Which of the two, namely voltmeter and potentiometer is preferable to measure the emf of a battery? Why?

Explanation

To determine which instrument is preferable for measuring the electromotive force (emf) of a battery, we will compare the voltmeter and the potentiometer based on their principles of operation, precision, and reliability.

### Step-by-Step Solution:

1. **Understanding the Instruments**:
- A **voltmeter** is an instrument used to measure the voltage (or emf) across two points in a circuit. It operates on the principle of a moving coil, which deflects in response to the current flowing through it.
- A **potentiometer** is a device that measures the voltage by comparing it to a known reference voltage. It works on the principle of a null point, where no current flows through the galvanometer connected to it when the potential difference is balanced.

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