WAEC Physics 2019 Paper

Concept: A balanced meter bridge follows the Wheatstone bridge principle. For equal gap resistances, the null point divides the meter wire into equal lengths.Explanation: Let the unknown length from one end of the meter bridge be $x$. The two gap resistances are equal, each being $2\,\Omega$. Under balanced conditions, the bridge satisfies $\frac{2}{x} = \frac{2}{100-x}$. Cross multiplying gives $2(100-x) = 2x$. Simplify the equation: $200-2x=2x$. Combine like terms to get $200=4x$. Divide both sides by $4$: $x=\frac{200}{4}$. Therefore, $x=50\,\text{cm}$.Answer: $x = 50\,\text{cm}$