The mean free path for a gas, with molecular diameter $d$ and number density $n$ can be expressed as : (1) $\frac{1}{\sqrt{2} n^{2} \pi d^{2}}$ (2) $\frac{1}{\sqrt{2} n^{2} \pi^{2} d^{2}}$ (3) $\frac{1}{\sqrt{2} n \pi d }$ (4) $\frac{1}{\sqrt{2} n \pi d^{2}}$

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The mean free path for a gas, with molecular diameter $d$ and number density $n$ can be expressed as : (1) $\frac{1}{\sqrt{2} n^{2} \pi d^{2}}$ (2) $\frac{1}{\sqrt{2} n^{2} \pi^{2} d^{2}}$ (3) $\frac{1}{\sqrt{2} n \pi d }$ (4) $\frac{1}{\sqrt{2} n \pi d^{2}}$

Correct option: 4)

In physics, the mean free path is the average distance over which a moving particle’s direction or energy changes significantly, usually as a result of one or more successive collisions with other particles.

The mean free path for gas is given by $\lambda=\frac{1}{\sqrt{2} \pi nd ^{2}}$

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Two cells of voltage 10V and 2V and internal resistances 10Ω and 5Ω respectively are connected in parallel with the positive end of the 10V battery connected to the negative pole of 2V battery. Find the effective voltage and effective resistance of the combination.

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