2. Elecrical quantities.

2.1. Voltage or potential difference.
The amount of energy that a generator can transfer to electrons depends on its voltage (V) or electric tension. This is measured in Volts (V).

If we want to measure voltage, we can use a voltemeter. This device has two wires that must be connected in parallel to the element that we are checking.


2.2. Measuring electrical current.
Electric current (I) is the charge or number of electrons that flow through the cross-section of a connductor every second.
                                    I = Q/t

Electric current is measured in amperes or amps  (A) in the international System or SI.

2.3. Electrical resistance: Ohm's Law.

CIRCUIT          VOLTAGE             ELECTRIC CURRENT             V/I  
      A                     3V                              30 mA                                 100
      B                     6V                              60 mA                                 100
      C                     9V                              90 mA                                 100

The resistance (R) of a material is equal to the volatge divided by the intensity of the electric current which travels through the material. The ratio, which is called Ohm's Law can be expressed as follows:
          R= V/I

2.4. Electrical energy and power.

• Electrical energy: if an electric current flows at a particular tension for a certain amount of time, we can calculate the energy that is consumed E = V x I x t
• Electric power: P = VxI