Def: Ohm’s law: for a metal resistor at a constant temperature,

Resistance = voltage

                   current

 

In symbols, R = V or V = I.R

                        I

 

	Resistance is measured in Ohm’s
	The Ohm is named after Georg Ohm

 

 

	When resistors are connected in series, the total resistance is obtained by adding the individual resistances (R= R1 + R2)
	Power is measured in watts (w)
	James Watt contributed to the development of the steam engine as a practical power source.

 

Def: A device that uses energy of 1 joule per second has a power of 1 watt.

 

·        The ESB uses the unit of energy called the kilowatt hour.

·        Kilowatt hours = kilowatts x hours

·        Watts = amperes x volts