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How well a MOSFET transistor conducts between it’s Drain and Source pins is determined by the voltage at it’s Gate pin.
The N channel enhancement mode MOSFET needs a high enough Gate voltage in order for it to conduct from Drain to Source. That is when it is considered as being turned on, and when the load on the Drain side will be powered.
In the simplest switch circuit, you can just connect the Gate directly to the positive supply that is also powering the load on the drain side of the circuit.
The N channel enhancement mode MOSFET Drain to Source doesn’t conduct when there is a low enough voltage to the Gate. The transistor and it’s load are turned off.
Easiest way to turn the N channel enhancement mode transistor off is to connect it’s Gate to the negative supply voltage that the Source is connected to.
I got my 2N7000 N channel enhancement mode MOSFET transistors from the Joe Knows Electronics Semiconductor kit. Shown in the affiliate link above.
No current flows in or out of the Gate, although a small amount of current does move briefly while the gate’s charge changes. Therefore you can connect the Gate directly to a supply voltage. But it is better to have a series resistor or either a pull up or pull down resistor to help avoid a voltage spike that could fry the Gate. Your body has the potential to build up enough static charge to fry many MOSFET based components and integrated circuits.
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