Q10 (i) In Figure 3 shown below, all the cells are identical. The external resistance R is also same in both the circuits.



If the same current flows through the resistor R in both the circuits, calculate the relation between r, the internal resistance of each cell and the external resistance R.

OR

(ii) The drift velocity of electrons in a conductor connected to a battery is given by

vd = -eEτ/m.

Here, e is the charge of the electron, E is the electric field, τ is the average time between collisions and m is the mass of the electron.

(a) How does the drift velocity change with an increase in the potential difference across the conductor?

(b) A copper wire of length 'l' is connected to a source. If the copper wire is replaced by another copper wire of the same area of cross-section but of length '4l', how will the drift velocity change? Explain.

Solution

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