What is electrical resistivity of a material? What is its unit? Describe an experiment to study the factors on which the resistance of conducting wire depends.
Resistivity is numerically equal to the resistance of a wire of unit length having an unit area of cross-section. Its unit is ohm metre $( \Omega \, m)$. Mention the dependence of resistance on length and area of cross section of the wire giving details of experiment using a circuit diagram.
What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.
Mention the condition under which charges can move in a conductor. Name the device which is used to maintain this condition in an electric circuit.
There are two electric bulbs, $(i)$ marked $60\, W$, $220\, V$ and $(ii)$ marked $100 \,W , 220 \,V .$ Which one of them has higher resistance ?
What is meant by "electrical resistance" of a conductor ? State how resistance of a conductor is affected when $(i)$ a low current passes through it for a short duration; $(ii)$ a heavy current passes through it for about $30$ seconds.
What are the conditions under which $Ohm's$ law is not obeyed ?