you need
  • textbook on physics, a sheet of paper, a pencil, an ammeter, voltmeter.
Guide
1
Remember, using a textbook on physics, as determined by the current from Ohm's law.The ratio of the current law is defined as the ratio of the voltage on the circuit resistance of the site.Thus, one reason for changing the current may be a change in either the voltage or the impedance circuit element.
2
And the situation, leading to a change of one or another parameter may be different.For example, if you have a classic voltage divider comprising two resistive elements, the voltage changes on one of them immediately change the voltage at the other, and hence change and current.The reason that led to a change in voltage, a change in resistance of a resistor or a change in the total supply chain.
3
Please note that, in
practice, often changing currents in circuits due to the mismatch required supply voltage.You can use an ammeter to measure the current value of any of its home device.Then check against this value with the stated instructions.If you notice a discrepancy, then measure the voltage in the network, you will notice that it is not equal to 220, which led to a change in the current.
4
Also note that the current changes in the various instruments at its aging.In this case, the mechanism of reduction or the instability of the current associated with a variety of factors.One of them is the deterioration of the contacts, which leads to an additional voltage drop in the circuit at this contact and reduce the current.Another reason, usually, is the chemical composition of the resistive elements and the change of state between the capacitor plates, when they are present in the circuit.
5
See diagram of the device, the currents in which you are interested.Almost every modern appliance contains transistors.This three-electrode semiconductor elements.Their peculiarity lies in the fact that the current through a contact depends on the voltage applied to the other track, the relationship is very strong.Indeed, this property of the semiconductor element, and is used in its application, but it also causes undesirable changes in the device.Also worth noting is that the continuous use of the device, comprising transistors, it is extremely hot.As is known, the temperature variation semiconductor causes a sharp change of resistance.