Resistance to changing in magnetic field at wire I want to know if there is resistance to changing in magnetic field at wire? Sure I know Lenz's law but it works "only" on a spiral wire and circles, but does it work on straight wires too?
 A: Faraday's law states that the induced EMF in a wire due to changing magnetic field is given by: 
$$
V= -\frac{\mathrm dΦ}{\mathrm dt}\text{ and }Φ= BA\cosθ.
$$
$A$ is the area enclosed by the circuit. Portions of the wire can be straight and you will still have an area enclosed, so there will still be induced EMF, but at some point, for it to be a closed circuit, the wire needs to form a loop. If you have a straight wire (not in a circuit) in a changing magnetic field there will be no induced EMF because there is no enclosed area.
A: Lenz's law is concerned with the conservation of energy and the opposition to a change producing "it" is in terms of the induced current not the induced emf.
So if there is an induced emf but that induced emf does not produce an induced current there is no opposition to the motion producing the induced emf.  
A wire moving at constant velocity in a uniform magnetic field will have a (motional) emf induced in it.
If there is a complete circuit achieved by having the wire slide over a U-shaped conductor a current flow, an external force needs to be applied on the wire to keep it moving at constant velocity.
Remove that force and the speed (kinetic energy) of the wire decreases and heat is generated in the U-shaped conductor.
