A current flows through, not across, a circuit. And, yes, you can measure it using an ammeter.
You measure current by inserting an amp meter in series with the circuit or using a clamp-on meter to measure current by induction. You measure voltage with a volt meter across the supply. You measure resistance in ohms across the resistance. Luckily all these functions are in the same meter in most cases.
Voltage is impressed across a circuit. Current flows through a circuit.
A voltmeter can be connected in parallel to measure the voltage across a component accurately. This means connecting the voltmeter in a separate branch of the circuit, directly across the component being measured. This allows the voltmeter to measure the voltage without affecting the current flow in the circuit.
In shortg circuit current is infinitive.
To measure the current in the circuit an ammeter is used and it is connected in series
An ammeter measures the amount of current flowing through an electrical circuit. It measures amperage.
A multimeter set to measure current (in amperes) would be used to measure current flowing in a circuit. The multimeter needs to be connected in series with the circuit to accurately measure the current.
Cathode ray oscilloscope(CRO) is a device used to see the voltage across a particular element of your circuit and the wave form can also be seen on CRO. But you actually cannot measure the current using CRO as it is meant to give the voltage levels across any element in eletrically enegized circuit. however Digital Multimeter can do this job. But while using DMM to measure current one thing should be kept in mind that your circuit should be linear so that if you break the circuit to find current in series the current could not change in circuit.
A voltmeter is connected in parallel in an electrical circuit to measure the voltage across a specific component or part of the circuit without affecting the flow of current through the circuit.
To measure current in circuit
An ammeter is used to measure the intensity of current flow in a circuit or branch in a circuit. It is wired in series with the circuit being evaluated to accurately measure the current passing through that specific part of the circuit.
For an ideal current source, this means replace the current source with an open circuit. Resistance can then be calculated across the terminals.