Electric force between point charges

Two point charges A and B each carry a charge of $+6.4 \times 10^{-19}\,\text{C}$. They are in a vacuum and are separated by a distance of $12.0\,\mu\text{m}$, as illustrated in Fig. 4.1. Points P and Q lie on the line AB. Point P is $3.0\,\mu\text{m}$ from charge A, while point Q is $3.0\,\mu\text{m}$ from charge B.

May/June 2010

Two point charges A and B each carry a charge of $+6.4 \times 10^{-19}\,\text{C}$. The charges lie in a vacuum and are $12.0\,\mu\text{m}$ apart, as illustrated in Fig. 4.1. Points P and Q lie on the straight line AB. Point P is $3.0\,\mu\text{m}$ from charge A, while point Q is $3.0\,\mu\text{m}$ from charge B.

May/June 2010

Section A. Complete every question in the spaces provided.

May/June 2011

Section A: Answer every question in the spaces given.

May/June 2011

A helium nucleus has two protons. In a simplified model of the helium nucleus, each proton is treated as a charged point mass. The gap between these point masses is assumed to be $2.0 \times 10^{-15}\,\text{m}$.

May/June 2014

Using electric field lines, explain why the charge on an isolated spherical conductor can be regarded as a point charge at its centre for points outside the sphere.

May/June 2016

An $\alpha$-particle is moving through a vacuum towards the middle of a gold nucleus, as shown in Fig. 5.1. The gold nucleus carries charge $79e$. Both the gold nucleus and the $\alpha$-particle may be treated as point charges. When the $\alpha$-particle is a large distance from the gold nucleus, its energy is $7.7 \times 10^{-13}\,\text{J}$.

May/June 2017

State Coulomb’s law for point charges.

May/June 2017

An $\alpha$-particle is moving through a vacuum towards the centre of a gold nucleus, as shown in Fig. 5.1. The gold nucleus carries charge $79e$. The gold nucleus and the $\alpha$-particle may be treated as point charges. When it is very far from the gold nucleus, the $\alpha$-particle has energy $7.7 \times 10^{-13}\,\text{J}$.

May/June 2017

State Coulomb’s law in words.

May/June 2022

A helium atom can be represented by a nucleus with two electrons moving in circular paths on diametrically opposite sides, each with radius $170\,\text{pm}$, as shown in Fig. 2.1.

May/June 2025

A helium atom can be represented as a nucleus with two electrons in circular orbits on opposite sides of it, each orbit having radius $170\,\text{pm}$, as shown in Fig. 2.1.

May/June 2025

In vacuum, an $\alpha$-particle and a proton are shown in Fig. 4.1, both initially at rest and separated by $20\ \mu\text{m}$.

Oct/Nov 2013

An $\alpha$-particle and a proton are both at rest in a vacuum, with a separation of $20\ \mu\text{m}$, as depicted in Fig. 4.1.

Oct/Nov 2013

As shown in Fig. 5.1, a charged particle $P$ is in vacuum at distance $x$ from the centre of a charged conducting sphere of radius $r$. For particle $P$ outside the conducting sphere, the sphere’s charge can be treated as a point charge at the centre.

Oct/Nov 2015

A charged particle $P$ is in a vacuum a distance $x$ from the centre of a charged conducting sphere of radius $r$, as shown in Fig. 5.1. For particle $P$ located outside the conducting sphere, the sphere’s charge may be treated as though it were concentrated at the centre.

Oct/Nov 2015

State Coulomb’s law for the force acting between two point charges.

Oct/Nov 2017

State Coulomb’s law describing the force between two point charges.

Oct/Nov 2017

State Coulomb’s law in words.

Oct/Nov 2023

State Coulomb’s law in words.

Oct/Nov 2024