Q2

Quina ha de ser la ddp entre el càtode i l'ànode d'un CRT per a què els electrons adquireixin una velocitat de 10.000 km·s-1.

La velocitat dels electrons en el SI és:

v equals 10000 space begin inline style fraction numerator k m over denominator s end fraction end style equals 10 to the power of 7 space begin inline style m over s end style


I la ddp serà:

increment E subscript p equals negative increment E subscript c equals negative left parenthesis 1 half times m times v squared minus 1 half times m times v subscript o superscript 2 right parenthesis equals negative 1 half times m times v squared

q times increment V equals negative 1 half times m times v squared

negative 1 comma 6 times 10 to the power of negative 19 end exponent times increment V equals negative 1 half times 9 comma 1 times 10 to the power of negative 31 end exponent times left parenthesis 10 to the power of 7 right parenthesis squared

box enclose increment V equals 284 space V end enclose