When the length of a wire is doubled, the ammeter reading reduces to _____.

1. Resistance is directly proportional to length, so doubling length doubles resistance. 2. By Ohm's law I = V/R, doubling R at constant V halves the current. 3. Hence the ammeter reading reduces to half. _Source: RRB Group D CEN-02/2018 PYQ, Q.54._