204 



ELEMENTS OF GENERAL SCIENCE 



217. Series and parallel connections. The advantages and 

 disadvantages of series and parallel connections can be shown 

 with the apparatus in figure 100. In order to measure these 

 effects we must use the two instruments shown upon the 

 mounting board. That on the left is called an ammeter, that 

 on the right a voltmeter. The ammeter is connected in series 

 in the main circuit to be studied. The voltmeter is arranged 

 in parallel (shown by smaller wires) across the same circuit. 

 An ammeter is always connected in series, while a voltmeter 

 is placed in parallel with the circuit. 



The tungsten sign lamps can be used with ordinary dry- 

 cells and will enable us to perform several experiments. 

 The dry cells and lamps can be connected as suggested in 

 the table below. When the switch is closed, the pointer 

 on the ammeter scale moves a certain distance and the indi- 

 cator on the voltmeter scale does the same. The ammeter 

 pointer on an automobile is often noted to behave in the 

 same manner. The number of amperes designates the amount 

 of current in a circuit ; the volts refer to the electrical pressure 

 causing the electricity to flow. The values for the amperes 

 (ammeter reading) and the volts (voltmeter reading) for 

 various combinations are given in the following table: 



In the table above we learn from part A that three dry 

 cells arranged in series give a higher voltage than two cells 

 and send more current through the circuit. Part B shows that 



