Electric Fields (Edexcel International A Level Physics)

A spark chamber consists of a set of parallel metal plates. It can reveal the path of a high energy particle as shown.

A potential difference of 10.5kV is applied across two adjacent plates as shown below.

Sketch lines to represent the electric field between the plates.

A high energy particle causes ionisation of the atoms in the space between the plates.

i) Show that the force on an ionised atom due to the electric field is about 2.6 × 10^–13 N.

charge on ionised atom = 1.60 × 10^–19 C    

distance between plates = 6.40 mm

(3)

ii) The ionised atom travels 0.2 μm in the direction perpendicular to the plates before colliding with another atom.

Deduce whether the collision could lead to further ionisation.

ionisation energy of atoms = 3.9 × 10^–19 J

(2)

The diagram represents a negative point charge.

Draw field lines to show the electric field around the charge.

The surface of a balloon can become charged by rubbing it against clothing. The charge on the surface of the balloon can be assumed to act as if it was concentrated at the balloon’s centre.

Two balloons are suspended by cotton threads so that they just touch each other as shown in diagram 1. The two balloons are then given an equal negative charge and repel as shown in diagram 2. The dots represent the centre of each balloon.

i) Show that the force of repulsion between the balloons in diagram 2 is about 1 × 10⁻³ N.

mass of each balloon = 1.1 grams

(4)

ii) Show that the charge on each balloon is about 2 × 10⁻⁷ C.

(2)

One balloon is removed and the remaining balloon returns to its original position.

Calculate the electric potential at a distance of 0.30 m from the centre of the remaining balloon.

Electric potential = ...............................