The supply device must have an output voltage that matches that of the load, and a current rating that exceeds that of the load. So you cannot use a load that draws 2 A from a supply device that is rated at only 1 A.
No. Your power supply must be able to supply rated voltage (12 volts) and rated current (3 amps).
No it will not. The adapter with an output voltage of 7.5 volts will not even come close to operating a device that requires a 75 volt supply. The best thing you can try is to find an adapter that will output the 75 volts that the device needs.
A device which requires 1000mA at 9 volts in order to operate will not work from an output of 500mA. This output is only half the power requirement of the device.
No. Usually it's a -/+ 10% difference. So, a 9v would need at least 7.2 volts or more
No, if you use a 6 volts adapter instead of a 9 volts adapter, you will be supplying 3 volts too little to the item that requires 9 volts. Either it may not work properly or it won't work at all. The fact that the 6 volt adapter can supply more current (2000 mA instead of only 1200 mA) won't help solve the problem of having insufficient voltage.
Yes. However, the device me not run at its optimum capacity/speed. Other thing to take into consideration is that the polarity (+/-) of adapter and the receiving device must match.
Well, trying to clarify your question, if you have a device that normally has a 5V 3.6A adapter, than it likely needs to be able to draw up to 3.6 amps or so for the device to operate normally. So, a 5V 2.6 amp adapter may operate at times, but only when the device is trying to draw less than 2.6 amps. If the device tries to draw more than 2.6 amps than you run the chance of burning out your transformer (the AC adapter), or just not having your device work. Both adapters will put out the 5 volts, but the 2.6 amp adapter will not provide enough current. You can safely use a larger adapter than the 3.6A, as your device will only draw as much current at 5 volts as it needs. On another note, do not try an adapter that puts out the same current but more voltage. Such as 7.5 volts 3.6 amps. This will overdrive your device and potentially burn it out.
No, the voltage is wrong. The device needs an adapter that only produces 5 volts. The device that you need may state on it 2500 mA instead of 2.4 amps
Yes, the manufacturer specifies what the working voltage of a device will be and that voltage has to be adhered to.
difference is 2.7 amperes in numbers will be 12 volts 3 amps and the other will be 12 volts .3 amps
Unlikely. 3 volts in stead of 4.5 volts is a too big gap between that it gets and what it expects.
No you can not. The power supply output of 5 volts is under sized. There is no way that a 45 volt device would operate from it. You will need to find a power supply of 45 volts.