Ammeter Connection for Current Measurement

To accurately measure the current flowing through a circuit component like a bulb, an ammeter must be connected correctly. This ensures the ammeter functions properly and does not damage the circuit or itself.

Understanding Ammeter Usage

An ammeter is a device used to measure the electric current in a circuit. Key principles for its use include:

• Series Connection: An ammeter must always be connected in series with the component through which the current is to be measured. This allows the entire current to flow through the ammeter.
• Correct Polarity: The positive terminal of the ammeter should be connected towards the positive terminal of the power source, and the negative terminal towards the negative terminal. Connecting with reversed polarity can damage the ammeter.
• Circuit Completion: The circuit must be complete, including a power source (like a battery), for current to flow and be measured.

Evaluating the Options

• Option 1: Connect the ammeter without a battery - Incorrect. A battery is necessary to establish a current flow in the circuit, which the ammeter needs to measure.
• Option 2: Connect the ammeter with reversed polarity - Incorrect. Reversing the polarity can damage the ammeter and lead to incorrect readings.
• Option 3: Connect the ammeter in series with correct polarity - Correct. This is the standard and safe way to connect an ammeter to measure current through a component like a bulb.
• Option 4: Connect the ammeter in parallel with the bulb - Incorrect. Connecting an ammeter in parallel has a very low internal resistance, which would cause a short circuit, drawing excessive current and potentially damaging the ammeter, bulb, or power source. Voltmeters are connected in parallel.

Therefore, the essential precaution is to connect the ammeter in series with the correct polarity.