A moving coil galvanometer has a resistance of 60 $$\Omega$$ and it indicates full deflection on passing a current of 4.5 mA. A voltmeter is made using this galvanometer and a 4.5 k$$\Omega$$ resistance. The maximum voltage, that can be measured using this voltmeter, will be close to

A potentiometer wire, 10 m long, has a resistance of 40$$\Omega$$. It is connected in series with a resistance box and a 4 V storage cell. If the potential gradient along the wire is 0.4 mV cm^$$-$$1, the resistance unplugged in the box is