Current in Circuit with Cell and Resistance

Rarely Tested

Current in Circuit with Cell and Resistance

### Formula

$$I=\frac{E}{R+r}$$

### Terminologies

- R β†’ External resistance.

- r β†’ Internal resistance.

### Conditions / Special Cases

Terminal voltage:

$$V=IR$$

### Usage

- Used in cell circuit calculations.

Question 1

A metal wire of cross-sectional area $$0.5\,\mathrm{mm^2}$$ and length $$100\,\mathrm{m}$$ is connected across a battery of e.m.f. $$2\,\mathrm{V}$$ and internal resistance $$1\,\Omega$$. The density, atomic mass and electrical conductivity of the metal are $$6.35\times 10^{3}\,\mathrm{kg\,m^{-3}}$$, $$63.5\,\mathrm{gm/mole}$$ and $$2\times 10^{8}\,\mathrm{mho\,m^{-1}}$$, respectively. Assuming one conduction electron per atom of the metal, the drift velocity (in $$\mathrm{mm\,s^{-1}}$$) of the electrons in the wire is:

[Take Avogadro's number as $$6\times 10^{23}$$ and charge of the electron as $$1.6\times 10^{-19}\,\mathrm{C}$$.]

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