Which of the following pairs of instruments are null instruments? A. Ammeter and voltmeter B. The charge selector and triple beam balance C. Potentiometer and centre - zero galvanometer D. The Wheatst

1. Which of the following pairs of instruments are null instruments?
A. Ammeter and voltmeter
B. The charge selector and triple beam balance
C. Potentiometer and centre - zero galvanometer
D. The Wheatstone bridge circuit and the spring balance

A null instrument measures a quantity by balancing it against a known quantity, indicating a zero (null) deflection when balanced. A potentiometer measures potential difference by balancing it against a known potential difference, using a centre-zero galvanometer to detect the null point (zero current). This pair works together as a null measurement system. While a Wheatstone bridge is also a null instrument, a spring balance is a direct-reading instrument, not a null instrument.

The correct option is C.

2. A lethal dose of plutonium