Current Electricity: Electric Current

Electric Current The flow of electric charge Symbol = I Scalar quantity Unit = Ampere Conventional current flows from positive to negative

Q = It Q = charge I = current t = time

Ammeter Used to measure current Connected in series with the component that it is measuring the current of Can be used to compare the conductivity of substances

Effects of an Electric Current

1. Chemical effect Electrolysis To demonstrate this, water can be broken up into its constituent elements, hydrogen and oxygen Example: Electroplating - covering one metal with a thin layer of anoher

2. Magnetic effect To demonstrate this, place a compass near to a circuit When the switch on the circuit is closed and current is flowing, the needle of the compass moves due to the magnetic field created Example: Electromagnets

3. Heating effect Can be demonstrated by setting up a circuit with a heating coil immersed in water Measure the temperature before and after the current flows Example: Filament light bulb

Joules Law The rate of heat production in a conductor is proportional to the square of the current provided its resistance is a constant P = I²R P = power I = current R = resistance

Direct current & Alternating current D.C. - current from a battery - flows in one direction only A.C. - current from the mains supply - continuously changes direction

W = I²Rt W = energy I = current R = resistance t = time

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