Ohms Law

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Balance Scale representation of OHMs Law

If a weight is removed from the resistance arm on the right of the scale, the needle will swing to the left indicating an increase in current

If the weight is replaced, the scale will swing back to the right moving the needle showing a current increase.

balance scale

The opposite is true for the voltage weights,
A decrease in voltage by removing weights causes the indicator needle to swing to the right or min on the current flow scale.

An increase in voltage will cause the needle to swing left towards the Max indicator on the current flow scale.

balance scale

The diagrams above are illustrations of a very basic and important rule in electrical engineering.

Ohms law.

Ohms law states that

  • For a fixed resistance value (R) the current flow (I) increases in direct proportion to the increase in voltage (V).
  • In a circuit with a fixed resistance the current is directly proportional to voltage applied.
  • If the Voltage is kept constant and the resistance is varied the current flow will be inversely proportional to the resistance.


For Example: -

    • doubling the resistance causes the current to be halved
    • halving the resistance causes the current to be doubled

The formula for Ohms Law is given opposite:

Where:

  • The symbol R indicates resistance in Ohms.
  • The symbol V indicates voltage in Volts
  • The symbol I indicates Current in Amps

The symbol for Ohms is given by the Greek letter Omega.

Symbol =

V = IR

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