Circuit diagram help?
A 6-Watt 12-Volt lightbulb is connected in a circuit with a 1500-Watt 120-Volt coffeemaker, an adjustable resistor, and a 120-Volt power supply. The circuit is designed such that the bulb and coffeemaker operate at the given values, and if the bulb fails, the coffeemaker will still function at these values. What does the circuit look like?
Also, if the resistance of the adjustable resistor is increased, what happens to the brightness of the bulb & to the power dissipated by the coffeemaker?
The coffee machine will be connected to the 120V supply.
The 12V bulb and the adjustable resistor will be connected in parallel with the coffee machine, to the 120V supply. Obviously, if the bulb fails, the current through the resistor will drop to 0, but the machine still works normally.
If the variable resistor is increased in value, the bulb will become dimmer, but the coffee machine remains unaffected.
Just in case you are asked, as values were given:
The bulb, when operating at full brightness, will have a current of (6/12) = 0.5A through it. This is also the current flowing through the resistor.
The resistor will have (120 -12) = 108V across it, so initially will have a resistance of (108 /0.5) = 216 ohms. It will be dissipating (108 x .5) = 54 watts.
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