents the highest value that the device can measure, i.e., the maximum value reached during a measurement.

Use of the multimeter

The multimeter is a device with a digital display which can have several functions depending on the needs of the experimenter: It can be used as an ammeter, voltmeter or ohmmeter (measurement of the value of a resistance). The multimeter contains terminals (see figure 2), terminals D and C are chosen if you want to measure a voltage or resistance, terminals B and C in the case of measuring low currents while A and C for high currents. The COM terminal is equivalent to the negative pole of the multimeter.

Use of the oscilloscope :

An oscilloscope is a device used to analyze with great precision the behavior of a variable and repetitive electrical signal (potential). The oscilloscope screen is nothing more or less than a graph of potential versus time on which we can visualize the behavior of the potential during an entire cycle. The oscilloscope automatically identifies the repeating cycle and displays it motionlessly on the screen (see Oscilloscope Appendix).

1. Connect the oscilloscope, the generator and the voltmeter (see first figure of the PW5).
2. Complete the table below :
   

3. What is the absolute reading uncertainty committed to the measurement of V_max ?

• What is the voltage measured by the voltmeter ?
  

• Calculate:

• -- What does V_G represent ?