Exam Question

### (a) Voltmeter
#### 1. Principle of Operation
A voltmeter is an instrument designed to measure the electrical potential difference, or voltage, between two points in a circuit. Its operation is based on Ohm's Law ($$ V = I \times R $$). A voltmeter is essentially a galvanometer (an instrument for detecting small electric currents) connected in series with a very high resistance, known as a multiplier.
- **Mechanism**: When connected across a component, a very small current flows from the circuit through the voltmeter's multiplier resistor and its internal coil. This current generates a magnetic field that interacts with a permanent magnet's field, producing a deflecting torque. The torque causes a pointer to move across a scale calibrated in Volts. The deflection of the pointer is directly proportional to the current, which is in turn proportional to the voltage being measured.