Crossed fields: only one speed goes straight

Year 12 Physics · plates horizontal, E down between them, B into the page, particle entering from the left · F = q(E + v × B) · balance at v = E/B, whatever the charge or mass

Which field is switched on:

Electric field E 4.0 kV m⁻¹

Magnetic field B 0.020 T

Entry speed v 1.5 × 10⁵ m s⁻¹

Field region

F_E · F_B · path

Press Fire with E only, then with B only, and compare the two shapes. Then switch to Crossed fields and hunt for the speed that goes straight through.

Live readouts

speed—

F_E—

F_B—

resultant—

balance speed E/B—

deflection—

gyroradius—

entry speed—

exit speed—

no shot yet

Ready. Choose a field mode, set the sliders and press Fire.