<p>Box A, in the set up shown in Fig. 7.69, represents an electric device often used/needed to supply, electricity power from the (ac) mains, to a load. It is known that&nbsp;<span class="equation">\(V_{o} &lt; V_{i}\)</span></p>

<p><img alt="" src="https://school.achievam.com/upload/questionbank/question/que_1759026852.PNG" style="height:120px; width:320px" /></p>

<p>(a) Identify the device A and draw its symbol.</p>

<p>(b) Draw a schematic diagram of this electric device. Explain its principle and working. Obtain an expression for the ratio between its output and input voltages.</p>

<p>(c) Find the relation between the input and output currents of this device assuming it to be ideal.</p>