In order to work safely and efficiently in an electrical environment you must understand the basics of electricity.

Direct current flow.

In a simple circuit as shown opposite in Fig 1,

Electrons are driven from the negative battery terminal, on through Sw1, Lp1 and LP2 before being attracted back through the positive terminal of the battery. An electric current flowing in only one direction as in Fig 1 it is known as DC or direct current flow

Fig 1 a simple circuit in operation

Alternating Current Flow.

When electron current flows first from one terminal through Sw1,in Fig 2, on through Lp1 and out of the other terminal then the current reverses and flows from the second terminal back through Lp1, Sw1 and into the first terminal in a continuous cycle.
This action is known as AC or Alternating Current flow familiar to most people as the power supplied to the home from the Electricity company at 240 volts which alternates at a frequency of 50 cycles per second (50Hz)

Fig 2 Illustrates Alternating Current flow in a simple circuit.

Fig 2

The potential applied to the circuit from the negative terminal of the battery repels the electrons in the circuit.

While the potential at the positive terminal attracts the electrons from the circuit.

Electrons carry a small negative charge and repel each other, They are also repelled from the battery negative terminal.

Since likes repel and opposites attract the electrons are drawn to the positive terminal of the power source.

When no force is applied electrons tend to spread evenly through the circuit in a similar way to water finding its own level in a network of pipes if the pump is turned off.

Alternating voltage is used to power many items including cooker and kettle. In other electrical appliances such as the television, video or stereo, the alternating voltage is reduced and converted to DC before it can be used.

A : - 1 Amp

Milliamp (mA): - one thousandth of an amp ¹/_1,000

Microamp (mA): - one millionth of an amp ¹/_1,000,000