Two small charged spheres are fixed in a liquid of relative permittivity $3.0$. The charges are $+4.0\ \text{nC}$ and $-6.0\ \text{nC}$ and their separation is $0.080\ \text{m}$.

Two large parallel metal plates are separated by $12\ \text{mm}$. The potential difference between the plates is $240\ \text{V}$. A small particle with charge $+2.0\ \mu\text{C}$ is placed midway between the plates, away from the edges.

Two point charges are fixed in a vacuum. The charges are $+4.0\ \text{nC}$ and $-2.0\ \text{nC}$ and their separation is $0.050\ \text{m}$.

Point $P$ is $0.20\ \text{m}$ from a charge of $+6.0\ \text{nC}$ and $0.10\ \text{m}$ from a charge of $-3.0\ \text{nC}$.

Points $P$ and $Q$ lie on the same equipotential line in an electric field. A small positive charge is moved slowly from $P$ to $Q$ along this line.

Three identical metal spheres on insulating stands are used in two electrostatics procedures. The charge on each sphere is measured before and after contact or grounding.

A pair of large parallel metal plates is connected to a high-voltage supply. A singly charged positive ion is moved from the positive plate to the negative plate through the central uniform region.

A hollow conducting sphere has a positive net charge and is in electrostatic equilibrium. The diagram shows a cross-section of the sphere.

The graph shows the variation of electric potential $V_e$ with position $x$ between two parallel plates. The potential decreases uniformly from $300\ \text{V}$ at $x=0$ to $60\ \text{V}$ at $x=0.080\ \text{m}$.

An electron is moved from a point where the electric potential is $+20\ \text{V}$ to a point where the electric potential is $-30\ \text{V}$.

A hollow conducting sphere of radius $0.15\ \text{m}$ carries a charge of $+5.0\ \text{nC}$. There is no charge inside the hollow region.

Two small conducting spheres carry fixed charges and are placed at different separations. The force sensor records the magnitude of the electrostatic force in air and then with the spheres immersed in an insulating oil.

In a Millikan-type experiment, several oil drops are held stationary between horizontal plates by adjusting the potential difference. The charge calculated for each drop is shown.

A vertical straight wire passes through a horizontal card. Small plotting compasses are placed at different positions around the wire while a steady conventional current flows.

The electric potential is measured at different distances from an isolated point charge. The zero of potential is taken to be at infinity.

A conducting-paper experiment is used to map electric potentials between two metal electrodes of different shapes. Several equipotential lines are drawn from voltmeter readings.

A charged hollow conducting sphere is isolated from its surroundings. Measurements of electric field strength are made at different distances from the centre of the sphere.

Three point charges are fixed at the corners of a triangle. The electric potential energy of the system is found by assembling the charges from infinite separation.

A charged solid conducting sphere is isolated in air. The electric potential is measured along a radial line from the centre of the sphere.

The potential between two parallel plates is measured along a line perpendicular to the plates. Measurements are also taken close to one edge of the plates.

Two small insulating spheres carry charges $+3.2\ \mu\text{C}$ and $-1.8\ \mu\text{C}$. The centres of the spheres are separated by $0.24\ \text{m}$ in air. The spheres may be treated as point charges.

A negatively charged insulating rod is brought near an isolated neutral metal sphere on an insulating stand. A student then connects the sphere briefly to Earth using a conducting wire, removes the wire, and finally removes the rod.

A hollow conducting sphere is mounted on an insulating support. A small positive charge is placed outside the sphere. No charge is placed inside the hollow cavity.

A long straight wire, a circular coil and an air-core solenoid each carry a steady conventional current. A small plotting compass is used to investigate the magnetic field patterns.

A hollow conducting sphere of radius $0.12\ \text{m}$ carries a total charge of $+8.0\ \text{nC}$. There is no charge inside the cavity. The electric potential is defined to be zero at infinity.

Two fixed point charges produce the equipotential pattern shown. A point P is located between the charges, and several field regions are labelled.

In a simplified Millikan-type experiment, an oil drop is held stationary between two horizontal parallel plates separated by $6.0\ \text{mm}$. The potential difference between the plates is $510\ \text{V}$. The effective weight of the drop, including buoyancy correction, is $1.36\times10^{-14}\ \text{N}$.

Two large horizontal parallel plates are separated by $12\ \text{mm}$ and connected to a $1.8\ \text{kV}$ supply. A small bead of mass $2.4\times10^{-6}\ \text{kg}$ carries a charge of $-3.0\ \text{nC}$. The bead is released from rest close to the negative plate.

Three point charges are fixed at the vertices of a right-angled triangle. Charge $A$ is $+4.0\ \mu\text{C}$, charge $B$ is $+2.0\ \mu\text{C}$ and charge $C$ is $-3.0\ \mu\text{C}$. The distances are $AB=0.30\ \text{m}$, $AC=0.40\ \text{m}$ and $BC=0.50\ \text{m}$.

Two fixed point charges lie on a straight line. Charge $Q_1=+6.0\ \mu\text{C}$ is at $x=0$ and charge $Q_2=-2.0\ \mu\text{C}$ is at $x=0.40\ \text{m}$. Point $P$ lies on the line between the two charges.

The graph shows the variation of electric potential $V_e$ with position $x$ along a line between two large parallel plates. Edge effects are negligible.

A conducting-paper experiment is used to map the equipotentials between two long, oppositely charged parallel electrodes. The electrodes are separated by $5.0\ \text{cm}$ and connected to a $10.0\ \text{V}$ supply.

Four identical point charges are fixed at the corners of a square of side $0.20\ \text{m}$. The two charges on the left are $+Q$ and the two charges on the right are $-Q$, where $Q=2.0\ \mu\text{C}$. Point O is at the centre of the square.