The circuit shown in Figure 31.44 includes a variable resistor, the resistance \(R_{\text {var }}\) of which can be adjusted, and a resistor of unknown value \(R\). A circuit with such a network of resistors is called a Wheatstone bridge and can be used to determine the value of the unknown resistance \(R\) by adjusting the variable resistor so that the light bulb does not glow. The light bulb is initially glowing when \(R_{\text {var }}\) is set to \(20 \Omega\), but it goes out when \(R_{v a r}\) is adjusted to \(12 \Omega\). Determine the current in the battery when the light bulb is out.

Data from Figure 31.44

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