1 - Circuit Basics

 

      A simple electrical circuit can be made from just a       few components:

  • A dry cell battery , or power source. This will have a specific voltage or electromotive force (e.m.f.) which is measured in volts.

  • Connecting wires to let the energy flow out of the battery, through the circuit's components and back into the power source. The flow around the circuit is known as current and is measured in amps.

  • Components in the circuit which allow you to see it is working:
    e.g. a lamp , motor or buzzer.

    These devices have different working voltages and resistance values (measured in Ohms). Their resistance will determine how much current flows through it and around the circuit. It is important for the power source to be able to provide this amount of current.

    The relationship between the power source voltage, circuit resistance and the circuit current, is known as Ohm's Law (see below).

In a Circuit,
Ohms Law Says:

Voltage (volts) =
Current
(amps) x Resistance (ohms)


      The power used by a circuit is measured in Watts       and can be found by multiplying the voltage across       the circuit (battery voltage) with the current flowing       around the circuit (see below).


In a Circuit,
the Power is Equal to:

Power (watts) =
Voltage (volts) x Current (amps)