IB Physics HL D 3 3 Crossed Electric and Magnetic Fields Questions

Analyse crossed electric and magnetic fields by balancing electric and magnetic forces, selecting velocities and predicting charged-particle paths.

Exam points

Use perpendicular electric and magnetic fields to analyse velocity selection and undeflected charged-particle motion.
Calculate electric or magnetic field strength and determine force balance using E=vB.
Explain trajectories when velocity or particle type changes, including direction of deflection.

[Maximum number: 3]

Two oppositely charged parallel plates are a distance 8.0 cm apart. The potential difference between the plates is 120 V . An alpha particle is placed on the positively charged plate and released from rest. Gravity is ignored.

Figure for Question IB Physics HL D 3 3 Crossed Electric and Magnetic Fields Questions question 1 — IB Physics HL

(a)

A magnetic field directed into the plane of the page is now established between the plates. An alpha particle enters the region between the plates with a horizontal speed of $5.0 \times 10^{5} \mathrm{~m} \mathrm{~s}^{-1}$ . The particle is not deflected.

Calculate the magnitude of the magnetic field.

[ 2 ]

$\begin{aligned} F_{\mathrm{m}} =F_{\mathrm{e}} \text { OR } q v B=q E \text { OR } B=F_{\mathrm{e}} / q v \quad B =\ll \frac{E}{v}=\frac{1.5 \times 10^{3}}{5.0 \times 10^{5}}=>3.0 \times 10^{-3} T \end{aligned}$

Award [2] if $3.0 \times 10^{-3}$ « T » is seen as the answer without working.

Allow ECF from a) and b) i)

□

□

□

(b)

The alpha particle in (c) is replaced by an electron. The electron enters the region between the plates with the same velocity as the alpha particle.

Draw, on the diagram, the path of the electron.

[ 1 ]

All question bank results loaded

IB Physics HL D 3 3 Crossed Electric and Magnetic Fields Questions question 1

Question (a)

Question (b)