Electricity and Magnetism

# Electric potential

Two large, parallel conducting plates are $$d = 10 \text{ cm}$$ apart and have charges of equal magnitude and opposite sign on their facing surfaces. An electric field of strength $$E = 4.00 \times 10^4 \text{ N/C}$$ acts on an electron placed anywhere between the two plates. (Neglect fringing.) What is the potential difference between the plates?

A uniform electric field of $$200 \text{ N/C}$$ points to the left as shown in above figure. When the distance between points $$A$$ and $$B$$ is $$d= 5 \text{ cm},$$ what is the difference in potential $$V_A - V_B$$ between points $$A$$ and $$B?$$

A charge of $$6.0 \text{ nC},$$ is initially at a point that is $$r_1 = 3.0 \text{ m},$$ away from a charge of $$1.0 \text{ nC}$$ moves further away to a point where the distance is $$r_2= 7.0 \text{ m}.$$ What is the approximate potential difference between the two points.

Assume that electric constant is $$\epsilon_0 = 8.9 \times 10^{-12} \text{ F/m}.$$

A 9V battery has an electric potential difference of $$9~\mbox{V}$$ between the positive and negative terminals. How much kinetic energy in J would an electron gain if it moved from the negative terminal to the positive one?

Details and assumptions

• The charge on the electron is $$-1.6 \times 10^{-19}~\mbox{C}$$.
• You may assume energy is conserved (so no drag or energy loss due to resistance for the electron).

As shown in the above figure, three point charges $$q_1 = 2.0 \text{ nC}, q_2 = 5.0 \text{ nC}$$ and $$q_3 = 4.0 \text{ nC}$$ are placed at the three corners of a square with side length $$d = 7 \text{ m}.$$ Find the approximate potential at the point $$A.$$

Assume that electric constant is $$\epsilon_0 = 8.9 \times 10^{-12} \text{ F/m}$$ and $$\sqrt{2}$$ is $$1.4.$$

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