A battery rated at two amps will put out more than two amps. Its rated output is made to help designers get the most life out of it without losing its efficiency. You can get more than two amps out of a D cell but watch out it may explode or overheat.
that is why they put ratings on batteries.
Your question asked what happens to the excess current.
It stays in the battery. :wink:
The battery only puts out the amount of current the circuit was designed to draw. If you put a LED across the battery without a current limiting resistor the current will continue to increase as the heat will cause thermal runaway. POOF :cry: :shock:
The resistor will limit the current, as it is the highest resistance in the series circuit. Most LEDs are designed to run at less than 5 milliamps of current. (There are exceptions, such as automotive and stop-sign type applications) Also If they are pulsed they can handle more current and therefore more brightness. But then there has to be sufficient time to physically cool down.
If you have a 12 volt battery and want to use a 1 milliamp LED. use ohms law.
R = E/I or 12v / .001a = 12000 ohms or 12kohms
12v/12ohms = 1amp = 1000 milliamps
12v/120ohms = .1amps = 100 milliamps
12v/1200 ohms = .01amps = 10 milliamps
12v/12000 ohms = .001amps = 1 milliamp
Hope this helps your understanding
Second question
What is Impedance?
Impedance is also a form of resistance, but is used to help explain circuits that are used with varying frequency (alternating current) and has much more complex math involved, rather than Direct current.