In metals, such as copper, the positive ions are relatively immobile since they are fixed in a regular array called a lattice. Metal ions are always positive, being formed from atoms that lose one or more electrons. These free electrons wander through the positive ion lattice, and it is these negative charges that gives metals there conducting properties. Fig. 2. In a metal, the current is due to the movement of free electrons through a lattice of positive metal ions. Common currents current in mobile phone antenna ~ 10 nA (1 nA = 10-9 A) mobile phone ~100 mA (1 mA = 1x10-3 A) incandescent light globe ~ 1 A car battery ~ 10 A electric radiator ~ 15 A lightning ~ 1 MA (1 MA = 106 A) 1 A = 1 C.s-1 flow of 6.24x1018 electrons.s-1 The unit of current, the ampere takes its name from Andre-Marie Ampere, a French scientist of the early 19th century. In the S.I. System of units, the ampere is the fundamental (base) unit for electromagnetism. Other units such as coulomb are derived units. The most commonly used current-measuring devices are called ammeters. Their operation depends upon the torque produced by a magnet on a current-carrying conductor.
In metals, such as copper, the positive ions are relatively immobile since they are fixed in a regular array called a lattice. Metal ions are always positive, being formed from atoms that lose one or more electrons. These free electrons wander through the positive ion lattice, and it is these negative charges that gives metals there conducting properties. Fig. 2. In a metal, the current is due to the movement of free electrons through a lattice of positive metal ions. Common currents current in mobile phone antenna ~ 10 nA (1 nA = 10-9 A) mobile phone ~100 mA (1 mA = 1x10-3 A) incandescent light globe ~ 1 A car battery ~ 10 A electric radiator ~ 15 A lightning ~ 1 MA (1 MA = 106 A) 1 A = 1 C.s-1 flow of 6.24x1018 electrons.s-1 The unit of current, the ampere takes its name from Andre-Marie Ampere, a French scientist of the early 19th century. In the S.I. System of units, the ampere is the fundamental (base) unit for electromagnetism. Other units such as coulomb are derived units. The most commonly used current-measuring devices are called ammeters. Their operation depends upon the torque produced by a magnet on a current-carrying conductor.