Electricity

An electric current is a flow of ELECTRONS flowing through wires and electronic components.

It can be compared to the flow of water through pipes and radiators, etc. As water is pushed through pipes by a pump, electric current is pushed through wires by a battery or power supply. # 1

A basic law of the Universe is that like charges repel each other and unlike charges attract each other. An electron has a negative charge. It repels other electrons. #’s 2 & 3

CONDUCTORS are materials in which it is easy to get electrons to move and provide a flow of electric current. Conductors are mostly metals such as gold, silver, copper, iron and lead. #’s 4 & 5

Metals are not perfect conductors and offer some resistance to the flow of current. The resistance of a conductor (such as a metal rod) is determined by three things: (1) its length. The longer its length the higher its resistance. (2) its cross-sectional area. The bigger this is the lower is its resistance.. (3) the material of which it is made # 6

The negative (-) terminal of a battery will push negative electrons along a wire. The positive (+) terminal of a battery will attract negative electrons along a wire. #’s 7 & 8

AN ELECTRICAL CIRCUIT The route along which the electricity flows is called an electrical circuit. An electrical circuit must be a continuous closed loop. # 9

The circuit shown below has a power source, fuse, switch, two lamps and wires connecting each into a loop or circle. When the connection is complete, current flows from the negative terminal of the battery through the wire, the fuse, the switch, another wire, the lamps, a wire and to the positive terminal of the battery.

The illustration below has a horn in place of the lamp. Any device such as a lamp, horn, wiper motor, or rear window defogger, that consumes electricity is called a load. # 10

In an electrical circuit, all loads are regarded as resistance. Loads use up voltage and control the amount of current flowing in a circuit. Loads with high resistance cause less current to flow while those with lower resistance allow high current rates to flow. #’s 11,12, &13

Electrical Terms Current: The flow of electric charge through a wire or any conductor. Measured in amperes. Voltage: The push that causes electrical charges to flow through a conductor. Measured in volts. Resistance: Tendency of a material to oppose electron flow and change electrical energy into thermal energy and light. Measured in Ohms. #’s 14,15, 16, 17, & 18

WHAT IS OHM'S LAW? A simple relationship exists between voltage, current, and resistance in electrical circuits. Understanding this relationship is important for fast, accurate electrical problem diagnosis and repair.

When voltage is applied to an electrical circuit, current flows in the circuit. According to Ohms law, the current in a circuit equals the voltage difference divided by the resistance. Consequently, as the resistance in a circuit increases, the current decreases. This relationship is called Ohm's law, and can be expressed as follows: I = V/R Current (I) = Voltage (V) / Resistance (R) # 19,20

APPLICATIONS OF OHM'S LAW As an application of Ohm's law, any voltage V, current I or resistance R in an electrical circuit can be determined without actually measuring it if the two others values are known. This law can be used to determine the amount of current I flowing in the circuit when voltage V is applied to resistance R. As stated previously, Ohm's law is: Current = Voltage / Resistance.