A parallel-plate capacitor is made from two aluminum-foil sheets, each $6.3 \mathrm{~cm}$ wide and $5.4 \mathrm{~m}$ long. Between the sheets is a Teflon strip of the same width and length that is $0.035 \mathrm{~mm}$ thick. What is the capacitance of this capacitor? (The dielectric constant of Teflon is $2.1$.)

A given system has the equipotential surfaces shown in given figure. What are the magnitude and direction of the electric field?

A parallel-plate capacitor is made by placing polyethylene $(\kappa=2.3)$ between two sheets of aluminum foil. The area of each sheet of aluminum foil is $400 \mathrm{~cm}^2$, and the thickness of the polyethylene is $0.3 \mathrm{~mm}$. Find the capacitance.

A square of side $a$ has a charge $+Q$ at each corner. What is the electric potential energy of this system of charges?

Calculate the speed of a proton after it accelerates from rest through a potential difference of 275 V.

A proton has an initial speed of $5.5 \times 10^5 \mathrm{~m} / \mathrm{s}$. (a) What potential difference is required to bring the proton to rest? (b) What potential difference is required to reduce the initial speed of the proton by a factor of $2$ ? (c) What potential difference is required to reduce the initial kinetic energy of the proton by a factor of $2$?

A proton has an initial speed of $4.0 \times 10^{5} \mathrm{m} / \mathrm{s}$. What potential difference is required to bring the proton to rest?

A proton has an initial speed of $4.0 \times 10^5 \mathrm{~m} / \mathrm{s}$. What potential difference is required to bring the proton to rest?

A typical $12~\mathrm{V}$ car battery can deliver $7.5 \times 10^5 \mathrm{C}$ of charge. If the energy supplied by the battery could be converted entirely to kinetic energy, what speed would it give to a $1400~\mathrm{kg}$ car that is initially at rest?

A typical 12-V car battery can deliver $7.5 \times 10^{5} \mathrm{C}$ of charge. If the energy supplied by the battery could be converted entirely to kinetic energy, what speed would it give to a 1400-kg car?

Why does electric current flow between the two electrodes of a lemon battery?

a) The two electrodes have a potential difference maintaining a flow of electrons from an anode to a cathode.

b) The two electrodes have a potential difference maintaining a flow of electrons from a cathode to an anode.

c) A battery attached to the two electrodes creates a potential equivalence between the two different metals.

d) A battery attached to the two electrodes creates a potential difference between the two different metals.

When an electric cell is connected to a circuit, electrons flow away from the negative terminal in the circuit. But within the cell, electrons flow $\it{to}$ the negative terminal. Explain.

The electrostatic work done on a particle carrying charge q as the particle travels from point A to point B in an electric field is W. How much electrostatic work is done on a particle carrying charge -2q that travels from B to A in the field?

Find the power dissipated in a $25~\Omega$ electric heater connected to a $120~\mathrm{V}$ outlet.