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Wheatstone bridge: concept and application


Consider the following circuit of three known resistors, R, start subscript, 1, end subscript, R, start subscript, 3, end subscript, and R, start subscript, 4, end subscript, an unknown resistor R, start subscript, 2, end subscript, and a galvanometer connected between the points start text, B, end text and start text, C, end text.
The circuit is connected to a cell of unknown voltage.
If the current in the galvanometer, I, start subscript, start text, G, end text, end subscript, equals, 0, what is the resistance, R, start subscript, 2, end subscript?
R, start subscript, 2, end subscript, equals
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text