Question

A defibrillator is a device that sends an electrical shock to maintain heart rhythm if a person goes into cardiac arrest. If a defibrillator passes 15 A of current through the torso of a person in 2 ms, the number of electrons passed to the person is
1. 0.67 × 107 electrons
2. 1.88 × 10⁷ electrons
3. 2.12 × 107 electrons
4. 4.55 × 107 electrons

Answer 1

Correct Answer - Option 2 : 1.88 × 10⁷ electrons

The correct answer is option 2) i.e. 1.88 × 107 electrons

CONCEPT:

• Electric charge is a fundamental property of matter that causes the matter to experience a force when kept in electric and magnetic fields.
  • There are two types of charges possessed by matter - negative charge and positive charge.
  • The matter that is neither positive nor negative is said to be neutral.
  • The electric charge of the matter comes from the charge carried by electrons and protons at the atomic level.
  • The SI unit of electric charge is Coulomb (C).

• Electric current is defined as the charge flowing per unit time.

It is given by:

\(I = \frac{q}{t}\)

Where I is current, q is the charge and t is the time.

CALCULATION:

Given that:

Current, I = 15 A

Time, t = 2 ms = 2 × 10^-3 s

Using \(I = \frac{q}{t}\),

The total charge passed to the person, q = It = 15 × 2 × 10-3 = 30 × 10-3 C

Charge of an electron = -1.6 × 10^-19 C

Number of electrons in 30 × 10^-3 C = \(\frac{30 × 10^{-3}}{1.6\; \times\; 10^{-19}} = 1.88 \;\times\; 10^{17}\)