Force on Moving Charges & Right Hand Rule Video Lessons

Concept

# Problem: An electron in a TV CRT moves with a speed of 6.00 × 107 m/s, in a direction perpendicular to the Earth's field, which has a strength of 6.00 × 10–5 T.(a) What strength electric field must be applied perpendicular to the Earth's field to make the electron moves in a straight line?(b) If this is done between plates separated by 1.00 cm, what is the voltage applied? (Note that TVs are usually surrounded by a ferromagnetic material to shield against external magnetic fields and avoid the need for such a correction.)

###### FREE Expert Solution

Electric force:

$\overline{){{\mathbf{F}}}_{{\mathbf{E}}}{\mathbf{=}}{\mathbf{q}}{\mathbf{E}}}$

Magnetic force on moving charge:

$\overline{){{\mathbf{F}}}_{{\mathbf{B}}}{\mathbf{=}}{\mathbf{q}}{\mathbf{v}}{\mathbf{B}}{\mathbf{s}}{\mathbf{i}}{\mathbf{n}}{\mathbf{\theta }}}$

(a)

The electron moves straight when the net force on the electron is zero. The electric force opposes the magnetic force:

ΣF = ma

###### Problem Details

An electron in a TV CRT moves with a speed of 6.00 × 107 m/s, in a direction perpendicular to the Earth's field, which has a strength of 6.00 × 10–5 T.

(a) What strength electric field must be applied perpendicular to the Earth's field to make the electron moves in a straight line?

(b) If this is done between plates separated by 1.00 cm, what is the voltage applied? (Note that TVs are usually surrounded by a ferromagnetic material to shield against external magnetic fields and avoid the need for such a correction.)

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