A charge q moves from point A to point B in an electric field. The potential energy of the charge at point A is 5.6 × 10-10 joules and that at point B is 2.3 × 10-10 joules. If the kinetic energy at point A is zero, what is the kinetic energy at point B?

5.6 × 10-12 joules

1.3 × 10-12 joules

2.3 × 10-12 joules

3.3 × 10-10 joules

5.6 × 10-10 joules

For the law of conservation of energy, the loss in electrical potential energy of the charge must be equal to the gain in kinetic energy of the particle:

\(U_A-U_B = K_B-K_A\)

the kinetic energy of the charge at point A is zero: \(K_A=0\), so we can immediately find the kinetic energy of the charge at point B:

\(K_B=U_A-U_B=5.6\cdot 10^{-10} J-2.3\cdot 10^{-10} J=3.3\cdot 10^{-10} J\)

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itemderby itemderby · Answer 2 · 2019-02-19T05:28:33-05:00

Answer: Option (d) is the correct answer.

Explanation:

According to work energy theorem, total work done on an object equals to the change in objects kinetic energy and change in potential energy.

Mathematically, \(\Delta Kinetic energy = -\Delta Potential energy\)

It is given that potential energy at point A is \(5.6 \times 10^{-10}\) joules and at point B it is \(2.3 \times 10^{-10}\) joules.

Also, kinetic energy at point A is zero and at point B we will calculate the kinetic energy as follows.

\(\Delta Kinetic energy = -\Delta Potential energy\)

\(K.E_{B} - K.E_{A}\) = \(-[P.E_{B} - P.E_{A}]\)

\(K.E_{B} - 0\) = \(-[2.3 \times 10^{-10} - 5.6 \times 10^{-10}]\)

= \(-( -3.3 \times 10^{-10})\) joules

= \(3.3 \times 10^{-10}\) joules

Thus, we can conclude that kinetic energy at point B is \(3.3 \times 10^{-10}\) joules.