Question:
In a neon discharge tube, \( 2.9 \times 10^{18} \, \text{Ne}^{+} \) ions move to the right each second while \( 1.2 \times 10^{18} \) electrons move to the left per second, electrons charge is \( 1.6 \times 10^{-19} \, \text{C} \). The current in the discharge tube is:
In a neon discharge tube, \( 2.9 \times 10^{18} \, \text{Ne}^{+} \) ions move to the right each second while \( 1.2 \times 10^{18} \) electrons move to the left per second, electrons charge is \( 1.6 \times 10^{-19} \, \text{C} \). The current in the discharge tube is:
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The current in a discharge tube can be found by summing the individual currents due to ions and electrons, considering the direction of their movement.
Updated On: Apr 22, 2026
- 1 A, towards right
- 0.66 A, towards right
- 0.66 A, towards left
- zero
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The Correct Option is B
Solution and Explanation
Step 1: Calculate the current.
The current due to ions is given by: \[ I_{\text{ions}} = n \times q \times v \] where,
\( n = 2.9 \times 10^{18} \, \text{ions/sec} \),
\( q = 1.6 \times 10^{-19} \, \text{C} \).
Hence: \[ I_{\text{ions}} = 2.9 \times 10^{18} \times 1.6 \times 10^{-19} = 0.464 \, \text{A} \] Similarly, the current due to electrons: \[ I_{\text{electrons}} = 1.2 \times 10^{18} \times 1.6 \times 10^{-19} = 0.192 \, \text{A} \] Since electrons move to the left, their current will be considered negative. Adding the ion and electron currents: \[ I = I_{\text{ions}} - I_{\text{electrons}} = 0.464 - 0.192 = 0.66 \, \text{A} \] Thus, the current is \( 0.66 \, \text{A} \) towards the right.
Step 2: Conclusion.
The current in the discharge tube is \( 0.66 \, \text{A} \), towards the right, which is option (2).
The current due to ions is given by: \[ I_{\text{ions}} = n \times q \times v \] where,
\( n = 2.9 \times 10^{18} \, \text{ions/sec} \),
\( q = 1.6 \times 10^{-19} \, \text{C} \).
Hence: \[ I_{\text{ions}} = 2.9 \times 10^{18} \times 1.6 \times 10^{-19} = 0.464 \, \text{A} \] Similarly, the current due to electrons: \[ I_{\text{electrons}} = 1.2 \times 10^{18} \times 1.6 \times 10^{-19} = 0.192 \, \text{A} \] Since electrons move to the left, their current will be considered negative. Adding the ion and electron currents: \[ I = I_{\text{ions}} - I_{\text{electrons}} = 0.464 - 0.192 = 0.66 \, \text{A} \] Thus, the current is \( 0.66 \, \text{A} \) towards the right.
Step 2: Conclusion.
The current in the discharge tube is \( 0.66 \, \text{A} \), towards the right, which is option (2).
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