Charley’s Thinking on the Thevenin Equivalent Circuit As discussed in, there is generally a need for an adjustable and readable voltage source (with a voltmeter) and an ammeter to find the Thevenin equivalent of a network, especially if it contains a dependent source. If the network has an independent source, only a voltmeter and an ammeter are needed since the Thevenin voltage source is just the open-circuit voltage V_Th = V_oc and the Thevenin equivalent impedance can be obtained from dividing the open-circuit voltage by the short-circuit current as Z_Th = V_oc/I_sc However, Charley, who had previously burnt out an ammeter when measuring a large current over its rated current and received a warning from the lab T.A. that he would fail the lab course with another mistake, is worried that short circuiting the terminals of the network results in a large current exceeding the rated current of the ammeter, which may cause the ammeter to be damaged. Therefore, instead of using an ammeter, he connected a 20Ω resistor across the terminals and measured the terminal voltage V_ab = 2 V after measuring the open-circuit voltage V_oc = 5 V (see Figure P2.11). Find the equivalent resistance of the network based on his data, unless you disagree with him.