theo de ta co:

\(\dfrac{1}{5}X=\dfrac{1}{4}.64\)

\(\Rightarrow X=16:\dfrac{1}{5}=80\left(dvC\right)\)

=> X la Br

TT: R = 12\(\Omega\) ; U = 12V ; t = 1s

=> Q = ?

GIAI:

nhiet luong toa ra tren day dan la:

\(Q=I^2.R.t=\left(\dfrac{U}{R}\right)^2.R.t=\dfrac{U^2}{R}.t=\dfrac{12^2}{12}.1=12\left(J\right)\)

TT: l = 20m ; S = 0,05mm² = 5.10^-8 m²

p = 0,4.10^-6 \(\Omega m\) => R=?

GIAI:

dien tro cua day dan la:

\(R=\dfrac{l.p}{S}=\dfrac{20.0,4.10^{-6}}{5.10^{-8}}=160\left(\Omega\right)\)

số bé là:

  (10x2)-11=9