Answer:
a) If I increase the number of moving charged particles per cubic meter in a conductor, I will have to increase the cross sectional area of the conductor to get the same amount of current for the same electric field in the conductor.
FALSE
As we know that
so here if we increase the number of charge per unit volume then we need to decrease the area to get same amount of current through the wire.
b) The change in magnetic flux in a closed loop induces an EMF that opposes the change in magnetic flux.
TRUE
As per lenz law the direction of induced EMF is always opposite to the change in the flux due to which EMF is induced in the closed loop.
c) The magnetic force per unit length of two long, parallel, current-carrying conductors is repulsive if the currents are flowing in the opposite direction.
TRUE
When magnetic field of first wire will interact with other then it will exert force on it
so here the force will be on other wire such that the two wire will repel when current in the two wires is opposite in direction.
d) . The total magnetic flux through a closed surface is equal to μ0I enclosed
FALSE
magnetic flux is the number of field lines passing through a given area
So it is given as