What length of copper wire of specific resistance 1.7 x 10^-8 Ω m and radius 1 mm is required so that it's resistance is 2 Ω.

The filament of a bulb takes a current 100 mA when potential difference across it is 0.2 V. When the potential difference across it becomes 1.0 V, the current becomes 400 mA. Calculate the resistance of filament in each case and account for the difference.

The emf of a cell depends on :

1. the material of electrodes
2. the shape of electrodes
3. the distance between the electrodes
4. the amount of electrolyte in the cell

Emf of a cell is …………… the terminal voltage when cell is not in use, while …………… the terminal voltage when cell is in use.

1. greater than, smaller than
2. smaller than, greater than
3. equal to, greater than
4. equal to, smaller than