Physics 9702 · AS & A Level · Force on a moving charge

Force on a moving charge — practice question

(a(i))[2]

A particle of mass $m$, charge $+q$ and speed $v$ is moving in the same direction as a uniform gravitational field of field strength $g$. State the magnitude and direction of any force acting on the particle.

(a(ii))[1]

A particle has mass $m$, charge $+q$ and speed $v$. State the magnitude and direction of any force acting on the particle when the particle is moving along the direction of a uniform magnetic field of flux density $B$.

(b(i))[2]

Two charged horizontal metal plates, in a vacuum, create a uniform electric field of field strength $E$ between the plates. Outside the region between the plates, the field strength is zero. A particle enters the electric field at right-angles to the field direction, as shown in Fig. 6.1. A uniform magnetic field is to be applied in the same region as the electric field so that the particle passes undeviated through the region between the plates. State and explain the direction of the magnetic field.

(b(ii))[3]

Derive, with explanation, the relationship between speed $v$ and the magnitudes of electric field strength $E$ and magnetic flux density $B$.

(c)[2]

A second particle has the same mass $m$ and charge $+q$ as the particle in (b), but its speed is $2v$. It enters the region between the plates in the same direction as the particle in (b). On Fig. 6.1, sketch the path of this particle through the region between the plates.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Magnitude of force $= mg$

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