LEARNATHON

III

Competition for grade 6 to 10 students! Learn, solve tests and earn prizes!

Learn more### Theory:

Electric current or simply current (\(I\)) is the rate at which charges flow past a point on a circuit.

*Flow of charges in a wire*

The value of current can be measured and expressed numerically. The SI unit for current is the ampere, and it is denoted as '\(A\)'. The formula is given as,

$\begin{array}{l}\mathit{Current}=\frac{\mathit{Charge}}{\mathit{Time}}\\ \\ I=\frac{Q}{t}\end{array}$

Where '\(I\)' is current, '\(t\)' is the time and '\(q\)' is the amount of charge flowing through the cross-section of a wire in time (\(t\)).

One ampere (\(1\ A\)) is defined as one coulomb (\(1\ C\)) of charge passing through a cross-section of a wire every one second (\(1\ s\)).

Mathematically,

$\begin{array}{l}1\phantom{\rule{0.147em}{0ex}}\mathit{ampere}=\phantom{\rule{0.147em}{0ex}}\frac{1\phantom{\rule{0.147em}{0ex}}\mathit{coulomb}}{1\phantom{\rule{0.147em}{0ex}}\mathit{second}}\\ \\ 1\phantom{\rule{0.147em}{0ex}}A=\phantom{\rule{0.147em}{0ex}}\frac{1\phantom{\rule{0.147em}{0ex}}C}{1\phantom{\rule{0.147em}{0ex}}s}\\ \\ =1\phantom{\rule{0.147em}{0ex}}C{s}^{-1}\end{array}$

**Other units of ampere:**

There are some other units of ampere listed in the table below.

Units | Symbols | In ampere |

kiloampere | \(kA\) | \(10^3 A\) |

Megaampere | \(MA\) | \(10^6 A\) |

milliampere | \(mA\) | \(10^{-3} A\) |

microampere | \(\mu A\) | \(10^{-6} A\) |

Measuring device:

An ammeter is a device that measures the strength of the electric current in an electric circuit.

*An ammeter*

Ammeter is always connected in series in a circuit. The current enters the ammeter by the positive (\(+\)) red terminal and exits through the negative (\(–\)) black terminal.

*Ammeter connection in a circuit with diagram*