Passage IV

A transformer is an electrical component used to increase or decrease voltage. In 3 experiments, a group of students studied transformers using the setup shown in Figure 1.

An input coil was wrapped N_in turns around one side of a core (a solid ring) and then connected to an ammeter (current-measuring device) and a power source. An output coil was wrapped N_out turns around the opposite side of the core and then connected to an ammeter and a voltmeter. U_in and U_out were the input and output voltages (in volts, V), respectively. I_in and I_out were the input and output currents (in milliamperes, mA), respectively.

Experiment 1

In Trials 1-12, the core was made of iron, and the power source was a generator of alternating current (AC; current that varies over time). The students measured I_in, U_out, and I_out for various combinations of N_in, N_out, and U_in (see Table 1).

Experiment 2

In Trials 13-17, the procedure followed in Trial 5 was repeated except that the core material was varied (see Table 2).

Experiment 3

The procedures followed in Trials 1-12 were repeated, except that the power source was a battery supplying direct current (DC; current that remains constant over time). The I_in results matched those of Experiment 1, but in every trial, U_out was 0 V and I_out was 0 mA.