Electromagnetic...

Assertion In electric circuits, wires carrying currents in opposite directions are often twisted together.
Reason If the wires are not twisted together, the combination of the wires forms a current loop, The magnetic field generated by the loop might affect adjacent circuits or components

Assertion The induced e.m.f. and current will be same in two identical loops of copper and aluminium when rotated with same speed in the same magnetic field.
Reason Induced e.m.f. is proportional to rate of change of magnetic field while induced current depends on resistance of wire.

Assertion Inductance coil are made of copper.
Reason Induced current is more in wire having less resistance.

Assertion When two coils are wound on each other, the mutual induction between the coils is maximum.
Reason Mutual induction does not depend on the orientation of the coils.

Assertion An aircraft flies along the meridian, the potential at the ends of its wings will be the same.
Reason Whenever there is change in the magnetic flux e.m.f. induces.

Assertion A spark occurs between the poles of a switch when the switch is opened.
Reason Current flowing in the conductor produces magnetic field.

Assertion In the phenomenon of mutual induction, self-induction of each of the coils persists.
Reason Self-induction arises when strength of current in same coil changes. In mutual induction, current is changing in both the individual coils

Assertion Lenz\'s law violates the principle of conservation of energy.
Reason Induced e.m.f. always opposes the change in magnetic flux responsible for its production.

Assertion The back e.m.f. in a dc motor is maximum when the motor has just been switched on.
Reason When motor is switched on it has maximum speed.