Explanation:

- Voltmeter (Option 1):

- This is the correct option.

- A voltmeter measures the electrical potential difference between two points in an electric circuit.

- It is connected in parallel with the circuit components.

- Galvanometer (Option 2):

- It measures small electric currents.

- It can be used to detect the presence of current in a circuit.

- Ammeter (Option 3):

- It measures the current flowing through a circuit.

- It is connected in series with the circuit.

- Bolometer (Option 4):

- It measures electromagnetic radiation power.

- Used in fields like astronomy for measuring heat from stars.