4. The circuit shown is called the Wheatstone bridge. It is used to find the value of an unknown resistor R4 by comparison with the 3 known resistors R1, R2, and R, that can be varied. These resistors are varied until the current in the galvanometer G is 0; the bridge is then balanced and the voltage between points C and D is 0; then 13-11 and 14-12. (a) In terms of voltage V and resistors, find 12. (b) Find the relation between the four resistors. (c) Find the equivalent resistance R of the circuit. R₂ R₂

4. The circuit shown is called the Wheatstone bridge. It is used to find the value of an unknown resistor R4 by comparison with the 3 known resistors R1, R2, and R, that can be varied. These resistors are varied until the current in the galvanometer G is 0; the bridge is then balanced and the voltage between points C and D is 0; then 13-11 and 14-12. (a) In terms of voltage V and resistors, find 12. (b) Find the relation between the four resistors. (c) Find the equivalent resistance R of the circuit. R₂ R₂