(a)
(i)
Define electric field.
[ 1 ]
[Maximum number: 1]
A tiny oil droplet with mass is at rest in an electric field of electric field strength , as shown.
The weight of the droplet is exactly balanced by the electrical force on the droplet.
What is the charge on the droplet?
A
B
C
D
[Maximum number: 1]
The diagrams show a negative electric charge situated in a uniform electric field and a mass situated in a uniform gravitational field.
Which row shows the directions of the forces acting on the charge and on the mass?
charge
mass
(a)
Two point charges A and B are separated by a distance of 20 nm in a vacuum, as illustrated in Fig. 3.1.
Fig. 3.1
A point P is a distance x from A along the line A B.
The variation with distance x of the electric potential due to charge A alone is shown in Fig. 3.2.
Fig. 3.2
The variation with distance x of the electric potential due to charge B alone is also shown in Fig. 3.2.
[ 2 ]
(i)
State and explain whether the charges A and B are of the same, or opposite, sign.
[ 2 ]
[Maximum number: 1]
A particle is in a uniform field. The particle experiences a force in the opposite direction to the field.
Which field is the particle in, and on which property of the particle is the field acting?
field
property of particle
on which the field acts
electric
charge
electric
current
gravitational
mass
gravitational
weight
(a)
State what is meant by a line of force in
[ 2 ]
(i)
an electric field.
[ 2 ]
(a)
Define electric field strength.
(a)
Two charged metal spheres A and B are situated in a vacuum, as illustrated in Fig. 4.1.
Fig. 4.1
The shortest distance between the surfaces of the spheres is 6.0 cm .
A movable point P lies along the line joining the centres of the two spheres, a distance x from the surface of sphere A.
The variation with distance x of the electric field E at point P is shown in Fig. 4.2.
Fig. 4.2
[ 2 ]
(i)
Use Fig. 4.2 to explain whether the two spheres have charges of the same, or opposite, sign.
[ 2 ]
(a)
Define electric field strength.
(a)
Define electric field strength.
[ 1 ]
(b)
Two horizontal metal plates are 14 mm apart in a vacuum. A potential difference (p.d.) of 1.9 kV is applied across the plates, as shown in Fig. 3.1.
Fig. 3.1
A uniform electric field is produced between the plates.
The sphere S in (b) is charged and is held stationary between the plates by the electric field.
[ 4 ]
(i)
Calculate the magnitude of the charge on S .
charge = ..... C
[ 2 ]
(ii)
The magnitude of the p.d. applied to the plates is increased.
Explain why S accelerates towards the top plate.
[ 2 ]