How Long Does It Take for a Condenser's Voltage to Drop by 90%?

[Gspace]

1. Homework Statement

When a condenser discharges electricity, the instantaneous rate of change of the voltage is proportional to the voltage in the condenser. Suppose you have a discharging condenser and the instantaneous rate of change of the voltage is -0.01 of the voltage (in volts per second). How many seconds does it take for the voltage to decrease by 90%?

2. Homework Equations

E^rt

3. The Attempt at a Solution

E^(-0.01(0.90))=0.99104


Help Please!

 

[Nino MMP]

I don't know what the E is supposed to be. E is the voltage of the condenser so you can rewrite the equation as Voltage0.99104=Voltagee^(-0.01t) Take the natural log of both sides ln(Voltage0.99104)=ln(Voltagee^(-0.01t)) ln(Voltage0.99104)= -0.01t + ln(Voltage) -ln(Voltage0.99104)+ln(Voltage)=-0.01t t=-[ln(Voltage0.99104)-ln(Voltage)]/0.01