Question

In a neon gas discharge tube $N{e}^{+}$ ions moving through a cross-section of the tube each second to the right is $2.9\times {10}^{18}$, while $1.2\times {10}^{18}$ electrons move towards left in the same time; the electronic charge being $1.6\times {10}^{-19}C,$ the net electric current is

• A. $0.27A$ to the right
• B. $0.66A$ to the right
• C. $0.66A$ to the left
• D. $zero$

Answer 1

The correct option is B $0.66A$ to the right

charge moving towards right due to positive ions

$Q_{+ve}=2.9\times {10}^{18}\times 1.6\times {10}^{-19}=0.464C$

charge moving towards left due to electron

$Q_{-ve}=-1.2\times {10}^{18}\times 1.6\times {10}^{-19}=0.192C$

total positive charge moving through a cross section area towards right will be

$Q=0.464-(-0.192)=0.656=0.66C$

as positive charge is moving towards right so current will have same direction

and

$I=\frac{Q}{t}=\frac{0.66C}{1sec}=0.66A$