Question

Which Instrument measures electric current?

• A. Voltmeter
  (B) Ammeter
• B. Barometer
• C. Thermometer

Hint:

Use the unit names to remember the tools: Ampere $\rightarrow$ Ammeter. Volt $\rightarrow$ Voltmeter. This "unit-to-tool" connection makes it easy to remember.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the name of the specific device used to measure the flow of electric current within an electrical circuit.
Step 2: Detailed Explanation:

• Function of an Ammeter: An ammeter is an instrument designed to measure electric current. Its name is derived from the unit of current, the Ampere (A).
  
• Circuit Connection: To get an accurate reading, an ammeter must be connected in "series" with the part of the circuit through which the current is being measured. This ensures that all the charge flowing through that component also flows through the meter.
  
• Internal Resistance: An ideal ammeter is designed to have zero internal resistance. This is crucial so that its presence in the circuit does not impede the flow of current and alter the measurement.
  
• Analyzing Other Instruments:
  - Voltmeter (A): This device measures the voltage (electrical potential difference) between two points and is always connected in parallel.
  - Barometer (C): This is a meteorological instrument used for measuring atmospheric pressure.
  - Thermometer (D): This instrument is used for measuring temperature.
  
• Safety Warning: Due to its very low resistance, connecting an ammeter in parallel across a voltage source will create a short circuit, which can damage the meter, the circuit, and the power supply.
  

Step 3: Final Answer:
The ammeter is the correct instrument specifically designed for measuring electric current.