An instrument can measure the electric current called an ammeter. To measure current ammeter must connect in series with the circuit whose current is to be measured.

The measurement of current through the resistor by using an ammeter is shown in the below figure.

The electric current can also be measured using a galvanometer. The galvanometer gives both the direction and the magnitude of the electric current.

The current can be measured by detecting the magnetic field associated with the current without breaking the circuit. There are various instruments used to measure the current without breaking the circuit.

• Hall effect current sensor transducers
• Current transformer (CT) (Only measure AC)
• Clamp-on meter
• Shunt resistors
• Magneto resistive field sensors

An electric current is defined as a stream of charged particles such as electrons or ions that run through an electric conductor or space. Flow charge rate using a conducting medium with respect to time. Electricity is expressed mathematically (eg in formulas) using the symbol “I” or “i”. The current unit says ampere or amp. This was revealed by A.

In other words, a stream of charged particles flowing into an electrical conductor or space is known as an electric current. Charging moving particles are called charging carriers which may be electrons, holes, ions, etc.

The current flow depends on the conductive medium, below are conductive material examples

• In a conductor, the current flow is due to electrons.
• In semiconductors, the current flow is due to electrons or holes.
• In the electrolyte, the current flow is due to ions as well
• In plasma-ionized gas, energy flows are caused by ions and electrons.

When a potential voltage difference is used between two points in a conductive medium, the electrical energy begins to flow from high power to low power. The higher the voltage or the potential difference, the more current flows between the two points.

If two points in a cycle have the same force, then the current cannot flow. The magnitude of the current depends on the voltage or potential difference between the two points. Therefore, we can say that the current is the result of voltage.

Electric power can generate electric fields, which are used in inductors, transformers, generators, motors. In an electric conductor, the current causes an opposing heat or joule heat that creates light in an incandescent lamp.

SI unit of current

The SI unit for current is ampere or amp. This is represented by A. Ampere, or amp is the base SI unit of electric current. The unit ampere is named in honor of the great physicist Andrew Marie Ampere.

In the SI system, 1 ampere is the flow of electric charge between two points at the rate of one coulomb per second. Thus,

Hence current is also measured in coulomb per second or C/S.

Electric Current Formula

The basic formulas for current are:

1. The relationship between Current, Voltage and Resistance (Ohm’s Law)
2. The relationship between Current, Power and Voltage
3. The relationship between Current, Power and Resistance

Current Formula 1 (Ohm’s Law)

According’s to ohm’s law,

Thus,

Current Formula 2 (Power and Voltage)

The Power transferred is the product of supply voltage and electric current.

Thus, we get current equals the power divided by voltage. Mathematically,

Where stands for amperes or amps (the units for electric current).

Current Formula 3 (Power and Resistance, Ohmic Loss, Resistive Heating)

We know that,

Now put in the above equation we get,

Thus, the current is the square root of the ratio of power and resistance. Mathematically,

Dimensions of Current

Dimensions of current in terms of mass (M), length (L), time (T), and ampere (A) is given by .

Current (I) is a representation of the coulomb per second. Thus,