07 Electric Current

# 07 Electric Current - Electric Current Any electric charge...

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Unformatted text preview: Electric Current Any electric charge placed in electric field F experiences an electric force = q × F F q If there is a potential difference between two points, the electric field exists in the space between them Electric Field makes mobile charges moving F q If the charge is “free” or “mobile”, then in the electric field it would move (“drift”) pushed by the electric force. The charge drift velocity, v = μ × F, Here μ is a coefficient called “mobility” Electric Field causes Electric Current in conductors F q “Conductor” is any material that contains a lot of “free” or “mobile” charge. When a conductor is placed in an electric field, the mobile charges in it start moving (“drifting”). Moving mobile charges form an electric current Electric Current s Electric current is the rate of electric charge transfer. s Electric current is measured as the charged transferred through any cross- section of the conductor per unit time t Q I Δ Δ = Δ Q is the charge crossing the reference plane of a conductor per time Δ t q Electric Current Example 1 If each marble is charged and carries the electric charge 0.1 C and 10 marbles pass through the open end of the tube per 1 second, the current is ( ) 0 1 10 1 1 1 C Charge I C s A Time s × = = = = . / 1 1 A C s = / Current is measured in Amperes: Electric Current Example 2 Consider a nano-tube filled with a fluid. The fluid contains positively charged mobile molecules. There are 10 5 charged molecules per 1 cm of the nano-tube length. Each molecule has a charge of +1.6 × 10-19 C. In applied field, the molecules move with the drift velocity v = 10 3 cm/s....
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07 Electric Current - Electric Current Any electric charge...

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