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Here,
Number of electrons, n = 10²⁰
Charge on each electron,  e = 1.6 x 10^–19 C
Time, t = 0.1 s 

$\therefore$ Total charge, Q = ne
                            = 10²⁰ x 1.6 x 10^–19 
                            = 16

Current flowing through the conductor , $\mathrm{I} = \frac{\mathrm{Q}}{\mathrm{t}} = \frac{16}{0.1} = 160 \mathrm{A}.$

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 Maintenance of current in an electric circuit: The flow of electric current in a circuit is similar to the flow of water in a pipe. Fig, shows a closed water system consisting of a pump P, which builds up and maintains pressure to lift water from a tank B to the reservoir A, through the pipe R.
The different points along the pipe are at different pressures, Water in the pipe will flow from a point C to D only when the pressure at C is greater than that at D. So, when the valve V is open, water would start flowing into the reservior A
Similarly, electrons will move along wire, if there is a difference of electric pressure, called potential difference along the conductor. This potential difference is produced by a cell or a battery through a chemical reaction.

Fig. Mechanical analog of electric current.

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Charge, Q = 1500 C
Time for which the charge is flowing, t = 5 min
Current in the wire, I = Q / t

                                = $\frac{1500}{5\times 60} = 5 A$

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Time for which charge is passing throught he lamp, t = 2 min = 2$\times 60$ = 120 sec 
Current flowing through the lamp, I = 300 mA
Therefore, 
Charge, Q = It
                = 300 $\times {10}^{-3}$ $\times 120$

                = 36,000 $\times {10}^{-3}$ 

                = 36 C

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Given, 
Number of electrons = 10⁹
Therefore, 
Total charge on the electron, q = ne
                                               = ${10}^9\times 1.6\times {10}^{-19}$ 
                                               = 1.6 $\times$$\times$ 10^-10 
So, 
Current through the wire is given by, $\mathrm{I} = \frac{\mathrm{q}}{\mathrm{t}}$
That is,
               I = $\frac{1.6 \times {10}^{-10} }{{10}^{-3}} = 1.6 \times {10}^{-7} A$

The direction of current is opposite to the direction of electron. Hence, it is from Q to P.