Correct Option
The correct option is 2, 3 and 4 only
Explanation
Electrical devices and measuring instruments are connected in specific configurations (series or parallel) within a circuit. This placement depends on whether the device is intended to measure flow (current), measure potential difference (voltage), or control/protect the circuit, as well as the device's internal resistance.
Statement-wise Analysis
- Pair 1 is Incorrect: An Ammeter is used to measure the electric current flowing through a circuit. Since current remains constant in a series combination, an ammeter must be connected in series with the circuit component to measure the full current passing through it. It has very low resistance to minimize voltage drop.
- Pair 2 is Correct: A Voltmeter measures the potential difference between two points. To measure the voltage drop across a component, it is connected in parallel to that component. It has very high resistance to draw negligible current from the circuit.
- Pair 3 is Correct: A Fuse is a safety device that protects electrical appliances from excessive current. It is connected in series (typically with the live wire) so that if the current exceeds the rated value, the fuse melts and breaks the entire circuit, stopping the flow of electricity.
- Pair 4 is Correct: A Rheostat is a variable resistor used to control the magnitude of current flowing in a circuit. To regulate the current reaching a component, the rheostat is typically connected in series with that component.
Key Takeaway
Ammeters, Fuses, and Rheostats (for current control) are connected in series, while Voltmeters are always connected in parallel to the component being measured.