There isn't one single instrument used for *all* aspects of electrical current. We use different instruments to measure, control, and manipulate current depending on what we're trying to do. Here are some examples:

For measuring current:

* Ammeter: This is the most common instrument used to measure the amount of current flowing through a circuit.

* Multimeter: This versatile instrument can measure current, voltage, and resistance.

For controlling current:

* Resistor: This component limits the amount of current flowing through a circuit.

* Switch: This component can open or close a circuit, effectively controlling the flow of current.

* Fuse: This safety device protects circuits by breaking the circuit if the current gets too high.

* Circuit breaker: Similar to a fuse, but can be reset after a break.

For manipulating current:

* Transformer: This device changes the voltage of an alternating current (AC) without changing the power.

* Diode: This component allows current to flow in one direction only, which can be used to rectify AC current into DC current.

* Transistor: This component acts as a switch or amplifier, controlling the flow of current based on a small input signal.

So, the "instrument" for electrical current depends on the specific task you're trying to accomplish.