A piece of wire of resistance 4 Ω is bent through 180° at its mid point and the two halves are twisted together. Then resistance is :
If a wire of radius r is drawn to another wire of radius 2r, the new resistance of the wire will be :
The electric resistance of a certain wire of iron is R. If length and radius are doubled, then :
Resistivity of a conductor depends upon its :
Ohm’s law is not applicable on :
Copper and silicon are cooled from 300 K to 60 K, the specific conductivity :
As shown in figure, the current flowing in 2R resistor is
Conductivity of a super-conductor is :
