A20-cm long and 1.0-mm diameter thick copper wire (resistivity 1.7 × 10-8 ωm) is connected across a 3-v battery. the current through the wire is
1-7 a.
2-125 a.
3-693 ma.
4-693 a.
5-789 a.

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e