s'why electricity makes yer head hurt!
rheostats are measured in watts, and are "valves to control current"
you vary the
apparent voltage by controlling the current - the voltage in yer portable electric heater isn't varying when the element gets hot, the element is 'dissipating' the current - the motor requires a certain amount of current to turn at a given speed because of it's internal resistance - you can change the speed by reducing the voltage
or increaseing the resistance to reduce the current - battery voltage remains constant, so we introduce resistance to decrease current down the line - yer right, current is the work done, ie: heat, volts is
potential work, but doesn't travel, current does
the rheostat on the switch varies resistance so the motor can't turn at full speed - haven't dropped the voltage, but increased the resistance - you might look at it that the switch is 'dropping the voltage', because the rest of that pie is E=IxR - it's still the current that creates the heat - same amount of work [heat] in the circuit, but some of it is in heat generated by the motor, some is heat generated by the rheostat, at full speed the motor generates all the heat - that's why the adapters for running 6V things off 12V come mounted on big ceramic blocks, to dissipate the excess 'potential' as current generated heat :confused: so that's why the motor goes round and the switch gets hot
Bill
