False. Lead xaum muaj graphite (ib daim ntawv ntawm carbon), tsis yog txhuas. Qhov tseeb, tsis zoo li ntau tus neeg ntseeg, cov xaum txhuas tsis tau ua nrog txhuas. … Nyob rau thaum ntxov 1500s, ib tug loj deposit ntawm graphite tau pom nyob rau hauv Cumbria, England.
HB mem hluav lead?
Kev sib xyaw ntawm cov ntawv, piv txwv li, 'HB' txhais tau tias xaum tawv thiab dub. 'HB' xaum yog suav tias yog qhov nruab nrab ntawm cov xaum cov qhab nias.
HB xaum tshuaj lom?
Rau cov uas xav paub tias cov xaum xaum puas muaj tshuaj lom lossis muaj tshuaj lom thiab puas tuaj yeem tau txais tshuaj lom ntawm cov xaum? Lo lus teb yog, 'No.
HB xaum yog dab tsi?
Hnub no graphite sau cores yog kev sib xyaw ntawm graphite thiab av nplaum. Los ntawm kev sib txawv ntawm cov graphite rau av nplaum piv, cov xaum ua haujlwm kho qhov tseem ceeb "hardness" - feem ntau txheeb xyuas los ntawm tus lej (2, 2-1/2 lossis 3) lossis ntawv (HB, 2B, H lossis F).
hom xaum twg muaj txhuas?
Graphite mem hluav(ib txwm hu ua "cov xaum") tsim cov cim grey lossis xim dub uas yooj yim tshem tawm, tab sis txwv tsis pub tiv taus cov dej noo, feem ntau cov tshuaj, hluav taws xob ultraviolet thiab ntuj aging.. Lwm hom cwj mem cores, xws li cov charcoal, feem ntau yog siv los kos duab thiab kos duab.
