Current Electricity: Electric Current

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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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