(a) The potential difference between two points is said to be 1 volt when 1 joule of work is done in moving a charge of 1 coulomb from one point to the other.
$$V = \frac{W}{Q}, \quad 1 \text{ V} = \frac{1 \text{ J}}{1 \text{ C}}$$
(b)
(i) The symbol (circle with letter A) represents an Ammeter.
Function: It measures the electric current flowing in a circuit. It is always connected in series.
(ii) The symbol (zigzag with an arrow) represents a Variable Resistor (Rheostat).
Function: It is used to vary or regulate the current in a circuit by changing its resistance.
Source: Chapter 11 – Electricity, Sections 11.1 and 11.2
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