CAPE Physics Unit 2 · 2018 · Paper 1 · Question Q33

What is the velocity of a beam of electrons when the simultaneous influence of an electric field of 1.7 \times 10^5\text{ V}\,\text{m}^{-1} and a magnetic field of 5.0 \times 10^{-3}\text{ T}, both perpendicular to the beam and to each other, produces NO deflection of the electrons?

1. (A)2.4 \times 10^7\text{ m}\,\text{s}^{-1}
2. (B)3.4 \times 10^7\text{ m}\,\text{s}^{-1}
3. (C)8.5 \times 10^7\text{ m}\,\text{s}^{-1}
4. (D)2.6 \times 10^8\text{ m}\,\text{s}^{-1}