Electric Circuit Device for Variable Resistance
The question asks for a device used in electric circuits to alter resistance while keeping the voltage constant. Let's examine the options:
- Fuse: A safety device that protects a circuit from overcurrent by melting and breaking the connection. It has a fixed resistance and is not designed to be adjustable.
- Ammeter: A measuring instrument used to measure the electric current in a circuit. It has a very low internal resistance and is not used to change resistance.
- Voltmeter: A measuring instrument used to measure the electric potential difference (voltage) across two points in a circuit. It has a very high internal resistance and is not used to change resistance.
- Rheostat: A variable resistor. It is specifically designed to allow the adjustment of resistance within a circuit. By changing the length of the resistive wire through which the current flows, its resistance can be varied. This allows control over the current flowing through the circuit, without altering the voltage source.
Therefore, the device that fits the description of changing resistance without changing the voltage source is a rheostat.
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