In an electric circuit, the device that acts as a variable resistor is called  __________.

Correct option is D

The correct answer is (d) Rheostat

Explanation:

• A rheostat is a device that acts as a variable resistor in an electric circuit. It allows the resistance to be adjusted manually, thereby controlling the current flowing through the circuit.
• This is useful for controlling the brightness of a light bulb, the speed of a fan, or in various other applications where current control is necessary.

Information Booster:

• Rheostat Function: The rheostat typically has a slider or dial that changes the length of the resistor, adjusting the amount of current flowing through the circuit. It is commonly used in electrical devices to fine-tune the flow of electricity.
• Types of Resistors:
• Fixed Resistor: Offers a constant resistance.
• Variable Resistor (Rheostat): Allows for the resistance to be varied, adjusting the current flow.

Additional Knowledge:

• A galvanometer is used to detect and measure small currents.
• An ammeter measures the current flowing through the circuit.
• A voltmeter measures the potential difference (voltage) across two points.