Rankers Physics
Topic: Current Electricity
Subtopic: Basics of Current

10,000 alpha particles per minute are passing through a straight tube of radius r. The resulting electric current is approximately :  
\[0.5\times 10^{-16} amp\]
\[2\times 10^{12} amp\]
\[0.5\times 10^{12} amp\]
\[2\times 10^{-12} amp\]

Solution:

Let’s solve the problem step by step:


1. Key Concepts

  • Alpha particles (α\alpha) have a charge of qα=2eq_\alpha = 2e, where e=1.6×1019Ce = 1.6 \times 10^{-19} \, \text{C} is the elementary charge.
  • Electric current II is the rate of flow of charge: I=Total charge passingTimeI = \frac{\text{Total charge passing}}{\text{Time}}

2. Total Charge Passing per Minute

We are given:

  • N=10,000α N = 10,000 \, \alpha-particles per minute,
  • Each α\alpha-particle carries a charge qα=2e=2×1.6×1019=3.2×1019Cq_\alpha = 2e = 2 \times 1.6 \times 10^{-19} = 3.2 \times 10^{-19} \, \text{C}.

The total charge passing in 1 minute is:

Q=Nqα=10,0003.2×1019=3.2×1015C.Q = N \cdot q_\alpha = 10,000 \cdot 3.2 \times 10^{-19} = 3.2 \times 10^{-15} \, \text{C}.


3. Current

Convert the time from minutes to seconds:

t=60seconds.t = 60 \, \text{seconds}.

The current is:

I=Qt=3.2×101560=0.533×1016A.I = \frac{Q}{t} = \frac{3.2 \times 10^{-15}}{60} = 0.533 \times 10^{-16} \, \text{A}.

Rounding off, the current is approximately:

0.5×1016A.\boxed{0.5 \times 10^{-16} \, \text{A}}.

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