A 2.0 micro Farad capacitor in a circuit in series with a resistance of 1.0 mega ohms is charged with a 6.0v battery. How long would it take to chage the capacitor to three fourths of its maximum voltage.

Answer 1

U =U₀exp(-t/RC)
U/U₀ =exp(-t/RC)

ln(U/U₀) = -t/RC
t= - RC ln(U/U₀) =
= - 1•10⁶•2•10⁻⁶•ln(0.75•6/6)=0.58 s