Electrical Engineering

It depends on whether the material is ohmic or non-ohmic.

If it is ohmic, then it will obey Ohm's Law, and its resistance will remain constant if the current decreases.

If, on the other hand, it is non-ohmic, it will not obey Ohm's Law and, if the temperature of the conductor falls (assuming it is a metallic conductor) due to the fall in current, then its resistance will fall too.

Generator principle: a current moving relative to a magnetic field will have a voltage induced into it.

Motor principle: a current-carrying conductor within a magnetic field will experience a force that will try to push that conductor out of the field.

it depends the manufaturer standard, nut usaually its above 20 M ohms .

How long is a piece of string? Transformers vary is size hugely, so it's quite impossible to provide a definitive answer to your question. But the resistance of a transformer's windings will be very low -certainly within the ohms or milliohm range, depending on the physical size (cross-sectional area and length) of the conductors. It's most-certainly not in the megohm range, as suggested in the original answer!

Did you mean conventional current or convection current?

As this question is in an Electronics category, I will assume that you meant conventional current.

Conventional current flow is electrical current flow from positive to negative as defined by conventional practicegoing back to Ben Franklin, etc. Note that this is opposite to electron current flow from negative to positive as defined by the physical movement of electrons in conductors, n type semiconductors, and vacuum tubes. Note that this is the same as hole current flow from positive to negative as defined by the physical movement of holes in p type semiconductors.

If by some chance you got the wrong category and did mean convection current; that is cyclic fluid flow driven by a heat differential in a gravitational field. It can happen in any fluid: gas (e.g. air), liquid (e.g. water), or semisolid (e.g. hot rocks of earth's mantle).

Current in a parallel circuit divides between the branches, depending on the relative impedance of each branch. Kirchoff's current law, which can be used to analyze that current, states simply that the sum of the currents entering and leaving a node, properly signed, always add up to zero.

Current in a series circuit is the same at every point in the circuit. This is a consequence of Kirchoff's current law, because a node in a series circuit consists of only two conductors, and the sum of the currents at that node must be zero. By implication, then, all nodes in a series circuit must have the same current.

Not asked, but discussed due to completeness, is Kirchoff's voltage law, which states that the signed sum of the voltage drops around a series circuit always add up to zero. A consequence of this is that the voltage across elements of a parallel circuit must be the same.

In AC electric systems, electrical energy is consumed by resistive loads. An AC generator sends out energy, and a resistive load takes the energy in.

But in AC systems, electrical energy is not consumed by pure capacitor loads. Neither is it consumed by pure inductive loads. Instead these loads reflect all energy back to the generator. They don't consume any electrical energy themselves. Ideally this shouldn't cause problems. However, in the real world a pure capacitor load will cause the power lines to become warm. While the energy flows out and back, there is an electric current in the lines. The same thing also happens with a pure inductive load. The loads reflect all energy and consumes none, but the utility company must use up fuel to keep sending out the reflected power and warm the power lines.

If large industrial customers place inductive or capacitive loads on the power grid, the utility company installs special electric meters to measure this. The electric company then charges them a fee. The industrial customer must pay for the energy losses they cause in the warm power lines.

In AC electrical mathematics, the reflected power effect is described as REACTIVE POWER, and is measured in terms of POWER FACTOR. A resistive load consumes the incoming energy, and it has a power factor of 100%. On the other hand, pure capacitors and inductors reflect all the incoming energy, and they have a power factor of 0%.

There is a way for industrial customers to fix the problem. There is a way to correct the power factor and bring it to 100%. If the customer is using an inductive load, they can place just the right value of capacitor across that load. The energy then stops reflecting back to the electric company generators. No longer do the power lines suffer excess heating. The electric company measures this, then stops charging the extra fee. (Actually the energy still reflects back and forth between the inductive load and the added capacitor. The excess heating in those short local wires is insignificant.)

Since large industrial customers commonly use AC motors containing coils, they commonly create inductive loads on the power grid. Power-factor correcting capacitors are the solution. They eliminate the extra fee charged by utility companies, so a PFC capacitor will eventually pay for itself. However, such capacitors cannot save money for individual homes or small businesses. These customers don't have the special electric meters, and the utility companies aren't charging any special fees for bad power factor. Those PFC capacitors don't save any money, and can never pay for themselves.

Power factor is the cosine of a circuit's phase angle, i.e. the angle by which the load current lags or leads the supply voltage. When they are in phase (phase angle is zero), the power factor is unity (i.e. 1); when they are 90-degrees out of phase, the power factor is zero. 'Poor' power factor (i.e. when it is closer to zero than to unity) results in excessively-high currents for a given value of load; power-factor correction (or 'improvement') acts to move the power-factor towards unity, thus reducing the value of that load current. This is desirable, as it reduces the necessary amount of copper (i.e. the cross-sectional area) of conductors and other equipment supplying the load. For inductive loads, power-factor correction is achieved through the use of capacitor banks.